Contact Dermatitis

Fragrances are complex organic compounds that are sufficiently volatile to produce an odor—most often a pleasant one—or at times intended to neutralize unpleasant odors. They can be further divided into natural fragrances (eg, essential oils) and synthetic ones. Fragrances are found in abundance in our daily lives: in perfumes; colognes; lotions; shampoos; and an array of other personal, household, and even industrial products (Table). These exposures include products directly applied to the skin, rinsed off, or aerosolized. A single product often contains a multitude of different fragrances to create the scents we know and love. To many, fragrances can be an important part of everyday life or even a part of one’s identity. But that once-intoxicating aroma can transform into an itchy skin nightmare; fragrances are among the most common contact allergens.

Given the widespread prevalence of fragrances in so many products, understanding fragrance allergy and skillful avoidance is imperative. In this review, we explore important aspects of fragrance allergic contact dermatitis (ACD), including chemistry, epidemiology, patch test considerations, and management strategies for patients, with the goal of providing valuable clinical insights for treating physicians on how patients can embrace a fragrance-free lifestyle.

How Fragrances Act as Allergens

A plethora of chemicals emit odors, of which more than 2000 are used to create the fragranced products we see on our shelves today.¹ For many of these fragrances, contact allergy develops because the fragrance acts as a hapten (ie, a small molecule that combines with a carrier protein to elicit an immune response).² Some fragrance molecules require “activation” to be able to bind to proteins; these are known as prehaptens.³ For example, the natural fragrance linalool is generally considered nonallergenic in its initial form. However, once it is exposed to air, it may undergo oxidation to become linalool hydroperoxides, a well-established contact allergen. Some fragrances can become allergenic in the skin itself, often secondary to enzymatic reactions—these are known as prohaptens.³ However, most fragrances are directly reactive to skin proteins on the basis of chemical reactions such as Michael addition and Schiff base formation.⁴ In either case, the end result is that fragrance allergens, including essential oils, may cause skin sensitization and subsequent ACD.^5,6

Epidemiology

Contact allergy to fragrances is not uncommon; in a multicenter cross-sectional study conducted in 5 European countries, the prevalence in the general population was estimated to be as high as 2.6% and 1.9% among 3119 patients patch tested to fragrance mix I (FMI) and fragrance mix II (FMII), respectively.⁷ Studies in patients referred for patch testing have shown a higher 5% to 25% prevalence of fragrance allergy, largely depending on what population was evaluated.¹ Factors such as sociocultural differences in frequency and types of fragrances used could contribute to this variation.

During patch testing, the primary fragrance screening allergens are FMI, FMII, and balsam of Peru (BOP)(Myroxylon pereirae resin).⁷ In recent years, hydroperoxides of linalool and limonene also have emerged as potentially important fragrance allergens.⁸ The frequencies of patch-test positivity of these allergens can be quite high in referral-based populations. In a study performed by the North American Contact Dermatitis Group (NACDG) from 2019 to 2020, frequencies of fragrance allergen positivity were 12.8% for FMI, 5.2% for FMII, 7.4% for BOP, 11.1% for hydroperoxides of linalool, and 3.5% for hydroperoxides of limonene.⁸ Additionally, it was noted that FMI and hydroperoxides of linalool were among the top 10 most frequently positive allergens.⁹ It should be kept in mind that NACDG studies are drawn from a referral population and not representative of the general population.

Allergic contact dermatitis to fragrances can manifest anywhere on the body, but certain patterns are characteristic. A study by the NACDG analyzed fragrance and botanical patch test results in 24,246 patients and found that fragrance/botanical-sensitive patients more commonly had dermatitis involving the face (odds ratio [OR], 1.12; 95% CI, 1.03-1.21), legs (OR, 1.22; 95% CI, 1.06-1.41), and anal/genital areas (OR, 1.26; 95% CI, 1.04-1.52) and were less likely to have hand dermatitis (OR, 0.88; 95% CI, 0.82-0.95) compared with non–fragrance/botanical-sensitive patients.¹⁰ However, other studies have found that hand dermatitis is common among fragrance-allergic individuals.^11-13

Fragrance allergy tends to be more common in women than men, which likely is attributable to differences in product use and exposure.¹⁰ The prevalence of fragrance allergy increases with age in both men and women, peaking at approximately 50 years of age, likely due to repeat exposure or age-related changes to the skin barrier or immune system.¹⁴

Occupational fragrance exposures are important to consider, and fragrance ACD is associated with hairdressers, beauticians, office workers exposed to aromatherapy diffusers, and food handlers.¹⁵ Less-obvious professions that involve exposure to fragrances used to cover up unwanted odors—such as working with industrial and cleaning chemicals or even metalworking—also have been reported to be associated with ACD.¹⁶

Patch Test Considerations

Patch testing is essential to confirm fragrance allergy and guide treatment, but because there are so many potential fragrance allergens, there is no perfect patch test strategy. In a standard patch test series, the most important screening allergens are considered to be FMI, FMII, and BOP; tested together, they are thought to detect a large proportion of cases of fragrance allergy. Strikingly, in a large European study (N=1951), patch testing with the fragrance markers in the baseline panel failed to detect more than 40% of cases of allergy compared to testing with 26 individual fragrance allergens.¹⁷ Other studies have reported that a smaller proportion of fragrance allergies are missed by using baseline screening allergens alone.^18,19 Limonene and linalool hydroperoxides also are potentially important fragrance allergens to consider adding to the patch test panel, as unoxidized limonene and linalool commonly are used in many products and could theoretically undergo auto-oxidation under use conditions.⁸ However, because of the high number of irritant, questionable, and potentially false-positive reactions, the Information Network of Departments of Dermatology has recommended against adding these hydroperoxides to a standard screening tray for patch testing.²⁰ It must be remembered that a positive patch test to a fragrance does not necessarily represent ACD unless the patient has a clinically relevant exposure to the allergen.²¹

In patients who test negative to the baseline ­fragrance-screening allergens and in whom a high degree of suspicion remains, further testing with supplemental fragrance allergens (commercially available from patch test suppliers) is warranted.¹⁷ The thin-layer rapid use epicutaneous (T.R.U.E.) test (SmartPractice) includes FMI and BOP but not FMII or linalool or limonene hydroperoxides. More comprehensive patch test panels are available that include additional fragrances, such as the North American 80 Comprehensive Series and the American Contact Dermatitis Society Core Allergen Series.^22-24 It is important to remain vigilant and consider expanded patch testing if patients initially test negative but suspicion remains.

Furthermore, patch testing with the patient’s own products is an important consideration. Uter et al²⁵ evaluated patch testing using patients’ perfumes, deodorants, and shaving lotions, and approximately 41% (53/129) of patients who tested positive to their own product tested negative for fragrance-screening allergens. Although it can be difficult to ascertain which exact component of a commercial product is the culprit, a positive patch test may still provide clinically relevant information for patients and treating physicians. In cases of questionable or weak-positive results, repeat testing or repeated open application tests can help re-evaluate suspected products.

Cross-reactivity should be considered when patch testing for fragrances. Atwater et al¹⁰ found that cross-reactivity between FMI, FMII, and BOP was common; for instance, approximately 40% of patients testing positive to FMII or BOP also had positive reactions to FMI (522/1182 and 768/1942, respectively). Understanding this concept is important because in some cases (as detailed below) patients will need to avoid all fragrances, not just the ones to which they have previously been exposed, given the limitations on fragrance labeling in the United States. However, this may change with the Modernization of Cosmetic Regulation Act of 2022.²⁶

Avoiding Fragrances: Improving Patient Education and Outcomes

Once a relevant contact allergy to fragrance is established after patch testing, successful avoidance is critical but challenging, as there are numerous potential pitfalls. Missing just 1 hidden source of fragrance exposure will often be the difference between success or failure. Dermatologists play a crucial role in guiding patients through the intricate process of identifying and avoiding potential allergens.

Optimal Safety: Embracing a Fragrance-Free Lifestyle

For fragrance-allergic patients, it generally is safest to completely avoid fragrance.

First, if a patient only shows positive patch-test reactions to fragrance screening mixes (and not to the particular fragrances in these mixes), there is no way to be certain which fragrances the patient needs to avoid.

Second, even if specific fragrance allergens are identified, numerous chemically related fragrances to which the patient may be allergic are not commercially available for patch testing. One review provided evidence of 162 fragrance allergens that have been documented to cause contact allergy.¹ Dermatologists generally patch test to screening mixtures and/or the 26 fragrance chemicals required on labels in European products (European Directive fragrance).²⁷ Therefore, there are more than 100 known fragrance allergens that are not routinely tested to which patients could be allergic.

Third, certain fragrances, such as limonene and linalool, are found in many products with fragrance, and it is difficult to find products without these substances. Limonene and linalool themselves are not potent allergens; however, upon air exposure, they may auto-oxidize to hydroperoxides of limonene and linalool, which are increasingly common positive patch tests.¹⁹

Additionally, patients should be advised that many products labeled “fragrance free,” “unscented,” or “free and clear” are not truly fragrance free, and patients should not choose products based on these claims. There are no legal definitions for these claims in the United States, and industries are allowed to choose the definition they prefer. Numerous products labeled “unscented” use this term to indicate that the product had an odor, the company used a masking fragrance to hide the odor, and then the product can be considered unscented. In many holistic stores, most products labeled “fragrance free” are only free of artificial fragrances but contain essential oils. Of the 162 documented fragrance allergens, 80 are essential oils.⁶ Essential oils are perceived to be safe by the vast majority of the population because they are viewed as “natural” and “unprocessed” sources of fragrance.²⁸ However, numerous allergenic terpenes have been discovered in essential oils, including functionalized variations of alcohols (eg, geraniol, bisabolol) and aldehydes (eg, citronellal).⁶ Essential oils also consist of nonterpenic compounds produced through the phenylpropanoids pathway, including eugenol and cinnamaldehyde. One review showed that most essential oils contain one or more European Directive fragrance.²⁹ Therefore, many products labeled “unscented,” “fragrance free,” or “natural” are not free of fragrance and may be unsafe for fragrance-allergic patients.

Although not required, manufacturers sometimes voluntarily list one or more of the 162 currently identified fragrance allergens on product labels. Also, there are more than 50 potentially allergenic essential oils that can be listed on labels by their common names or by genus or species. In addition, there are synonyms for fragrance, such as aroma, parfum, perfume, and scent. Therefore, there are several hundred different ingredient names on labels that indicate the presence of fragrance, and patients are very unlikely to successfully identify fragrance-free products by trying to read product labels on their own.

Lastly, in the United States product labels only require products to state that they contain “fragrance” and do not mandate the listing of specific fragrances. If a patient is allergic to a specific fragrance, there is no way to determine if that fragrance is present in these products. This will change with the enactment of Modernization of Cosmetics Regulation Act of 2022, which empowers the US Food and Drug Administration to require manufacturers to disclose many, but not all, fragrance allergens on the labels of cosmetic and topical products.²⁶

For all these reasons, patients should be advised to use a medical database to choose safe alternative products instead of trying to read labels themselves to avoid fragrance. The American Contact Dermatitis Society’s Contact Allergen Management Program (CAMP) database (https://www.contactderm.org/resources/acds-camp) is designed to identify safe alternative products for patients with contact allergies. When CAMP is programmed to avoid “fragrance,” it will list only “safe” products free of all fragrances found in a comprehensive fragrance cross-reactor group.³⁰ This customizable database is available as an application that can be downloaded onto a patient’s mobile device. Fragrance-allergic patients should be encouraged to use the CAMP application or other similar applications (eg, SkinSAFE)(https://www.skinsafeproducts­.com/) to find all the products they use.

Potential Pitfalls in Fragrance Avoidance

Most physicians, even dermatologists, will not know which products on the market are fragrance free from a contact allergy standpoint. Patients should instruct their physicians to use the allergen-avoidance application of choice whenever recommending new topical products, whether prescription or nonprescription. In 2009, Nardelli and colleagues³¹ found that 10% of topical pharmaceutical products contained a total of 66 different fragrance substances.

Individuals who are allergic to fragrance also can react to fragrances used by close contacts (ie, consort dermatitis).³² Therefore, fragrance-allergic individuals who do not improve after changing their personal products should consider urging their spouses or significant others to choose their personal care products using an allergen-avoidance application. Also, physical contact with pets can cause reactions, and the use of a fragrance-free pet shampoo is recommended. Additionally, allergic individuals who are providing care for small children should select fragrance-free products for them.

Some of the most heavily fragranced products on the market are found at hair salons. One exposure to an allergen often can keep patients broken out for up to 4 weeks and occasionally longer, a typical frequency for salon visits—even if the individual is taking great care to avoid fragrance at home. Patients should be instructed to bring their own shampoo, conditioner, and styling products to the salon. These patients also should bring safe moisturizer and nail polish remover for manicures. Additionally, aromatherapy used in most massages can cause flare-ups, and it is recommended that allergic patients purchase fragrance-free massage oil to bring to their sessions.

Fragranced soaps and cleansers can leave a residue on the palmar surface of the hands and fingers. This residue may not meet the threshold for causing a reaction on the thick skin of these surfaces, but it is sufficient to passively transfer fragrance to other more sensitive areas, such as the eyelids. Passive transfer of fragrance can be a major source of allergen exposure and should not be overlooked. Allergic patients should be instructed to bring safe hand cleansers to friends’ houses, restaurants, or work.

Airborne fragrances in a patient’s environment can reach sufficient concentration to cause airborne contact dermatitis. In one case report, an Uber driver developed facial airborne ACD from a fragrance diffuser in his vehicle and his condition improved upon removing the diffuser.³³ Therefore, patients should be instructed to avoid fragranced diffusers, scented candles, room deodorizers, incense, and wax melts.

Fragrance in household products also can be an issue. Fragrance-allergic patients should be instructed to choose fragrance-free cleaning products and to avoid fragranced wipes on surfaces that may be touched. In addition, they should be instructed to use fragrance-free laundry products. It is not required for household products in the United States to list their ingredients, and the majority do not have complete ingredient lists. Therefore, it is imperative that the patient use an allergen-avoidance application that identifies products that have full ingredient disclosure and are free of fragrance.

For individuals who enjoy perfume and/or cologne, it may be possible for them to resume use of these products in some cases after their condition has fully cleared with complete fragrance avoidance. They should avoid spraying products into the air or applying them directly onto the skin and should instead dip a cotton swab into the perfume/cologne and dab a small amount onto their clothing. This technique can sometimes satisfy the patient and improve compliance.

If a patient who is allergic to fragrance does not clear after 6 weeks of complete fragrance avoidance, it is worth considering systemic contact dermatitis due to ingestion of fragrance-related substances in foods.³⁴ A large number of fragrance materials also are food flavorings. For patients allergic to a specific fragrance(s), systemic avoidance needs to be specific to the allergen, and the Flavor and Extract Manufacturers Association’s flavor ingredient library is most helpful (https://www.femaflavor.org/flavor-library). If the patient is allergic to the complex mixture BOP, a balsam-free diet can be attempted.^35,36

Final Thoughts

Dermatologists must equip themselves with the knowledge to educate fragrance-allergic patients on proper avoidance. The multifaceted nature of fragrance avoidance requires a personalized approach, combining label scrutiny, utilization of a safe-product application, and tailored recommendations for specific situations. By guiding patients through these complexities, dermatologists can empower patients to manage their fragrance allergy and enhance their quality of life.

Fragrances are complex organic compounds that are sufficiently volatile to produce an odor—most often a pleasant one—or at times intended to neutralize unpleasant odors. They can be further divided into natural fragrances (eg, essential oils) and synthetic ones. Fragrances are found in abundance in our daily lives: in perfumes; colognes; lotions; shampoos; and an array of other personal, household, and even industrial products (Table). These exposures include products directly applied to the skin, rinsed off, or aerosolized. A single product often contains a multitude of different fragrances to create the scents we know and love. To many, fragrances can be an important part of everyday life or even a part of one’s identity. But that once-intoxicating aroma can transform into an itchy skin nightmare; fragrances are among the most common contact allergens.

Given the widespread prevalence of fragrances in so many products, understanding fragrance allergy and skillful avoidance is imperative. In this review, we explore important aspects of fragrance allergic contact dermatitis (ACD), including chemistry, epidemiology, patch test considerations, and management strategies for patients, with the goal of providing valuable clinical insights for treating physicians on how patients can embrace a fragrance-free lifestyle.

How Fragrances Act as Allergens

A plethora of chemicals emit odors, of which more than 2000 are used to create the fragranced products we see on our shelves today.¹ For many of these fragrances, contact allergy develops because the fragrance acts as a hapten (ie, a small molecule that combines with a carrier protein to elicit an immune response).² Some fragrance molecules require “activation” to be able to bind to proteins; these are known as prehaptens.³ For example, the natural fragrance linalool is generally considered nonallergenic in its initial form. However, once it is exposed to air, it may undergo oxidation to become linalool hydroperoxides, a well-established contact allergen. Some fragrances can become allergenic in the skin itself, often secondary to enzymatic reactions—these are known as prohaptens.³ However, most fragrances are directly reactive to skin proteins on the basis of chemical reactions such as Michael addition and Schiff base formation.⁴ In either case, the end result is that fragrance allergens, including essential oils, may cause skin sensitization and subsequent ACD.^5,6

Epidemiology

Contact allergy to fragrances is not uncommon; in a multicenter cross-sectional study conducted in 5 European countries, the prevalence in the general population was estimated to be as high as 2.6% and 1.9% among 3119 patients patch tested to fragrance mix I (FMI) and fragrance mix II (FMII), respectively.⁷ Studies in patients referred for patch testing have shown a higher 5% to 25% prevalence of fragrance allergy, largely depending on what population was evaluated.¹ Factors such as sociocultural differences in frequency and types of fragrances used could contribute to this variation.

During patch testing, the primary fragrance screening allergens are FMI, FMII, and balsam of Peru (BOP)(Myroxylon pereirae resin).⁷ In recent years, hydroperoxides of linalool and limonene also have emerged as potentially important fragrance allergens.⁸ The frequencies of patch-test positivity of these allergens can be quite high in referral-based populations. In a study performed by the North American Contact Dermatitis Group (NACDG) from 2019 to 2020, frequencies of fragrance allergen positivity were 12.8% for FMI, 5.2% for FMII, 7.4% for BOP, 11.1% for hydroperoxides of linalool, and 3.5% for hydroperoxides of limonene.⁸ Additionally, it was noted that FMI and hydroperoxides of linalool were among the top 10 most frequently positive allergens.⁹ It should be kept in mind that NACDG studies are drawn from a referral population and not representative of the general population.

Allergic contact dermatitis to fragrances can manifest anywhere on the body, but certain patterns are characteristic. A study by the NACDG analyzed fragrance and botanical patch test results in 24,246 patients and found that fragrance/botanical-sensitive patients more commonly had dermatitis involving the face (odds ratio [OR], 1.12; 95% CI, 1.03-1.21), legs (OR, 1.22; 95% CI, 1.06-1.41), and anal/genital areas (OR, 1.26; 95% CI, 1.04-1.52) and were less likely to have hand dermatitis (OR, 0.88; 95% CI, 0.82-0.95) compared with non–fragrance/botanical-sensitive patients.¹⁰ However, other studies have found that hand dermatitis is common among fragrance-allergic individuals.^11-13

Fragrance allergy tends to be more common in women than men, which likely is attributable to differences in product use and exposure.¹⁰ The prevalence of fragrance allergy increases with age in both men and women, peaking at approximately 50 years of age, likely due to repeat exposure or age-related changes to the skin barrier or immune system.¹⁴

Occupational fragrance exposures are important to consider, and fragrance ACD is associated with hairdressers, beauticians, office workers exposed to aromatherapy diffusers, and food handlers.¹⁵ Less-obvious professions that involve exposure to fragrances used to cover up unwanted odors—such as working with industrial and cleaning chemicals or even metalworking—also have been reported to be associated with ACD.¹⁶

Patch Test Considerations

Patch testing is essential to confirm fragrance allergy and guide treatment, but because there are so many potential fragrance allergens, there is no perfect patch test strategy. In a standard patch test series, the most important screening allergens are considered to be FMI, FMII, and BOP; tested together, they are thought to detect a large proportion of cases of fragrance allergy. Strikingly, in a large European study (N=1951), patch testing with the fragrance markers in the baseline panel failed to detect more than 40% of cases of allergy compared to testing with 26 individual fragrance allergens.¹⁷ Other studies have reported that a smaller proportion of fragrance allergies are missed by using baseline screening allergens alone.^18,19 Limonene and linalool hydroperoxides also are potentially important fragrance allergens to consider adding to the patch test panel, as unoxidized limonene and linalool commonly are used in many products and could theoretically undergo auto-oxidation under use conditions.⁸ However, because of the high number of irritant, questionable, and potentially false-positive reactions, the Information Network of Departments of Dermatology has recommended against adding these hydroperoxides to a standard screening tray for patch testing.²⁰ It must be remembered that a positive patch test to a fragrance does not necessarily represent ACD unless the patient has a clinically relevant exposure to the allergen.²¹

In patients who test negative to the baseline ­fragrance-screening allergens and in whom a high degree of suspicion remains, further testing with supplemental fragrance allergens (commercially available from patch test suppliers) is warranted.¹⁷ The thin-layer rapid use epicutaneous (T.R.U.E.) test (SmartPractice) includes FMI and BOP but not FMII or linalool or limonene hydroperoxides. More comprehensive patch test panels are available that include additional fragrances, such as the North American 80 Comprehensive Series and the American Contact Dermatitis Society Core Allergen Series.^22-24 It is important to remain vigilant and consider expanded patch testing if patients initially test negative but suspicion remains.

Furthermore, patch testing with the patient’s own products is an important consideration. Uter et al²⁵ evaluated patch testing using patients’ perfumes, deodorants, and shaving lotions, and approximately 41% (53/129) of patients who tested positive to their own product tested negative for fragrance-screening allergens. Although it can be difficult to ascertain which exact component of a commercial product is the culprit, a positive patch test may still provide clinically relevant information for patients and treating physicians. In cases of questionable or weak-positive results, repeat testing or repeated open application tests can help re-evaluate suspected products.

Cross-reactivity should be considered when patch testing for fragrances. Atwater et al¹⁰ found that cross-reactivity between FMI, FMII, and BOP was common; for instance, approximately 40% of patients testing positive to FMII or BOP also had positive reactions to FMI (522/1182 and 768/1942, respectively). Understanding this concept is important because in some cases (as detailed below) patients will need to avoid all fragrances, not just the ones to which they have previously been exposed, given the limitations on fragrance labeling in the United States. However, this may change with the Modernization of Cosmetic Regulation Act of 2022.²⁶

Avoiding Fragrances: Improving Patient Education and Outcomes

Once a relevant contact allergy to fragrance is established after patch testing, successful avoidance is critical but challenging, as there are numerous potential pitfalls. Missing just 1 hidden source of fragrance exposure will often be the difference between success or failure. Dermatologists play a crucial role in guiding patients through the intricate process of identifying and avoiding potential allergens.

Optimal Safety: Embracing a Fragrance-Free Lifestyle

For fragrance-allergic patients, it generally is safest to completely avoid fragrance.

First, if a patient only shows positive patch-test reactions to fragrance screening mixes (and not to the particular fragrances in these mixes), there is no way to be certain which fragrances the patient needs to avoid.

Second, even if specific fragrance allergens are identified, numerous chemically related fragrances to which the patient may be allergic are not commercially available for patch testing. One review provided evidence of 162 fragrance allergens that have been documented to cause contact allergy.¹ Dermatologists generally patch test to screening mixtures and/or the 26 fragrance chemicals required on labels in European products (European Directive fragrance).²⁷ Therefore, there are more than 100 known fragrance allergens that are not routinely tested to which patients could be allergic.

Third, certain fragrances, such as limonene and linalool, are found in many products with fragrance, and it is difficult to find products without these substances. Limonene and linalool themselves are not potent allergens; however, upon air exposure, they may auto-oxidize to hydroperoxides of limonene and linalool, which are increasingly common positive patch tests.¹⁹

Additionally, patients should be advised that many products labeled “fragrance free,” “unscented,” or “free and clear” are not truly fragrance free, and patients should not choose products based on these claims. There are no legal definitions for these claims in the United States, and industries are allowed to choose the definition they prefer. Numerous products labeled “unscented” use this term to indicate that the product had an odor, the company used a masking fragrance to hide the odor, and then the product can be considered unscented. In many holistic stores, most products labeled “fragrance free” are only free of artificial fragrances but contain essential oils. Of the 162 documented fragrance allergens, 80 are essential oils.⁶ Essential oils are perceived to be safe by the vast majority of the population because they are viewed as “natural” and “unprocessed” sources of fragrance.²⁸ However, numerous allergenic terpenes have been discovered in essential oils, including functionalized variations of alcohols (eg, geraniol, bisabolol) and aldehydes (eg, citronellal).⁶ Essential oils also consist of nonterpenic compounds produced through the phenylpropanoids pathway, including eugenol and cinnamaldehyde. One review showed that most essential oils contain one or more European Directive fragrance.²⁹ Therefore, many products labeled “unscented,” “fragrance free,” or “natural” are not free of fragrance and may be unsafe for fragrance-allergic patients.

Although not required, manufacturers sometimes voluntarily list one or more of the 162 currently identified fragrance allergens on product labels. Also, there are more than 50 potentially allergenic essential oils that can be listed on labels by their common names or by genus or species. In addition, there are synonyms for fragrance, such as aroma, parfum, perfume, and scent. Therefore, there are several hundred different ingredient names on labels that indicate the presence of fragrance, and patients are very unlikely to successfully identify fragrance-free products by trying to read product labels on their own.

Lastly, in the United States product labels only require products to state that they contain “fragrance” and do not mandate the listing of specific fragrances. If a patient is allergic to a specific fragrance, there is no way to determine if that fragrance is present in these products. This will change with the enactment of Modernization of Cosmetics Regulation Act of 2022, which empowers the US Food and Drug Administration to require manufacturers to disclose many, but not all, fragrance allergens on the labels of cosmetic and topical products.²⁶

For all these reasons, patients should be advised to use a medical database to choose safe alternative products instead of trying to read labels themselves to avoid fragrance. The American Contact Dermatitis Society’s Contact Allergen Management Program (CAMP) database (https://www.contactderm.org/resources/acds-camp) is designed to identify safe alternative products for patients with contact allergies. When CAMP is programmed to avoid “fragrance,” it will list only “safe” products free of all fragrances found in a comprehensive fragrance cross-reactor group.³⁰ This customizable database is available as an application that can be downloaded onto a patient’s mobile device. Fragrance-allergic patients should be encouraged to use the CAMP application or other similar applications (eg, SkinSAFE)(https://www.skinsafeproducts­.com/) to find all the products they use.

Potential Pitfalls in Fragrance Avoidance

Most physicians, even dermatologists, will not know which products on the market are fragrance free from a contact allergy standpoint. Patients should instruct their physicians to use the allergen-avoidance application of choice whenever recommending new topical products, whether prescription or nonprescription. In 2009, Nardelli and colleagues³¹ found that 10% of topical pharmaceutical products contained a total of 66 different fragrance substances.

Individuals who are allergic to fragrance also can react to fragrances used by close contacts (ie, consort dermatitis).³² Therefore, fragrance-allergic individuals who do not improve after changing their personal products should consider urging their spouses or significant others to choose their personal care products using an allergen-avoidance application. Also, physical contact with pets can cause reactions, and the use of a fragrance-free pet shampoo is recommended. Additionally, allergic individuals who are providing care for small children should select fragrance-free products for them.

Some of the most heavily fragranced products on the market are found at hair salons. One exposure to an allergen often can keep patients broken out for up to 4 weeks and occasionally longer, a typical frequency for salon visits—even if the individual is taking great care to avoid fragrance at home. Patients should be instructed to bring their own shampoo, conditioner, and styling products to the salon. These patients also should bring safe moisturizer and nail polish remover for manicures. Additionally, aromatherapy used in most massages can cause flare-ups, and it is recommended that allergic patients purchase fragrance-free massage oil to bring to their sessions.

Fragranced soaps and cleansers can leave a residue on the palmar surface of the hands and fingers. This residue may not meet the threshold for causing a reaction on the thick skin of these surfaces, but it is sufficient to passively transfer fragrance to other more sensitive areas, such as the eyelids. Passive transfer of fragrance can be a major source of allergen exposure and should not be overlooked. Allergic patients should be instructed to bring safe hand cleansers to friends’ houses, restaurants, or work.

Airborne fragrances in a patient’s environment can reach sufficient concentration to cause airborne contact dermatitis. In one case report, an Uber driver developed facial airborne ACD from a fragrance diffuser in his vehicle and his condition improved upon removing the diffuser.³³ Therefore, patients should be instructed to avoid fragranced diffusers, scented candles, room deodorizers, incense, and wax melts.

Fragrance in household products also can be an issue. Fragrance-allergic patients should be instructed to choose fragrance-free cleaning products and to avoid fragranced wipes on surfaces that may be touched. In addition, they should be instructed to use fragrance-free laundry products. It is not required for household products in the United States to list their ingredients, and the majority do not have complete ingredient lists. Therefore, it is imperative that the patient use an allergen-avoidance application that identifies products that have full ingredient disclosure and are free of fragrance.

For individuals who enjoy perfume and/or cologne, it may be possible for them to resume use of these products in some cases after their condition has fully cleared with complete fragrance avoidance. They should avoid spraying products into the air or applying them directly onto the skin and should instead dip a cotton swab into the perfume/cologne and dab a small amount onto their clothing. This technique can sometimes satisfy the patient and improve compliance.

If a patient who is allergic to fragrance does not clear after 6 weeks of complete fragrance avoidance, it is worth considering systemic contact dermatitis due to ingestion of fragrance-related substances in foods.³⁴ A large number of fragrance materials also are food flavorings. For patients allergic to a specific fragrance(s), systemic avoidance needs to be specific to the allergen, and the Flavor and Extract Manufacturers Association’s flavor ingredient library is most helpful (https://www.femaflavor.org/flavor-library). If the patient is allergic to the complex mixture BOP, a balsam-free diet can be attempted.^35,36

Final Thoughts

Dermatologists must equip themselves with the knowledge to educate fragrance-allergic patients on proper avoidance. The multifaceted nature of fragrance avoidance requires a personalized approach, combining label scrutiny, utilization of a safe-product application, and tailored recommendations for specific situations. By guiding patients through these complexities, dermatologists can empower patients to manage their fragrance allergy and enhance their quality of life.

Fragrances are complex organic compounds that are sufficiently volatile to produce an odor—most often a pleasant one—or at times intended to neutralize unpleasant odors. They can be further divided into natural fragrances (eg, essential oils) and synthetic ones. Fragrances are found in abundance in our daily lives: in perfumes; colognes; lotions; shampoos; and an array of other personal, household, and even industrial products (Table). These exposures include products directly applied to the skin, rinsed off, or aerosolized. A single product often contains a multitude of different fragrances to create the scents we know and love. To many, fragrances can be an important part of everyday life or even a part of one’s identity. But that once-intoxicating aroma can transform into an itchy skin nightmare; fragrances are among the most common contact allergens.

Given the widespread prevalence of fragrances in so many products, understanding fragrance allergy and skillful avoidance is imperative. In this review, we explore important aspects of fragrance allergic contact dermatitis (ACD), including chemistry, epidemiology, patch test considerations, and management strategies for patients, with the goal of providing valuable clinical insights for treating physicians on how patients can embrace a fragrance-free lifestyle.

How Fragrances Act as Allergens

A plethora of chemicals emit odors, of which more than 2000 are used to create the fragranced products we see on our shelves today.¹ For many of these fragrances, contact allergy develops because the fragrance acts as a hapten (ie, a small molecule that combines with a carrier protein to elicit an immune response).² Some fragrance molecules require “activation” to be able to bind to proteins; these are known as prehaptens.³ For example, the natural fragrance linalool is generally considered nonallergenic in its initial form. However, once it is exposed to air, it may undergo oxidation to become linalool hydroperoxides, a well-established contact allergen. Some fragrances can become allergenic in the skin itself, often secondary to enzymatic reactions—these are known as prohaptens.³ However, most fragrances are directly reactive to skin proteins on the basis of chemical reactions such as Michael addition and Schiff base formation.⁴ In either case, the end result is that fragrance allergens, including essential oils, may cause skin sensitization and subsequent ACD.^5,6

Epidemiology

Contact allergy to fragrances is not uncommon; in a multicenter cross-sectional study conducted in 5 European countries, the prevalence in the general population was estimated to be as high as 2.6% and 1.9% among 3119 patients patch tested to fragrance mix I (FMI) and fragrance mix II (FMII), respectively.⁷ Studies in patients referred for patch testing have shown a higher 5% to 25% prevalence of fragrance allergy, largely depending on what population was evaluated.¹ Factors such as sociocultural differences in frequency and types of fragrances used could contribute to this variation.

During patch testing, the primary fragrance screening allergens are FMI, FMII, and balsam of Peru (BOP)(Myroxylon pereirae resin).⁷ In recent years, hydroperoxides of linalool and limonene also have emerged as potentially important fragrance allergens.⁸ The frequencies of patch-test positivity of these allergens can be quite high in referral-based populations. In a study performed by the North American Contact Dermatitis Group (NACDG) from 2019 to 2020, frequencies of fragrance allergen positivity were 12.8% for FMI, 5.2% for FMII, 7.4% for BOP, 11.1% for hydroperoxides of linalool, and 3.5% for hydroperoxides of limonene.⁸ Additionally, it was noted that FMI and hydroperoxides of linalool were among the top 10 most frequently positive allergens.⁹ It should be kept in mind that NACDG studies are drawn from a referral population and not representative of the general population.

Allergic contact dermatitis to fragrances can manifest anywhere on the body, but certain patterns are characteristic. A study by the NACDG analyzed fragrance and botanical patch test results in 24,246 patients and found that fragrance/botanical-sensitive patients more commonly had dermatitis involving the face (odds ratio [OR], 1.12; 95% CI, 1.03-1.21), legs (OR, 1.22; 95% CI, 1.06-1.41), and anal/genital areas (OR, 1.26; 95% CI, 1.04-1.52) and were less likely to have hand dermatitis (OR, 0.88; 95% CI, 0.82-0.95) compared with non–fragrance/botanical-sensitive patients.¹⁰ However, other studies have found that hand dermatitis is common among fragrance-allergic individuals.^11-13

Fragrance allergy tends to be more common in women than men, which likely is attributable to differences in product use and exposure.¹⁰ The prevalence of fragrance allergy increases with age in both men and women, peaking at approximately 50 years of age, likely due to repeat exposure or age-related changes to the skin barrier or immune system.¹⁴

Occupational fragrance exposures are important to consider, and fragrance ACD is associated with hairdressers, beauticians, office workers exposed to aromatherapy diffusers, and food handlers.¹⁵ Less-obvious professions that involve exposure to fragrances used to cover up unwanted odors—such as working with industrial and cleaning chemicals or even metalworking—also have been reported to be associated with ACD.¹⁶

Patch Test Considerations

Patch testing is essential to confirm fragrance allergy and guide treatment, but because there are so many potential fragrance allergens, there is no perfect patch test strategy. In a standard patch test series, the most important screening allergens are considered to be FMI, FMII, and BOP; tested together, they are thought to detect a large proportion of cases of fragrance allergy. Strikingly, in a large European study (N=1951), patch testing with the fragrance markers in the baseline panel failed to detect more than 40% of cases of allergy compared to testing with 26 individual fragrance allergens.¹⁷ Other studies have reported that a smaller proportion of fragrance allergies are missed by using baseline screening allergens alone.^18,19 Limonene and linalool hydroperoxides also are potentially important fragrance allergens to consider adding to the patch test panel, as unoxidized limonene and linalool commonly are used in many products and could theoretically undergo auto-oxidation under use conditions.⁸ However, because of the high number of irritant, questionable, and potentially false-positive reactions, the Information Network of Departments of Dermatology has recommended against adding these hydroperoxides to a standard screening tray for patch testing.²⁰ It must be remembered that a positive patch test to a fragrance does not necessarily represent ACD unless the patient has a clinically relevant exposure to the allergen.²¹

In patients who test negative to the baseline ­fragrance-screening allergens and in whom a high degree of suspicion remains, further testing with supplemental fragrance allergens (commercially available from patch test suppliers) is warranted.¹⁷ The thin-layer rapid use epicutaneous (T.R.U.E.) test (SmartPractice) includes FMI and BOP but not FMII or linalool or limonene hydroperoxides. More comprehensive patch test panels are available that include additional fragrances, such as the North American 80 Comprehensive Series and the American Contact Dermatitis Society Core Allergen Series.^22-24 It is important to remain vigilant and consider expanded patch testing if patients initially test negative but suspicion remains.

Furthermore, patch testing with the patient’s own products is an important consideration. Uter et al²⁵ evaluated patch testing using patients’ perfumes, deodorants, and shaving lotions, and approximately 41% (53/129) of patients who tested positive to their own product tested negative for fragrance-screening allergens. Although it can be difficult to ascertain which exact component of a commercial product is the culprit, a positive patch test may still provide clinically relevant information for patients and treating physicians. In cases of questionable or weak-positive results, repeat testing or repeated open application tests can help re-evaluate suspected products.

Cross-reactivity should be considered when patch testing for fragrances. Atwater et al¹⁰ found that cross-reactivity between FMI, FMII, and BOP was common; for instance, approximately 40% of patients testing positive to FMII or BOP also had positive reactions to FMI (522/1182 and 768/1942, respectively). Understanding this concept is important because in some cases (as detailed below) patients will need to avoid all fragrances, not just the ones to which they have previously been exposed, given the limitations on fragrance labeling in the United States. However, this may change with the Modernization of Cosmetic Regulation Act of 2022.²⁶

Avoiding Fragrances: Improving Patient Education and Outcomes

Once a relevant contact allergy to fragrance is established after patch testing, successful avoidance is critical but challenging, as there are numerous potential pitfalls. Missing just 1 hidden source of fragrance exposure will often be the difference between success or failure. Dermatologists play a crucial role in guiding patients through the intricate process of identifying and avoiding potential allergens.

Optimal Safety: Embracing a Fragrance-Free Lifestyle

For fragrance-allergic patients, it generally is safest to completely avoid fragrance.

First, if a patient only shows positive patch-test reactions to fragrance screening mixes (and not to the particular fragrances in these mixes), there is no way to be certain which fragrances the patient needs to avoid.

Second, even if specific fragrance allergens are identified, numerous chemically related fragrances to which the patient may be allergic are not commercially available for patch testing. One review provided evidence of 162 fragrance allergens that have been documented to cause contact allergy.¹ Dermatologists generally patch test to screening mixtures and/or the 26 fragrance chemicals required on labels in European products (European Directive fragrance).²⁷ Therefore, there are more than 100 known fragrance allergens that are not routinely tested to which patients could be allergic.

Third, certain fragrances, such as limonene and linalool, are found in many products with fragrance, and it is difficult to find products without these substances. Limonene and linalool themselves are not potent allergens; however, upon air exposure, they may auto-oxidize to hydroperoxides of limonene and linalool, which are increasingly common positive patch tests.¹⁹

Additionally, patients should be advised that many products labeled “fragrance free,” “unscented,” or “free and clear” are not truly fragrance free, and patients should not choose products based on these claims. There are no legal definitions for these claims in the United States, and industries are allowed to choose the definition they prefer. Numerous products labeled “unscented” use this term to indicate that the product had an odor, the company used a masking fragrance to hide the odor, and then the product can be considered unscented. In many holistic stores, most products labeled “fragrance free” are only free of artificial fragrances but contain essential oils. Of the 162 documented fragrance allergens, 80 are essential oils.⁶ Essential oils are perceived to be safe by the vast majority of the population because they are viewed as “natural” and “unprocessed” sources of fragrance.²⁸ However, numerous allergenic terpenes have been discovered in essential oils, including functionalized variations of alcohols (eg, geraniol, bisabolol) and aldehydes (eg, citronellal).⁶ Essential oils also consist of nonterpenic compounds produced through the phenylpropanoids pathway, including eugenol and cinnamaldehyde. One review showed that most essential oils contain one or more European Directive fragrance.²⁹ Therefore, many products labeled “unscented,” “fragrance free,” or “natural” are not free of fragrance and may be unsafe for fragrance-allergic patients.

Although not required, manufacturers sometimes voluntarily list one or more of the 162 currently identified fragrance allergens on product labels. Also, there are more than 50 potentially allergenic essential oils that can be listed on labels by their common names or by genus or species. In addition, there are synonyms for fragrance, such as aroma, parfum, perfume, and scent. Therefore, there are several hundred different ingredient names on labels that indicate the presence of fragrance, and patients are very unlikely to successfully identify fragrance-free products by trying to read product labels on their own.

Lastly, in the United States product labels only require products to state that they contain “fragrance” and do not mandate the listing of specific fragrances. If a patient is allergic to a specific fragrance, there is no way to determine if that fragrance is present in these products. This will change with the enactment of Modernization of Cosmetics Regulation Act of 2022, which empowers the US Food and Drug Administration to require manufacturers to disclose many, but not all, fragrance allergens on the labels of cosmetic and topical products.²⁶

For all these reasons, patients should be advised to use a medical database to choose safe alternative products instead of trying to read labels themselves to avoid fragrance. The American Contact Dermatitis Society’s Contact Allergen Management Program (CAMP) database (https://www.contactderm.org/resources/acds-camp) is designed to identify safe alternative products for patients with contact allergies. When CAMP is programmed to avoid “fragrance,” it will list only “safe” products free of all fragrances found in a comprehensive fragrance cross-reactor group.³⁰ This customizable database is available as an application that can be downloaded onto a patient’s mobile device. Fragrance-allergic patients should be encouraged to use the CAMP application or other similar applications (eg, SkinSAFE)(https://www.skinsafeproducts­.com/) to find all the products they use.

Potential Pitfalls in Fragrance Avoidance

Most physicians, even dermatologists, will not know which products on the market are fragrance free from a contact allergy standpoint. Patients should instruct their physicians to use the allergen-avoidance application of choice whenever recommending new topical products, whether prescription or nonprescription. In 2009, Nardelli and colleagues³¹ found that 10% of topical pharmaceutical products contained a total of 66 different fragrance substances.

Individuals who are allergic to fragrance also can react to fragrances used by close contacts (ie, consort dermatitis).³² Therefore, fragrance-allergic individuals who do not improve after changing their personal products should consider urging their spouses or significant others to choose their personal care products using an allergen-avoidance application. Also, physical contact with pets can cause reactions, and the use of a fragrance-free pet shampoo is recommended. Additionally, allergic individuals who are providing care for small children should select fragrance-free products for them.

Some of the most heavily fragranced products on the market are found at hair salons. One exposure to an allergen often can keep patients broken out for up to 4 weeks and occasionally longer, a typical frequency for salon visits—even if the individual is taking great care to avoid fragrance at home. Patients should be instructed to bring their own shampoo, conditioner, and styling products to the salon. These patients also should bring safe moisturizer and nail polish remover for manicures. Additionally, aromatherapy used in most massages can cause flare-ups, and it is recommended that allergic patients purchase fragrance-free massage oil to bring to their sessions.

Fragranced soaps and cleansers can leave a residue on the palmar surface of the hands and fingers. This residue may not meet the threshold for causing a reaction on the thick skin of these surfaces, but it is sufficient to passively transfer fragrance to other more sensitive areas, such as the eyelids. Passive transfer of fragrance can be a major source of allergen exposure and should not be overlooked. Allergic patients should be instructed to bring safe hand cleansers to friends’ houses, restaurants, or work.

Airborne fragrances in a patient’s environment can reach sufficient concentration to cause airborne contact dermatitis. In one case report, an Uber driver developed facial airborne ACD from a fragrance diffuser in his vehicle and his condition improved upon removing the diffuser.³³ Therefore, patients should be instructed to avoid fragranced diffusers, scented candles, room deodorizers, incense, and wax melts.

Fragrance in household products also can be an issue. Fragrance-allergic patients should be instructed to choose fragrance-free cleaning products and to avoid fragranced wipes on surfaces that may be touched. In addition, they should be instructed to use fragrance-free laundry products. It is not required for household products in the United States to list their ingredients, and the majority do not have complete ingredient lists. Therefore, it is imperative that the patient use an allergen-avoidance application that identifies products that have full ingredient disclosure and are free of fragrance.

For individuals who enjoy perfume and/or cologne, it may be possible for them to resume use of these products in some cases after their condition has fully cleared with complete fragrance avoidance. They should avoid spraying products into the air or applying them directly onto the skin and should instead dip a cotton swab into the perfume/cologne and dab a small amount onto their clothing. This technique can sometimes satisfy the patient and improve compliance.

If a patient who is allergic to fragrance does not clear after 6 weeks of complete fragrance avoidance, it is worth considering systemic contact dermatitis due to ingestion of fragrance-related substances in foods.³⁴ A large number of fragrance materials also are food flavorings. For patients allergic to a specific fragrance(s), systemic avoidance needs to be specific to the allergen, and the Flavor and Extract Manufacturers Association’s flavor ingredient library is most helpful (https://www.femaflavor.org/flavor-library). If the patient is allergic to the complex mixture BOP, a balsam-free diet can be attempted.^35,36

Final Thoughts

Dermatologists must equip themselves with the knowledge to educate fragrance-allergic patients on proper avoidance. The multifaceted nature of fragrance avoidance requires a personalized approach, combining label scrutiny, utilization of a safe-product application, and tailored recommendations for specific situations. By guiding patients through these complexities, dermatologists can empower patients to manage their fragrance allergy and enhance their quality of life.

Brazilian peppertree (Schinus terebinthifolia), a member of the Anacardiaceae family, is an internationally invasive plant that causes allergic contact dermatitis (ACD) in susceptible individuals. This noxious weed has settled into the landscape of the southern United States and continues to expand. Its key identifying features include its year-round white flowers as well as a peppery and turpentinelike aroma created by cracking its bright red berries. The ACD associated with contact—primarily with the plant’s sap—stems from known alkenyl phenols, cardol and cardanol. Treatment of Brazilian peppertree–associated ACD parallels that for poison ivy. As this pest increases its range, dermatologists living in endemic areas should familiarize themselves with Brazilian peppertree and its potential for harm.

Brazilian Peppertree Morphology and Geography

Plants in the Anacardiaceae family contribute to more ACD than any other family, and its 80 genera include most of the urushiol-containing plants, such as Toxicodendron (poison ivy, poison oak, poison sumac, Japanese lacquer tree), Anacardium (cashew tree), Mangifera (mango fruit), Semecarpus (India marking nut tree), and Schinus (Brazilian peppertree). Deciduous and evergreen tree members of the Anacardiaceae family grow primarily in tropical and subtropical locations and produce thick resins, 5-petalled flowers, and small fruit known as drupes. The genus name for Brazilian peppertree, Schinus, derives from Latin and Greek words meaning “mastic tree,” a relative of the pistachio tree that the Brazilian peppertree resembles.¹ Brazilian peppertree leaves look and smell similar to Pistacia terebinthus (turpentine tree or terebinth), from which the species name terebinthifolia derives.²

Brazilian peppertree originated in South America, particularly Brazil, Paraguay, and Argentina.³ Since the 1840s,⁴ it has been an invasive weed in the United States, notably in Florida, California, Hawaii, Alabama, Georgia,⁵ Arizona,⁶ Nevada,³ and Texas.^5,7 The plant also grows throughout the world, including parts of Africa, Asia, Central America, Europe,⁶ New Zealand,⁸ Australia, and various islands.⁹ The plant expertly outcompetes neighboring plants and has prompted control and eradication efforts in many locations.³

Identifying Features and Allergenic Plant Parts

Brazilian peppertree can be either a shrub or tree up to 30 feet tall.⁴ As an evergreen, it retains its leaves year-round. During fruiting seasons (primarily December through March⁷), bright red or pink (depending on the variety³) berries appear (Figure 1A) and contribute to its nickname “Florida holly.” Although generally considered an unwelcome guest in Florida, it does display white flowers (Figure 1B) year-round, especially from September to November.⁹ It characteristically exhibits 3 to 13 leaflets per leaf.¹⁰ The leaflets’ ovoid and ridged edges, netlike vasculature, shiny hue, and aroma can help identify the plant (Figure 2A). For decades, the sap of the Brazilian peppertree has been associated with skin ­irritation (Figure 2B).⁶ Although the sap of the plant serves as the main culprit of Brazilian peppertree–­associated ACD, it appears that other parts of the plant, including the fruit, can cause irritating effects to skin on contact.^11,12 The leaves, trunk, and fruit can be harmful to both humans and animals.⁶ Chemicals from flowers and crushed fruit also can lead to irritating effects in the respiratory tract if aspirated.¹³

Urushiol, an oily resin present in most plants of the Anacardiaceae family,¹⁴ contains many chemicals, including allergenic phenols, catechols, and resorcinols.¹⁵ Urushiol-allergic individuals develop dermatitis upon exposure to Brazilian peppertree sap.⁶ Alkenyl phenols found in Brazilian peppertree lead to the cutaneous manifestations in sensitized patients.^11,12 In 1983, Stahl et al¹¹ identified a phenol, cardanol (chemical name ­3-pentadecylphenol¹⁶) C15:1, in Brazilian peppertree fruit. The group further tested this compound’s effect on skin via patch testing, which showed an allergic response.¹¹ Cashew nut shells (Anacardium occidentale) contain cardanol, anacardic acid (a phenolic acid), and cardol (a phenol with the chemical name ­5-pentadecylresorcinol),^15,16 though Stahl et al¹¹ were unable to extract these 2 substances (if present) from Brazilian peppertree fruit. When exposed to cardol and anacardic acid, those allergic to poison ivy often develop ACD,¹⁵ and these 2 substances are more irritating than cardanol.¹¹ A later study did identify cardol in addition to cardanol in Brazilian peppertree.¹²

Cutaneous Manifestations

Brazilian peppertree–induced ACD appears similar to other plant-induced ACD with linear streaks of erythema, juicy papules, vesicles, coalescing erythematous plaques, and/or occasional edema and bullae accompanied by intense pruritus.

Treatment

Avoiding contact with Brazilian peppertree is the first line of defense, and treatment for a reaction associated with exposure is similar to that of poison ivy.¹⁷ Application of cool compresses, calamine lotion, and topical astringents offer symptom alleviation, and topical steroids (eg, clobetasol propionate 0.05% twice daily) can improve mild localized ACD when given prior to formation of blisters. For more severe and diffuse ACD, oral steroids (eg, prednisone 1 mg/kg/d tapered over 2–3 weeks) likely are necessary, though intramuscular options greatly alleviate discomfort in more severe cases (eg, intramuscular triamcinolone acetonide 1 mg/kg combined with betamethasone 0.1 mg/kg). Physicians should monitor sites for any signs of superimposed bacterial infection and initiate antibiotics as necessary.¹⁷

Brazilian peppertree (Schinus terebinthifolia), a member of the Anacardiaceae family, is an internationally invasive plant that causes allergic contact dermatitis (ACD) in susceptible individuals. This noxious weed has settled into the landscape of the southern United States and continues to expand. Its key identifying features include its year-round white flowers as well as a peppery and turpentinelike aroma created by cracking its bright red berries. The ACD associated with contact—primarily with the plant’s sap—stems from known alkenyl phenols, cardol and cardanol. Treatment of Brazilian peppertree–associated ACD parallels that for poison ivy. As this pest increases its range, dermatologists living in endemic areas should familiarize themselves with Brazilian peppertree and its potential for harm.

Brazilian Peppertree Morphology and Geography

Plants in the Anacardiaceae family contribute to more ACD than any other family, and its 80 genera include most of the urushiol-containing plants, such as Toxicodendron (poison ivy, poison oak, poison sumac, Japanese lacquer tree), Anacardium (cashew tree), Mangifera (mango fruit), Semecarpus (India marking nut tree), and Schinus (Brazilian peppertree). Deciduous and evergreen tree members of the Anacardiaceae family grow primarily in tropical and subtropical locations and produce thick resins, 5-petalled flowers, and small fruit known as drupes. The genus name for Brazilian peppertree, Schinus, derives from Latin and Greek words meaning “mastic tree,” a relative of the pistachio tree that the Brazilian peppertree resembles.¹ Brazilian peppertree leaves look and smell similar to Pistacia terebinthus (turpentine tree or terebinth), from which the species name terebinthifolia derives.²

Brazilian peppertree originated in South America, particularly Brazil, Paraguay, and Argentina.³ Since the 1840s,⁴ it has been an invasive weed in the United States, notably in Florida, California, Hawaii, Alabama, Georgia,⁵ Arizona,⁶ Nevada,³ and Texas.^5,7 The plant also grows throughout the world, including parts of Africa, Asia, Central America, Europe,⁶ New Zealand,⁸ Australia, and various islands.⁹ The plant expertly outcompetes neighboring plants and has prompted control and eradication efforts in many locations.³

Identifying Features and Allergenic Plant Parts

Brazilian peppertree can be either a shrub or tree up to 30 feet tall.⁴ As an evergreen, it retains its leaves year-round. During fruiting seasons (primarily December through March⁷), bright red or pink (depending on the variety³) berries appear (Figure 1A) and contribute to its nickname “Florida holly.” Although generally considered an unwelcome guest in Florida, it does display white flowers (Figure 1B) year-round, especially from September to November.⁹ It characteristically exhibits 3 to 13 leaflets per leaf.¹⁰ The leaflets’ ovoid and ridged edges, netlike vasculature, shiny hue, and aroma can help identify the plant (Figure 2A). For decades, the sap of the Brazilian peppertree has been associated with skin ­irritation (Figure 2B).⁶ Although the sap of the plant serves as the main culprit of Brazilian peppertree–­associated ACD, it appears that other parts of the plant, including the fruit, can cause irritating effects to skin on contact.^11,12 The leaves, trunk, and fruit can be harmful to both humans and animals.⁶ Chemicals from flowers and crushed fruit also can lead to irritating effects in the respiratory tract if aspirated.¹³

Urushiol, an oily resin present in most plants of the Anacardiaceae family,¹⁴ contains many chemicals, including allergenic phenols, catechols, and resorcinols.¹⁵ Urushiol-allergic individuals develop dermatitis upon exposure to Brazilian peppertree sap.⁶ Alkenyl phenols found in Brazilian peppertree lead to the cutaneous manifestations in sensitized patients.^11,12 In 1983, Stahl et al¹¹ identified a phenol, cardanol (chemical name ­3-pentadecylphenol¹⁶) C15:1, in Brazilian peppertree fruit. The group further tested this compound’s effect on skin via patch testing, which showed an allergic response.¹¹ Cashew nut shells (Anacardium occidentale) contain cardanol, anacardic acid (a phenolic acid), and cardol (a phenol with the chemical name ­5-pentadecylresorcinol),^15,16 though Stahl et al¹¹ were unable to extract these 2 substances (if present) from Brazilian peppertree fruit. When exposed to cardol and anacardic acid, those allergic to poison ivy often develop ACD,¹⁵ and these 2 substances are more irritating than cardanol.¹¹ A later study did identify cardol in addition to cardanol in Brazilian peppertree.¹²

Cutaneous Manifestations

Brazilian peppertree–induced ACD appears similar to other plant-induced ACD with linear streaks of erythema, juicy papules, vesicles, coalescing erythematous plaques, and/or occasional edema and bullae accompanied by intense pruritus.

Treatment

Avoiding contact with Brazilian peppertree is the first line of defense, and treatment for a reaction associated with exposure is similar to that of poison ivy.¹⁷ Application of cool compresses, calamine lotion, and topical astringents offer symptom alleviation, and topical steroids (eg, clobetasol propionate 0.05% twice daily) can improve mild localized ACD when given prior to formation of blisters. For more severe and diffuse ACD, oral steroids (eg, prednisone 1 mg/kg/d tapered over 2–3 weeks) likely are necessary, though intramuscular options greatly alleviate discomfort in more severe cases (eg, intramuscular triamcinolone acetonide 1 mg/kg combined with betamethasone 0.1 mg/kg). Physicians should monitor sites for any signs of superimposed bacterial infection and initiate antibiotics as necessary.¹⁷

Brazilian peppertree (Schinus terebinthifolia), a member of the Anacardiaceae family, is an internationally invasive plant that causes allergic contact dermatitis (ACD) in susceptible individuals. This noxious weed has settled into the landscape of the southern United States and continues to expand. Its key identifying features include its year-round white flowers as well as a peppery and turpentinelike aroma created by cracking its bright red berries. The ACD associated with contact—primarily with the plant’s sap—stems from known alkenyl phenols, cardol and cardanol. Treatment of Brazilian peppertree–associated ACD parallels that for poison ivy. As this pest increases its range, dermatologists living in endemic areas should familiarize themselves with Brazilian peppertree and its potential for harm.

Brazilian Peppertree Morphology and Geography

Plants in the Anacardiaceae family contribute to more ACD than any other family, and its 80 genera include most of the urushiol-containing plants, such as Toxicodendron (poison ivy, poison oak, poison sumac, Japanese lacquer tree), Anacardium (cashew tree), Mangifera (mango fruit), Semecarpus (India marking nut tree), and Schinus (Brazilian peppertree). Deciduous and evergreen tree members of the Anacardiaceae family grow primarily in tropical and subtropical locations and produce thick resins, 5-petalled flowers, and small fruit known as drupes. The genus name for Brazilian peppertree, Schinus, derives from Latin and Greek words meaning “mastic tree,” a relative of the pistachio tree that the Brazilian peppertree resembles.¹ Brazilian peppertree leaves look and smell similar to Pistacia terebinthus (turpentine tree or terebinth), from which the species name terebinthifolia derives.²

Brazilian peppertree originated in South America, particularly Brazil, Paraguay, and Argentina.³ Since the 1840s,⁴ it has been an invasive weed in the United States, notably in Florida, California, Hawaii, Alabama, Georgia,⁵ Arizona,⁶ Nevada,³ and Texas.^5,7 The plant also grows throughout the world, including parts of Africa, Asia, Central America, Europe,⁶ New Zealand,⁸ Australia, and various islands.⁹ The plant expertly outcompetes neighboring plants and has prompted control and eradication efforts in many locations.³

Identifying Features and Allergenic Plant Parts

Brazilian peppertree can be either a shrub or tree up to 30 feet tall.⁴ As an evergreen, it retains its leaves year-round. During fruiting seasons (primarily December through March⁷), bright red or pink (depending on the variety³) berries appear (Figure 1A) and contribute to its nickname “Florida holly.” Although generally considered an unwelcome guest in Florida, it does display white flowers (Figure 1B) year-round, especially from September to November.⁹ It characteristically exhibits 3 to 13 leaflets per leaf.¹⁰ The leaflets’ ovoid and ridged edges, netlike vasculature, shiny hue, and aroma can help identify the plant (Figure 2A). For decades, the sap of the Brazilian peppertree has been associated with skin ­irritation (Figure 2B).⁶ Although the sap of the plant serves as the main culprit of Brazilian peppertree–­associated ACD, it appears that other parts of the plant, including the fruit, can cause irritating effects to skin on contact.^11,12 The leaves, trunk, and fruit can be harmful to both humans and animals.⁶ Chemicals from flowers and crushed fruit also can lead to irritating effects in the respiratory tract if aspirated.¹³

Urushiol, an oily resin present in most plants of the Anacardiaceae family,¹⁴ contains many chemicals, including allergenic phenols, catechols, and resorcinols.¹⁵ Urushiol-allergic individuals develop dermatitis upon exposure to Brazilian peppertree sap.⁶ Alkenyl phenols found in Brazilian peppertree lead to the cutaneous manifestations in sensitized patients.^11,12 In 1983, Stahl et al¹¹ identified a phenol, cardanol (chemical name ­3-pentadecylphenol¹⁶) C15:1, in Brazilian peppertree fruit. The group further tested this compound’s effect on skin via patch testing, which showed an allergic response.¹¹ Cashew nut shells (Anacardium occidentale) contain cardanol, anacardic acid (a phenolic acid), and cardol (a phenol with the chemical name ­5-pentadecylresorcinol),^15,16 though Stahl et al¹¹ were unable to extract these 2 substances (if present) from Brazilian peppertree fruit. When exposed to cardol and anacardic acid, those allergic to poison ivy often develop ACD,¹⁵ and these 2 substances are more irritating than cardanol.¹¹ A later study did identify cardol in addition to cardanol in Brazilian peppertree.¹²

Cutaneous Manifestations

Brazilian peppertree–induced ACD appears similar to other plant-induced ACD with linear streaks of erythema, juicy papules, vesicles, coalescing erythematous plaques, and/or occasional edema and bullae accompanied by intense pruritus.

Treatment

Avoiding contact with Brazilian peppertree is the first line of defense, and treatment for a reaction associated with exposure is similar to that of poison ivy.¹⁷ Application of cool compresses, calamine lotion, and topical astringents offer symptom alleviation, and topical steroids (eg, clobetasol propionate 0.05% twice daily) can improve mild localized ACD when given prior to formation of blisters. For more severe and diffuse ACD, oral steroids (eg, prednisone 1 mg/kg/d tapered over 2–3 weeks) likely are necessary, though intramuscular options greatly alleviate discomfort in more severe cases (eg, intramuscular triamcinolone acetonide 1 mg/kg combined with betamethasone 0.1 mg/kg). Physicians should monitor sites for any signs of superimposed bacterial infection and initiate antibiotics as necessary.¹⁷

TOPLINE:

Pigments in permanent makeup inks include those that have been reported to cause allergic contact dermatitis (ACD), but the ability to identify these allergies in patients is limited.

METHODOLOGY:

• While the allergenic potential of pigments in traditional tattoos has been documented, there is less clarity about pigments used in inks contained in cosmetic tattoos, also known as permanent makeup, and their association with ACD.
• Researchers conducted an Internet search and identified 974 individual permanent makeup ink products sold in the United States and also identified 79 unique pigments in those products.
• They evaluated the safety data sheets of these products and performed a PubMed search to identify documented ACD cases related to these pigments.

TAKEAWAY:

• Of the 79 pigments, 20 contained inorganic metals, which included iron, aluminum, silicone, chromium, copper, titanium, molybdenum, and manganese.
• Organic pigments were more common: 59 of the remaining pigments were organic compounds, mostly azo, quinacridone, or anthraquinone dyes, including 4 black pigments made from carbon only.
• A literature search identified 29 cases where patients had developed ACD thought to be caused by at least one of the 79 pigments identified by the authors of the current study and included 10 of the 79 pigments (12%).
• In 18 of the 29 cases in the literature, patch testing to the suspected pigment had been performed; in 3 cases, ACD was suspected without confirmatory testing.

IN PRACTICE:

Permanent makeup is becoming more popular, and there have been reports of ACD related to pigments contained in the inks, the authors wrote. “Traditional patch testing methods may not be useful in confirming the presence of a pigment allergy, even if one is suspect,” they added. “Consumers and patch testing physicians would benefit from better labeling of tattoo inks and the development of protocols designed to specifically test for tattoo pigment allergies.”

SOURCE:

The study was led by Sarah Rigali, MS, of Rosalind Franklin University, Chicago Medical School, Chicago, and coauthors from the Department of Dermatology, Northwestern University, Chicago, published online in the Journal of the American Academy of Dermatology.

LIMITATIONS:

The study is limited by incomplete safety data sheets. So, many brands of permanent makeup ink could not be investigated. In addition, some pigments may not be fully disclosed in ingredient lists and precise ink content measurements were not available.

DISCLOSURES:

The study reported receiving no funding. The authors declared no conflicts of interest.

A version of this article appeared on Medscape.com.

TOPLINE:

Pigments in permanent makeup inks include those that have been reported to cause allergic contact dermatitis (ACD), but the ability to identify these allergies in patients is limited.

METHODOLOGY:

• While the allergenic potential of pigments in traditional tattoos has been documented, there is less clarity about pigments used in inks contained in cosmetic tattoos, also known as permanent makeup, and their association with ACD.
• Researchers conducted an Internet search and identified 974 individual permanent makeup ink products sold in the United States and also identified 79 unique pigments in those products.
• They evaluated the safety data sheets of these products and performed a PubMed search to identify documented ACD cases related to these pigments.

TAKEAWAY:

• Of the 79 pigments, 20 contained inorganic metals, which included iron, aluminum, silicone, chromium, copper, titanium, molybdenum, and manganese.
• Organic pigments were more common: 59 of the remaining pigments were organic compounds, mostly azo, quinacridone, or anthraquinone dyes, including 4 black pigments made from carbon only.
• A literature search identified 29 cases where patients had developed ACD thought to be caused by at least one of the 79 pigments identified by the authors of the current study and included 10 of the 79 pigments (12%).
• In 18 of the 29 cases in the literature, patch testing to the suspected pigment had been performed; in 3 cases, ACD was suspected without confirmatory testing.

IN PRACTICE:

Permanent makeup is becoming more popular, and there have been reports of ACD related to pigments contained in the inks, the authors wrote. “Traditional patch testing methods may not be useful in confirming the presence of a pigment allergy, even if one is suspect,” they added. “Consumers and patch testing physicians would benefit from better labeling of tattoo inks and the development of protocols designed to specifically test for tattoo pigment allergies.”

SOURCE:

The study was led by Sarah Rigali, MS, of Rosalind Franklin University, Chicago Medical School, Chicago, and coauthors from the Department of Dermatology, Northwestern University, Chicago, published online in the Journal of the American Academy of Dermatology.

LIMITATIONS:

The study is limited by incomplete safety data sheets. So, many brands of permanent makeup ink could not be investigated. In addition, some pigments may not be fully disclosed in ingredient lists and precise ink content measurements were not available.

DISCLOSURES:

The study reported receiving no funding. The authors declared no conflicts of interest.

A version of this article appeared on Medscape.com.

TOPLINE:

Pigments in permanent makeup inks include those that have been reported to cause allergic contact dermatitis (ACD), but the ability to identify these allergies in patients is limited.

METHODOLOGY:

• While the allergenic potential of pigments in traditional tattoos has been documented, there is less clarity about pigments used in inks contained in cosmetic tattoos, also known as permanent makeup, and their association with ACD.
• Researchers conducted an Internet search and identified 974 individual permanent makeup ink products sold in the United States and also identified 79 unique pigments in those products.
• They evaluated the safety data sheets of these products and performed a PubMed search to identify documented ACD cases related to these pigments.

TAKEAWAY:

• Of the 79 pigments, 20 contained inorganic metals, which included iron, aluminum, silicone, chromium, copper, titanium, molybdenum, and manganese.
• Organic pigments were more common: 59 of the remaining pigments were organic compounds, mostly azo, quinacridone, or anthraquinone dyes, including 4 black pigments made from carbon only.
• A literature search identified 29 cases where patients had developed ACD thought to be caused by at least one of the 79 pigments identified by the authors of the current study and included 10 of the 79 pigments (12%).
• In 18 of the 29 cases in the literature, patch testing to the suspected pigment had been performed; in 3 cases, ACD was suspected without confirmatory testing.

IN PRACTICE:

Permanent makeup is becoming more popular, and there have been reports of ACD related to pigments contained in the inks, the authors wrote. “Traditional patch testing methods may not be useful in confirming the presence of a pigment allergy, even if one is suspect,” they added. “Consumers and patch testing physicians would benefit from better labeling of tattoo inks and the development of protocols designed to specifically test for tattoo pigment allergies.”

SOURCE:

The study was led by Sarah Rigali, MS, of Rosalind Franklin University, Chicago Medical School, Chicago, and coauthors from the Department of Dermatology, Northwestern University, Chicago, published online in the Journal of the American Academy of Dermatology.

LIMITATIONS:

The study is limited by incomplete safety data sheets. So, many brands of permanent makeup ink could not be investigated. In addition, some pigments may not be fully disclosed in ingredient lists and precise ink content measurements were not available.

DISCLOSURES:

The study reported receiving no funding. The authors declared no conflicts of interest.

A version of this article appeared on Medscape.com.

The filamentous cyanobacterium Lyngbya majuscula causes irritant contact dermatitis in beachgoers, fishers, and divers in tropical and subtropical marine environments worldwide.¹ If fragments of L majuscula lodge in swimmers’ bathing suits, the toxins can become trapped against the skin and cause seaweed dermatitis.² With climate change resulting in warmer oceans and more extreme storms, L majuscula blooms likely will become more frequent and widespread, thereby increasing the risk for human exposure.^3,4 Herein, we describe the irritants that lead to dermatitis, clinical presentation, and prevention and management of seaweed dermatitis.

Identifying Features and Distribution of Plant

Lyngbya majuscula belongs to the family Oscillatoriaceae; these cyanobacteria grow as filaments and exhibit slow oscillating movements. Commonly referred to as blanketweed or mermaid’s hair due to its appearance, L majuscula grows fine hairlike clumps resembling a mass of olive-colored matted hair.¹ Its thin filaments are 10- to 30-cm long and vary in color from red to white to brown.⁵ Microscopically, a rouleauxlike arrangement of discs provides the structure of each filament.⁶

First identified in Hawaii in 1912, L majuscula was not associated with seaweed dermatitis or dermatotoxicity by the medical community until the first outbreak occurred in Oahu in 1958, though fishermen and beachgoers previously had recognized a relationship between this particular seaweed and skin irritation.^5,7 The first reporting included 125 confirmed cases, with many more mild unreported cases suspected.⁶ Now reported in about 100 locations worldwide, seaweed dermatitis outbreaks have occurred in Australia; Okinawa, Japan; Florida; and the Hawaiian and Marshall islands.^1,2

Exposure to Seaweed

Lyngbya majuscula produces more than 70 biologically active compounds that irritate the skin, eyes, and respiratory system.^2,8 It grows in marine and estuarine environments attached to seagrass, sand, and bedrock at depths of up to 30 m. Warm waters and maximal sunlight provide optimal growth conditions for L majuscula; therefore, the greatest risk for exposure occurs in the Northern and Southern hemispheres in the 1- to 2-month period following their summer solstices.⁵ Runoff during heavy rainfall, which is rich in soil extracts such as phosphorous, iron, and organic carbon, stimulates L majuscula growth and contributes to increased algal blooms.⁴

Dermatitis and Irritants

The dermatoxins Lyngbyatoxin A (LA) and debromoaplysiatoxin (DAT) cause the inflammatory and necrotic appearance of seaweed dermatitis.^1,2,5,8 Lyngbyatoxin A is an indole alkaloid that is closely related to telocidin B, a poisonous compound associated with Streptomyces bacteria.⁹ Sampling of L majuscula and extraction of the dermatoxin, along with human and animal studies, confirmed DAT irritates the skin and induces dermatitis.^5,6Stylocheilus longicauda (sea hare) feeds on L majuscula and contains isolates of DAT in its digestive tract.

Samples of L majuscula taken from several Hawaiian Islands where seaweed dermatitis outbreaks have occurred were examined for differences in toxicities via 6-hour patch tests on human skin.⁶ The samples obtained from the windward side of Oahu contained DAT and aplysiatoxin, while those obtained from the leeward side and Kahala Beach primarily contained LA. Although DAT and LA are vastly different in their molecular structures, testing elicited the same biologic response and induced the same level of skin irritation.⁶ Interestingly, not all strands of L majuscula produced LA and DAT and caused seaweed dermatitis; those that did lead to irritation were more red in color than nontoxic blooms.^5,9

Cutaneous Manifestations

Seaweed dermatitis resembles chemical and thermal burns, ranging from a mild skin rash to severe contact dermatitis with itchy, swollen, ulcerated lesions.^1,7 Patients typically develop a burning or itching sensation beneath their bathing suit or wetsuit that progresses to an erythematous papulovesicular eruption 2 to 24 hours after exposure.^2,6 Within a week, vesicles and bullae desquamate, leaving behind tender erosions.^1,2,6,8 Inframammary lesions are common in females and scrotal swelling in males.^1,6 There is no known association between length of time spent in the water and severity of symptoms.⁵

Most reactions to L majuscula occur from exposure in the water; however, particles that become aerosolized during strong winds or storms can cause seaweed dermatitis on the face. Inhalation of L majuscula may lead to mucous membrane ulceration and pulmonary edema.^1,5,6 Noncutaneous manifestations of seaweed dermatitis include headache, fatigue, and swelling of the eyes, nose, and throat (Figures 1 and 2).^1,5

Prevention and Management

To prevent seaweed dermatitis, avoid swimming in ocean water during L majuscula blooms,¹⁰ which frequently occur following the summer solstices in the Northern and Southern hemispheres.⁵ The National Centers for Coastal Ocean Science Harmful Algae Bloom Monitoring System provides real-time access to algae bloom locations.¹¹ Although this monitoring system is not specific to L majuscula, it may be helpful in determining where potential blooms are. Wearing protective clothing such as coveralls may benefit individuals who enter the water during blooms, but it does not guarantee protection.¹⁰

Currently, there is no treatment for seaweed dermatitis, but symptom management may reduce discomfort and pain. Washing affected skin with soap and water within an hour of exposure may help reduce the severity of seaweed dermatitis, though studies have shown mixed results.^6,7 Application of cool compresses and soothing ointments (eg, calamine) provide symptomatic relief and promote healing.⁷ The dermatitis typically self-resolves within 1 week.

The filamentous cyanobacterium Lyngbya majuscula causes irritant contact dermatitis in beachgoers, fishers, and divers in tropical and subtropical marine environments worldwide.¹ If fragments of L majuscula lodge in swimmers’ bathing suits, the toxins can become trapped against the skin and cause seaweed dermatitis.² With climate change resulting in warmer oceans and more extreme storms, L majuscula blooms likely will become more frequent and widespread, thereby increasing the risk for human exposure.^3,4 Herein, we describe the irritants that lead to dermatitis, clinical presentation, and prevention and management of seaweed dermatitis.

Identifying Features and Distribution of Plant

Lyngbya majuscula belongs to the family Oscillatoriaceae; these cyanobacteria grow as filaments and exhibit slow oscillating movements. Commonly referred to as blanketweed or mermaid’s hair due to its appearance, L majuscula grows fine hairlike clumps resembling a mass of olive-colored matted hair.¹ Its thin filaments are 10- to 30-cm long and vary in color from red to white to brown.⁵ Microscopically, a rouleauxlike arrangement of discs provides the structure of each filament.⁶

First identified in Hawaii in 1912, L majuscula was not associated with seaweed dermatitis or dermatotoxicity by the medical community until the first outbreak occurred in Oahu in 1958, though fishermen and beachgoers previously had recognized a relationship between this particular seaweed and skin irritation.^5,7 The first reporting included 125 confirmed cases, with many more mild unreported cases suspected.⁶ Now reported in about 100 locations worldwide, seaweed dermatitis outbreaks have occurred in Australia; Okinawa, Japan; Florida; and the Hawaiian and Marshall islands.^1,2

Exposure to Seaweed

Lyngbya majuscula produces more than 70 biologically active compounds that irritate the skin, eyes, and respiratory system.^2,8 It grows in marine and estuarine environments attached to seagrass, sand, and bedrock at depths of up to 30 m. Warm waters and maximal sunlight provide optimal growth conditions for L majuscula; therefore, the greatest risk for exposure occurs in the Northern and Southern hemispheres in the 1- to 2-month period following their summer solstices.⁵ Runoff during heavy rainfall, which is rich in soil extracts such as phosphorous, iron, and organic carbon, stimulates L majuscula growth and contributes to increased algal blooms.⁴

Dermatitis and Irritants

The dermatoxins Lyngbyatoxin A (LA) and debromoaplysiatoxin (DAT) cause the inflammatory and necrotic appearance of seaweed dermatitis.^1,2,5,8 Lyngbyatoxin A is an indole alkaloid that is closely related to telocidin B, a poisonous compound associated with Streptomyces bacteria.⁹ Sampling of L majuscula and extraction of the dermatoxin, along with human and animal studies, confirmed DAT irritates the skin and induces dermatitis.^5,6Stylocheilus longicauda (sea hare) feeds on L majuscula and contains isolates of DAT in its digestive tract.

Samples of L majuscula taken from several Hawaiian Islands where seaweed dermatitis outbreaks have occurred were examined for differences in toxicities via 6-hour patch tests on human skin.⁶ The samples obtained from the windward side of Oahu contained DAT and aplysiatoxin, while those obtained from the leeward side and Kahala Beach primarily contained LA. Although DAT and LA are vastly different in their molecular structures, testing elicited the same biologic response and induced the same level of skin irritation.⁶ Interestingly, not all strands of L majuscula produced LA and DAT and caused seaweed dermatitis; those that did lead to irritation were more red in color than nontoxic blooms.^5,9

Cutaneous Manifestations

Seaweed dermatitis resembles chemical and thermal burns, ranging from a mild skin rash to severe contact dermatitis with itchy, swollen, ulcerated lesions.^1,7 Patients typically develop a burning or itching sensation beneath their bathing suit or wetsuit that progresses to an erythematous papulovesicular eruption 2 to 24 hours after exposure.^2,6 Within a week, vesicles and bullae desquamate, leaving behind tender erosions.^1,2,6,8 Inframammary lesions are common in females and scrotal swelling in males.^1,6 There is no known association between length of time spent in the water and severity of symptoms.⁵

Most reactions to L majuscula occur from exposure in the water; however, particles that become aerosolized during strong winds or storms can cause seaweed dermatitis on the face. Inhalation of L majuscula may lead to mucous membrane ulceration and pulmonary edema.^1,5,6 Noncutaneous manifestations of seaweed dermatitis include headache, fatigue, and swelling of the eyes, nose, and throat (Figures 1 and 2).^1,5

Prevention and Management

To prevent seaweed dermatitis, avoid swimming in ocean water during L majuscula blooms,¹⁰ which frequently occur following the summer solstices in the Northern and Southern hemispheres.⁵ The National Centers for Coastal Ocean Science Harmful Algae Bloom Monitoring System provides real-time access to algae bloom locations.¹¹ Although this monitoring system is not specific to L majuscula, it may be helpful in determining where potential blooms are. Wearing protective clothing such as coveralls may benefit individuals who enter the water during blooms, but it does not guarantee protection.¹⁰

Currently, there is no treatment for seaweed dermatitis, but symptom management may reduce discomfort and pain. Washing affected skin with soap and water within an hour of exposure may help reduce the severity of seaweed dermatitis, though studies have shown mixed results.^6,7 Application of cool compresses and soothing ointments (eg, calamine) provide symptomatic relief and promote healing.⁷ The dermatitis typically self-resolves within 1 week.

The filamentous cyanobacterium Lyngbya majuscula causes irritant contact dermatitis in beachgoers, fishers, and divers in tropical and subtropical marine environments worldwide.¹ If fragments of L majuscula lodge in swimmers’ bathing suits, the toxins can become trapped against the skin and cause seaweed dermatitis.² With climate change resulting in warmer oceans and more extreme storms, L majuscula blooms likely will become more frequent and widespread, thereby increasing the risk for human exposure.^3,4 Herein, we describe the irritants that lead to dermatitis, clinical presentation, and prevention and management of seaweed dermatitis.

Identifying Features and Distribution of Plant

Lyngbya majuscula belongs to the family Oscillatoriaceae; these cyanobacteria grow as filaments and exhibit slow oscillating movements. Commonly referred to as blanketweed or mermaid’s hair due to its appearance, L majuscula grows fine hairlike clumps resembling a mass of olive-colored matted hair.¹ Its thin filaments are 10- to 30-cm long and vary in color from red to white to brown.⁵ Microscopically, a rouleauxlike arrangement of discs provides the structure of each filament.⁶

First identified in Hawaii in 1912, L majuscula was not associated with seaweed dermatitis or dermatotoxicity by the medical community until the first outbreak occurred in Oahu in 1958, though fishermen and beachgoers previously had recognized a relationship between this particular seaweed and skin irritation.^5,7 The first reporting included 125 confirmed cases, with many more mild unreported cases suspected.⁶ Now reported in about 100 locations worldwide, seaweed dermatitis outbreaks have occurred in Australia; Okinawa, Japan; Florida; and the Hawaiian and Marshall islands.^1,2

Exposure to Seaweed

Lyngbya majuscula produces more than 70 biologically active compounds that irritate the skin, eyes, and respiratory system.^2,8 It grows in marine and estuarine environments attached to seagrass, sand, and bedrock at depths of up to 30 m. Warm waters and maximal sunlight provide optimal growth conditions for L majuscula; therefore, the greatest risk for exposure occurs in the Northern and Southern hemispheres in the 1- to 2-month period following their summer solstices.⁵ Runoff during heavy rainfall, which is rich in soil extracts such as phosphorous, iron, and organic carbon, stimulates L majuscula growth and contributes to increased algal blooms.⁴

Dermatitis and Irritants

The dermatoxins Lyngbyatoxin A (LA) and debromoaplysiatoxin (DAT) cause the inflammatory and necrotic appearance of seaweed dermatitis.^1,2,5,8 Lyngbyatoxin A is an indole alkaloid that is closely related to telocidin B, a poisonous compound associated with Streptomyces bacteria.⁹ Sampling of L majuscula and extraction of the dermatoxin, along with human and animal studies, confirmed DAT irritates the skin and induces dermatitis.^5,6Stylocheilus longicauda (sea hare) feeds on L majuscula and contains isolates of DAT in its digestive tract.

Samples of L majuscula taken from several Hawaiian Islands where seaweed dermatitis outbreaks have occurred were examined for differences in toxicities via 6-hour patch tests on human skin.⁶ The samples obtained from the windward side of Oahu contained DAT and aplysiatoxin, while those obtained from the leeward side and Kahala Beach primarily contained LA. Although DAT and LA are vastly different in their molecular structures, testing elicited the same biologic response and induced the same level of skin irritation.⁶ Interestingly, not all strands of L majuscula produced LA and DAT and caused seaweed dermatitis; those that did lead to irritation were more red in color than nontoxic blooms.^5,9

Cutaneous Manifestations

Seaweed dermatitis resembles chemical and thermal burns, ranging from a mild skin rash to severe contact dermatitis with itchy, swollen, ulcerated lesions.^1,7 Patients typically develop a burning or itching sensation beneath their bathing suit or wetsuit that progresses to an erythematous papulovesicular eruption 2 to 24 hours after exposure.^2,6 Within a week, vesicles and bullae desquamate, leaving behind tender erosions.^1,2,6,8 Inframammary lesions are common in females and scrotal swelling in males.^1,6 There is no known association between length of time spent in the water and severity of symptoms.⁵

Most reactions to L majuscula occur from exposure in the water; however, particles that become aerosolized during strong winds or storms can cause seaweed dermatitis on the face. Inhalation of L majuscula may lead to mucous membrane ulceration and pulmonary edema.^1,5,6 Noncutaneous manifestations of seaweed dermatitis include headache, fatigue, and swelling of the eyes, nose, and throat (Figures 1 and 2).^1,5

Prevention and Management

To prevent seaweed dermatitis, avoid swimming in ocean water during L majuscula blooms,¹⁰ which frequently occur following the summer solstices in the Northern and Southern hemispheres.⁵ The National Centers for Coastal Ocean Science Harmful Algae Bloom Monitoring System provides real-time access to algae bloom locations.¹¹ Although this monitoring system is not specific to L majuscula, it may be helpful in determining where potential blooms are. Wearing protective clothing such as coveralls may benefit individuals who enter the water during blooms, but it does not guarantee protection.¹⁰

Currently, there is no treatment for seaweed dermatitis, but symptom management may reduce discomfort and pain. Washing affected skin with soap and water within an hour of exposure may help reduce the severity of seaweed dermatitis, though studies have shown mixed results.^6,7 Application of cool compresses and soothing ointments (eg, calamine) provide symptomatic relief and promote healing.⁷ The dermatitis typically self-resolves within 1 week.

To the Editor:

Langerhans cell histiocytosis (LCH) is a rare inflammatory neoplasia caused by accumulation of clonal Langerhans cells in 1 or more organs. The clinical spectrum is diverse, ranging from mild, single-organ involvement that may resolve spontaneously to severe progressive multisystem disease that can be fatal. It is most prevalent in children, affecting an estimated 4 to 5 children for every 1 million annually, with male predominance.¹ The pathogenesis is driven by activating mutations in the mitogen-activated protein kinase pathway, with the BRAF V600E mutation detected in most LCH patients, resulting in proliferation of pathologic Langerhans cells and dysregulated expression of inflammatory cytokines in LCH lesions.² A biopsy of lesional tissue is required for definitive diagnosis. Histopathology reveals a mixed inflammatory infiltrate and characteristic mononuclear cells with reniform nuclei that are positive for CD1a and CD207 proteins on immunohistochemical staining.³

Langerhans cell histiocytosis is categorized by the extent of organ involvement. It commonly affects the bones, skin, pituitary gland, liver, lungs, bone marrow, and lymph nodes.⁴ Single-system LCH involves a single organ with unifocal or multifocal lesions; multisystem LCH involves 2 or more organs and has a worse prognosis if risk organs (eg, liver, spleen, bone marrow) are involved.⁴

Skin lesions are reported in more than half of LCH cases and are the most common initial manifestation in patients younger than 2 years.⁴ Cutaneous findings are highly variable, which poses a diagnostic challenge. Common morphologies include erythematous papules, pustules, papulovesicles, scaly plaques, erosions, and petechiae. Lesions can be solitary or widespread and favor the trunk, head, and face.⁴ We describe an atypical case of hypopigmented cutaneous LCH and review the literature on this morphology in patients with skin of color.

A 7-month-old Hispanic male infant who was otherwise healthy presented with numerous hypopigmented macules and pink papules on the trunk and groin that had progressed since birth. A review of systems was unremarkable. Physical examination revealed 1- to 3-mm, discrete, hypopigmented macules intermixed with 1- to 2-mm pearly pink papules scattered on the back, chest, abdomen, and inguinal folds (Figure 1). Some lesions appeared koebnerized; however, the parents denied a history of scratching or trauma.

Histopathology of a lesion in the inguinal fold showed aggregates of mononuclear cells with reniform nuclei and abundant amphophilic cytoplasm in the papillary dermis, with focal extension into the epidermis. Scattered eosinophils and multinucleated giant cells were present in the dermal inflammatory infiltrate (Figure 2). Immunohistochemical staining was positive for CD1a (Figure 3) and S-100 protein (Figure 4). Although epidermal Langerhans cell collections also can be seen in allergic contact dermatitis,⁵ predominant involvement of the papillary dermis and the presence of multinucleated giant cells are characteristic of LCH.⁴ Given these findings, which were consistent with LCH, the dermatopathology deemed BRAF V600E immunostaining unnecessary for diagnostic purposes.

The patient was referred to the hematology and oncology department to undergo thorough evaluation for extracutaneous involvement. The workup included a complete blood cell count, liver function testing, electrolyte assessment, skeletal survey, chest radiography, and ultrasonography of the liver and spleen. All results were negative, suggesting a diagnosis of single-system cutaneous LCH.

Three months later, the patient presented to dermatology with spontaneous regression of all skin lesions. Continued follow-up—every 6 months for 5 years—was recommended to monitor for disease recurrence or progression to multisystem disease.

Cutaneous LCH is a clinically heterogeneous disease with the potential for multisystem involvement and long-term sequelae; therefore, timely diagnosis is paramount to optimize outcomes. However, delayed diagnosis is common because of the spectrum of skin findings that can mimic common pediatric dermatoses, such as seborrheic dermatitis, atopic dermatitis, and diaper dermatitis.⁴ In one study, the median time from onset of skin lesions to diagnostic biopsy was longer than 3 months (maximum, 5 years).⁶ Our patient was referred to dermatology 7 months after onset of hypopigmented macules, a rarely reported cutaneous manifestation of LCH.

A PubMed search of articles indexed for MEDLINE from 1994 to 2019 using the terms Langerhans cell histiocytotis and hypopigmented yielded 17 cases of LCH presenting as hypopigmented skin lesions (Table).^7-22 All cases occurred in patients with skin of color (ie, patients of Asian, Hispanic, or African descent). Hypopigmented macules were the only cutaneous manifestation in 10 (59%) cases. Lesions most commonly were distributed on the trunk (16/17 [94%]) and extremities (8/17 [47%]). The median age of onset was 1 month; 76% (13/17) of patients developed skin lesions before 1 year of age, indicating that this morphology may be more common in newborns. In most patients, the diagnosis was single-system cutaneous LCH; they exhibited spontaneous regression by 8 months of age on average, suggesting that this variant may be associated with a better prognosis. Mori and colleagues²¹ hypothesized that hypopigmented lesions may represent the resolving stage of active LCH based on histopathologic findings of dermal pallor and fibrosis in a hypopigmented LCH lesion. However, systemic involvement was reported in 7 cases of hypopigmented LCH, highlighting the importance of assessing for multisystem disease regardless of cutaneous morphology.²¹Langerhans cell histiocytosis should be considered in the differential diagnosis when evaluating hypopigmented skin eruptions in infants with darker skin types. Prompt diagnosis of this atypical variant requires a higher index of suspicion because of its rarity and the polymorphic nature of cutaneous LCH. This morphology may go undiagnosed in the setting of mild or spontaneously resolving disease; notwithstanding, accurate diagnosis and longitudinal surveillance are necessary given the potential for progressive systemic involvement.

To the Editor:

Langerhans cell histiocytosis (LCH) is a rare inflammatory neoplasia caused by accumulation of clonal Langerhans cells in 1 or more organs. The clinical spectrum is diverse, ranging from mild, single-organ involvement that may resolve spontaneously to severe progressive multisystem disease that can be fatal. It is most prevalent in children, affecting an estimated 4 to 5 children for every 1 million annually, with male predominance.¹ The pathogenesis is driven by activating mutations in the mitogen-activated protein kinase pathway, with the BRAF V600E mutation detected in most LCH patients, resulting in proliferation of pathologic Langerhans cells and dysregulated expression of inflammatory cytokines in LCH lesions.² A biopsy of lesional tissue is required for definitive diagnosis. Histopathology reveals a mixed inflammatory infiltrate and characteristic mononuclear cells with reniform nuclei that are positive for CD1a and CD207 proteins on immunohistochemical staining.³

Langerhans cell histiocytosis is categorized by the extent of organ involvement. It commonly affects the bones, skin, pituitary gland, liver, lungs, bone marrow, and lymph nodes.⁴ Single-system LCH involves a single organ with unifocal or multifocal lesions; multisystem LCH involves 2 or more organs and has a worse prognosis if risk organs (eg, liver, spleen, bone marrow) are involved.⁴

Skin lesions are reported in more than half of LCH cases and are the most common initial manifestation in patients younger than 2 years.⁴ Cutaneous findings are highly variable, which poses a diagnostic challenge. Common morphologies include erythematous papules, pustules, papulovesicles, scaly plaques, erosions, and petechiae. Lesions can be solitary or widespread and favor the trunk, head, and face.⁴ We describe an atypical case of hypopigmented cutaneous LCH and review the literature on this morphology in patients with skin of color.

A 7-month-old Hispanic male infant who was otherwise healthy presented with numerous hypopigmented macules and pink papules on the trunk and groin that had progressed since birth. A review of systems was unremarkable. Physical examination revealed 1- to 3-mm, discrete, hypopigmented macules intermixed with 1- to 2-mm pearly pink papules scattered on the back, chest, abdomen, and inguinal folds (Figure 1). Some lesions appeared koebnerized; however, the parents denied a history of scratching or trauma.

Histopathology of a lesion in the inguinal fold showed aggregates of mononuclear cells with reniform nuclei and abundant amphophilic cytoplasm in the papillary dermis, with focal extension into the epidermis. Scattered eosinophils and multinucleated giant cells were present in the dermal inflammatory infiltrate (Figure 2). Immunohistochemical staining was positive for CD1a (Figure 3) and S-100 protein (Figure 4). Although epidermal Langerhans cell collections also can be seen in allergic contact dermatitis,⁵ predominant involvement of the papillary dermis and the presence of multinucleated giant cells are characteristic of LCH.⁴ Given these findings, which were consistent with LCH, the dermatopathology deemed BRAF V600E immunostaining unnecessary for diagnostic purposes.

The patient was referred to the hematology and oncology department to undergo thorough evaluation for extracutaneous involvement. The workup included a complete blood cell count, liver function testing, electrolyte assessment, skeletal survey, chest radiography, and ultrasonography of the liver and spleen. All results were negative, suggesting a diagnosis of single-system cutaneous LCH.

Three months later, the patient presented to dermatology with spontaneous regression of all skin lesions. Continued follow-up—every 6 months for 5 years—was recommended to monitor for disease recurrence or progression to multisystem disease.

Cutaneous LCH is a clinically heterogeneous disease with the potential for multisystem involvement and long-term sequelae; therefore, timely diagnosis is paramount to optimize outcomes. However, delayed diagnosis is common because of the spectrum of skin findings that can mimic common pediatric dermatoses, such as seborrheic dermatitis, atopic dermatitis, and diaper dermatitis.⁴ In one study, the median time from onset of skin lesions to diagnostic biopsy was longer than 3 months (maximum, 5 years).⁶ Our patient was referred to dermatology 7 months after onset of hypopigmented macules, a rarely reported cutaneous manifestation of LCH.

A PubMed search of articles indexed for MEDLINE from 1994 to 2019 using the terms Langerhans cell histiocytotis and hypopigmented yielded 17 cases of LCH presenting as hypopigmented skin lesions (Table).^7-22 All cases occurred in patients with skin of color (ie, patients of Asian, Hispanic, or African descent). Hypopigmented macules were the only cutaneous manifestation in 10 (59%) cases. Lesions most commonly were distributed on the trunk (16/17 [94%]) and extremities (8/17 [47%]). The median age of onset was 1 month; 76% (13/17) of patients developed skin lesions before 1 year of age, indicating that this morphology may be more common in newborns. In most patients, the diagnosis was single-system cutaneous LCH; they exhibited spontaneous regression by 8 months of age on average, suggesting that this variant may be associated with a better prognosis. Mori and colleagues²¹ hypothesized that hypopigmented lesions may represent the resolving stage of active LCH based on histopathologic findings of dermal pallor and fibrosis in a hypopigmented LCH lesion. However, systemic involvement was reported in 7 cases of hypopigmented LCH, highlighting the importance of assessing for multisystem disease regardless of cutaneous morphology.²¹Langerhans cell histiocytosis should be considered in the differential diagnosis when evaluating hypopigmented skin eruptions in infants with darker skin types. Prompt diagnosis of this atypical variant requires a higher index of suspicion because of its rarity and the polymorphic nature of cutaneous LCH. This morphology may go undiagnosed in the setting of mild or spontaneously resolving disease; notwithstanding, accurate diagnosis and longitudinal surveillance are necessary given the potential for progressive systemic involvement.

To the Editor:

Langerhans cell histiocytosis (LCH) is a rare inflammatory neoplasia caused by accumulation of clonal Langerhans cells in 1 or more organs. The clinical spectrum is diverse, ranging from mild, single-organ involvement that may resolve spontaneously to severe progressive multisystem disease that can be fatal. It is most prevalent in children, affecting an estimated 4 to 5 children for every 1 million annually, with male predominance.¹ The pathogenesis is driven by activating mutations in the mitogen-activated protein kinase pathway, with the BRAF V600E mutation detected in most LCH patients, resulting in proliferation of pathologic Langerhans cells and dysregulated expression of inflammatory cytokines in LCH lesions.² A biopsy of lesional tissue is required for definitive diagnosis. Histopathology reveals a mixed inflammatory infiltrate and characteristic mononuclear cells with reniform nuclei that are positive for CD1a and CD207 proteins on immunohistochemical staining.³

Langerhans cell histiocytosis is categorized by the extent of organ involvement. It commonly affects the bones, skin, pituitary gland, liver, lungs, bone marrow, and lymph nodes.⁴ Single-system LCH involves a single organ with unifocal or multifocal lesions; multisystem LCH involves 2 or more organs and has a worse prognosis if risk organs (eg, liver, spleen, bone marrow) are involved.⁴

Skin lesions are reported in more than half of LCH cases and are the most common initial manifestation in patients younger than 2 years.⁴ Cutaneous findings are highly variable, which poses a diagnostic challenge. Common morphologies include erythematous papules, pustules, papulovesicles, scaly plaques, erosions, and petechiae. Lesions can be solitary or widespread and favor the trunk, head, and face.⁴ We describe an atypical case of hypopigmented cutaneous LCH and review the literature on this morphology in patients with skin of color.

A 7-month-old Hispanic male infant who was otherwise healthy presented with numerous hypopigmented macules and pink papules on the trunk and groin that had progressed since birth. A review of systems was unremarkable. Physical examination revealed 1- to 3-mm, discrete, hypopigmented macules intermixed with 1- to 2-mm pearly pink papules scattered on the back, chest, abdomen, and inguinal folds (Figure 1). Some lesions appeared koebnerized; however, the parents denied a history of scratching or trauma.

Histopathology of a lesion in the inguinal fold showed aggregates of mononuclear cells with reniform nuclei and abundant amphophilic cytoplasm in the papillary dermis, with focal extension into the epidermis. Scattered eosinophils and multinucleated giant cells were present in the dermal inflammatory infiltrate (Figure 2). Immunohistochemical staining was positive for CD1a (Figure 3) and S-100 protein (Figure 4). Although epidermal Langerhans cell collections also can be seen in allergic contact dermatitis,⁵ predominant involvement of the papillary dermis and the presence of multinucleated giant cells are characteristic of LCH.⁴ Given these findings, which were consistent with LCH, the dermatopathology deemed BRAF V600E immunostaining unnecessary for diagnostic purposes.

The patient was referred to the hematology and oncology department to undergo thorough evaluation for extracutaneous involvement. The workup included a complete blood cell count, liver function testing, electrolyte assessment, skeletal survey, chest radiography, and ultrasonography of the liver and spleen. All results were negative, suggesting a diagnosis of single-system cutaneous LCH.

Three months later, the patient presented to dermatology with spontaneous regression of all skin lesions. Continued follow-up—every 6 months for 5 years—was recommended to monitor for disease recurrence or progression to multisystem disease.

Cutaneous LCH is a clinically heterogeneous disease with the potential for multisystem involvement and long-term sequelae; therefore, timely diagnosis is paramount to optimize outcomes. However, delayed diagnosis is common because of the spectrum of skin findings that can mimic common pediatric dermatoses, such as seborrheic dermatitis, atopic dermatitis, and diaper dermatitis.⁴ In one study, the median time from onset of skin lesions to diagnostic biopsy was longer than 3 months (maximum, 5 years).⁶ Our patient was referred to dermatology 7 months after onset of hypopigmented macules, a rarely reported cutaneous manifestation of LCH.

A PubMed search of articles indexed for MEDLINE from 1994 to 2019 using the terms Langerhans cell histiocytotis and hypopigmented yielded 17 cases of LCH presenting as hypopigmented skin lesions (Table).^7-22 All cases occurred in patients with skin of color (ie, patients of Asian, Hispanic, or African descent). Hypopigmented macules were the only cutaneous manifestation in 10 (59%) cases. Lesions most commonly were distributed on the trunk (16/17 [94%]) and extremities (8/17 [47%]). The median age of onset was 1 month; 76% (13/17) of patients developed skin lesions before 1 year of age, indicating that this morphology may be more common in newborns. In most patients, the diagnosis was single-system cutaneous LCH; they exhibited spontaneous regression by 8 months of age on average, suggesting that this variant may be associated with a better prognosis. Mori and colleagues²¹ hypothesized that hypopigmented lesions may represent the resolving stage of active LCH based on histopathologic findings of dermal pallor and fibrosis in a hypopigmented LCH lesion. However, systemic involvement was reported in 7 cases of hypopigmented LCH, highlighting the importance of assessing for multisystem disease regardless of cutaneous morphology.²¹Langerhans cell histiocytosis should be considered in the differential diagnosis when evaluating hypopigmented skin eruptions in infants with darker skin types. Prompt diagnosis of this atypical variant requires a higher index of suspicion because of its rarity and the polymorphic nature of cutaneous LCH. This morphology may go undiagnosed in the setting of mild or spontaneously resolving disease; notwithstanding, accurate diagnosis and longitudinal surveillance are necessary given the potential for progressive systemic involvement.

To the Editor:

The term palisaded neutrophilic and granulomatous dermatitis (PNGD) has been proposed to encompass various conditions, including Winkelmann granuloma and superficial ulcerating rheumatoid necrobiosis. More recently, PNGD has been classified along with interstitial granulomatous dermatitis and interstitial granulomatous drug reaction under a unifying rubric of reactive granulomatous dermatitis (RGD).^1-4 The diagnosis of RGD can be challenging because of a range of clinical and histopathologic features as well as variable nomenclature.^1-3,5

Palisaded neutrophilic and granulomatous dermatitis classically manifests with papules and small plaques on the extensor extremities, with histopathology showing characteristic necrobiosis with both neutrophils and histiocytes.^1,2,6 We report 6 cases of RGD, including an index case in which a predominance of neutrophils in the infiltrate impeded the diagnosis.

An 85-year-old woman (the index patient) presented with a several-week history of asymmetric crusted papules on the right upper extremity—3 lesions on the elbow and forearm and 1 lesion on a finger. She was an avid gardener with severe rheumatoid arthritis treated with Janus kinase (JAK) inhibitor therapy. An initial biopsy of the elbow revealed a dense infiltrate of neutrophils and sparse eosinophils within the dermis. Special stains for bacterial, fungal, and acid-fast organisms were negative.

Because infection with sporotrichoid spread remained high in the differential diagnosis, the JAK inhibitor was discontinued and an antifungal agent was initiated. Given the persistence of the lesions, a subsequent biopsy of the right finger revealed scarce neutrophils and predominant histiocytes with rare foci of degenerated collagen. Sporotrichosis remained the leading diagnosis for these unilateral lesions. The patient subsequently developed additional crusted papules on the left arm (Figure 1). A biopsy of a left elbow lesion revealed palisades of histiocytes around degenerated collagen and collections of neutrophils compatible with RGD (Figures 2 and 3). Incidentally, the patient also presented with bilateral lower extremity palpable purpura, with a biopsy showing leukocytoclastic vasculitis. Antifungal therapy was discontinued and JAK inhibitor therapy resumed, with partial resolution of both the arm and right finger lesions and complete resolution of the lower extremity palpable purpura over several months.

The dense neutrophilic infiltrate and asymmetric presentation seen in our index patient’s initial biopsy hindered categorization of the cutaneous findings as RGD in association with her rheumatoid arthritis rather than as an infectious process. To ascertain whether diagnosis also was difficult in other cases of RGD, we conducted a search of the Yale Dermatopathology database for the diagnosis palisaded neutrophilic and granulomatous dermatitis, a term consistently used at our institution over the past decade. This study was approved by the institutional review board of Yale University (New Haven, Connecticut), and informed consent was waived. The search covered a 10-year period; 13 patients were found. Eight patients were eliminated because further clinical information or follow-up could not be obtained, leaving 5 additional cases (Table). The 8 eliminated cases were consultations submitted to the laboratory by outside pathologists from other institutions.

To the Editor:

The term palisaded neutrophilic and granulomatous dermatitis (PNGD) has been proposed to encompass various conditions, including Winkelmann granuloma and superficial ulcerating rheumatoid necrobiosis. More recently, PNGD has been classified along with interstitial granulomatous dermatitis and interstitial granulomatous drug reaction under a unifying rubric of reactive granulomatous dermatitis (RGD).^1-4 The diagnosis of RGD can be challenging because of a range of clinical and histopathologic features as well as variable nomenclature.^1-3,5

Palisaded neutrophilic and granulomatous dermatitis classically manifests with papules and small plaques on the extensor extremities, with histopathology showing characteristic necrobiosis with both neutrophils and histiocytes.^1,2,6 We report 6 cases of RGD, including an index case in which a predominance of neutrophils in the infiltrate impeded the diagnosis.

An 85-year-old woman (the index patient) presented with a several-week history of asymmetric crusted papules on the right upper extremity—3 lesions on the elbow and forearm and 1 lesion on a finger. She was an avid gardener with severe rheumatoid arthritis treated with Janus kinase (JAK) inhibitor therapy. An initial biopsy of the elbow revealed a dense infiltrate of neutrophils and sparse eosinophils within the dermis. Special stains for bacterial, fungal, and acid-fast organisms were negative.

Because infection with sporotrichoid spread remained high in the differential diagnosis, the JAK inhibitor was discontinued and an antifungal agent was initiated. Given the persistence of the lesions, a subsequent biopsy of the right finger revealed scarce neutrophils and predominant histiocytes with rare foci of degenerated collagen. Sporotrichosis remained the leading diagnosis for these unilateral lesions. The patient subsequently developed additional crusted papules on the left arm (Figure 1). A biopsy of a left elbow lesion revealed palisades of histiocytes around degenerated collagen and collections of neutrophils compatible with RGD (Figures 2 and 3). Incidentally, the patient also presented with bilateral lower extremity palpable purpura, with a biopsy showing leukocytoclastic vasculitis. Antifungal therapy was discontinued and JAK inhibitor therapy resumed, with partial resolution of both the arm and right finger lesions and complete resolution of the lower extremity palpable purpura over several months.

The dense neutrophilic infiltrate and asymmetric presentation seen in our index patient’s initial biopsy hindered categorization of the cutaneous findings as RGD in association with her rheumatoid arthritis rather than as an infectious process. To ascertain whether diagnosis also was difficult in other cases of RGD, we conducted a search of the Yale Dermatopathology database for the diagnosis palisaded neutrophilic and granulomatous dermatitis, a term consistently used at our institution over the past decade. This study was approved by the institutional review board of Yale University (New Haven, Connecticut), and informed consent was waived. The search covered a 10-year period; 13 patients were found. Eight patients were eliminated because further clinical information or follow-up could not be obtained, leaving 5 additional cases (Table). The 8 eliminated cases were consultations submitted to the laboratory by outside pathologists from other institutions.

To the Editor:

The term palisaded neutrophilic and granulomatous dermatitis (PNGD) has been proposed to encompass various conditions, including Winkelmann granuloma and superficial ulcerating rheumatoid necrobiosis. More recently, PNGD has been classified along with interstitial granulomatous dermatitis and interstitial granulomatous drug reaction under a unifying rubric of reactive granulomatous dermatitis (RGD).^1-4 The diagnosis of RGD can be challenging because of a range of clinical and histopathologic features as well as variable nomenclature.^1-3,5

Palisaded neutrophilic and granulomatous dermatitis classically manifests with papules and small plaques on the extensor extremities, with histopathology showing characteristic necrobiosis with both neutrophils and histiocytes.^1,2,6 We report 6 cases of RGD, including an index case in which a predominance of neutrophils in the infiltrate impeded the diagnosis.

An 85-year-old woman (the index patient) presented with a several-week history of asymmetric crusted papules on the right upper extremity—3 lesions on the elbow and forearm and 1 lesion on a finger. She was an avid gardener with severe rheumatoid arthritis treated with Janus kinase (JAK) inhibitor therapy. An initial biopsy of the elbow revealed a dense infiltrate of neutrophils and sparse eosinophils within the dermis. Special stains for bacterial, fungal, and acid-fast organisms were negative.

Because infection with sporotrichoid spread remained high in the differential diagnosis, the JAK inhibitor was discontinued and an antifungal agent was initiated. Given the persistence of the lesions, a subsequent biopsy of the right finger revealed scarce neutrophils and predominant histiocytes with rare foci of degenerated collagen. Sporotrichosis remained the leading diagnosis for these unilateral lesions. The patient subsequently developed additional crusted papules on the left arm (Figure 1). A biopsy of a left elbow lesion revealed palisades of histiocytes around degenerated collagen and collections of neutrophils compatible with RGD (Figures 2 and 3). Incidentally, the patient also presented with bilateral lower extremity palpable purpura, with a biopsy showing leukocytoclastic vasculitis. Antifungal therapy was discontinued and JAK inhibitor therapy resumed, with partial resolution of both the arm and right finger lesions and complete resolution of the lower extremity palpable purpura over several months.

The dense neutrophilic infiltrate and asymmetric presentation seen in our index patient’s initial biopsy hindered categorization of the cutaneous findings as RGD in association with her rheumatoid arthritis rather than as an infectious process. To ascertain whether diagnosis also was difficult in other cases of RGD, we conducted a search of the Yale Dermatopathology database for the diagnosis palisaded neutrophilic and granulomatous dermatitis, a term consistently used at our institution over the past decade. This study was approved by the institutional review board of Yale University (New Haven, Connecticut), and informed consent was waived. The search covered a 10-year period; 13 patients were found. Eight patients were eliminated because further clinical information or follow-up could not be obtained, leaving 5 additional cases (Table). The 8 eliminated cases were consultations submitted to the laboratory by outside pathologists from other institutions.

To the Editor:

A 32-year-old man presented to our clinic with acute-onset erythroderma associated with severe itching of 1 month’s duration. The patient developed the eruption after receiving the second dose of the Sinopharm BBIBP COVID-19 vaccine (BBIBP-CorV) 2 weeks prior to presentation. His medical history was unremarkable. There was no personal or family history of skin disease and no history of drug intake. Physical examination revealed orange-red erythroderma (Figure 1A) with islands of sparing,keratotic follicular orange-red papules on both legs and feet (Figure 1B), well-defined waxy palmoplantar keratoderma (Figures 1C and 1D), and fine scales on the face and scalp. The clinical and laboratory workup were normal, including a negative test for HIV infection.

Histopathology of two 4-mm punch biopsies of the skin on the trunk and lower limb showed irregular epidermal hyperplasia with thick suprapapillary plates and hypergranulosis (Figure 2A) along with alternating orthokeratosis and parakeratosis in vertical and horizontal directions (checkerboard parakeratosis)(Figure 2B). Follicular plugging with shoulder parakeratosis also was seen. The dermis showed a mild, superficial, perivascular lymphohistiocytic infiltrate. These features were diagnostic of pityriasis rubra pilaris (PRP). The patient received acitretin 25 mg/d and methotrexate 17.5 mg/wk (0.4 mg/kg/wk) and showed marked improvement after 2 months of therapy.

Pityriasis rubra pilaris is a rare papulosquamous skin disease of unknown etiology with several theories including genetic factors, aberrant metabolism of vitamin A, infection, drug reaction, autoimmune disease, and malignancy.¹ Clinically, there are 6 types of PRP: type I (classical adult), type II (atypical adult), type III (classical juvenile), type IV (circumscribed juvenile), type V (atypical juvenile), and type VI (HIV associated). Classic features include orange-red keratotic follicular papules that coalesce into plaques with characteristic islands of sparing.¹

Pityriasis rubra pilaris is a rare sequela following administration of certain vaccines, including diphtheria, pertussis, and tetanus; measles-mumps-rubella; and polio vaccines.^2,3 Among the various skin reactions that have been reported following COVID-19 vaccination, PRP has been reported in 19 patients: 7 (36.8%) after AstraZeneca vaccination, 3 (15.8%) after CoronaVac, 3 (15.8%) after Moderna, 5 (26.3%) after Pfizer-BioNTech,⁴ and 1 (5.3%) after Sinopharm.⁵ Our patient represents an additional case of a reaction after the Sinopharm vaccine. The condition developed after the first dose of vaccine in 11 patients, after the second dose in 6 patients, and after the third dose in 2 patients.

Other papulosquamous skin reactions have been reported after the Sinopharm BBIBP-CorV vaccine including psoriasis, lichen planus, and pityriasis rosea. Skin manifestations occurred sporadically, as some happened after the first or second dose or even after booster doses. The exact pathogenic mechanism(s) underlying the development of these conditions following vaccination still are not understood, though they may be attributed to COVID-19 vaccine–induced immune dysregulation.⁶

Pityriasis rubra pilaris can be self-limited in some cases and may not require treatment. Topical therapies such as keratolytics, emollients, and vitamin D may be utilized, especially for localized disease. Systemic therapy may be needed for refractory cases, including retinoids or immunosuppressive medications such as methotrexate, which is considered a second-line treatment for refractory PRP (after retinoids) and was used in our case. Azathioprine and cyclosporine also may be used. Phototherapy may play a role in PRP treatment, but the response is variable.⁷

Pityriasis rubra pilaris should be added to the list of cutaneous adverse reactions that can occur following vaccination with the Sinopharm BBIBP-CorV vaccine. Dermatologists must be aware of the possibility of vaccine-induced PRP, especially in de novo cases.

To the Editor:

A 32-year-old man presented to our clinic with acute-onset erythroderma associated with severe itching of 1 month’s duration. The patient developed the eruption after receiving the second dose of the Sinopharm BBIBP COVID-19 vaccine (BBIBP-CorV) 2 weeks prior to presentation. His medical history was unremarkable. There was no personal or family history of skin disease and no history of drug intake. Physical examination revealed orange-red erythroderma (Figure 1A) with islands of sparing,keratotic follicular orange-red papules on both legs and feet (Figure 1B), well-defined waxy palmoplantar keratoderma (Figures 1C and 1D), and fine scales on the face and scalp. The clinical and laboratory workup were normal, including a negative test for HIV infection.

Histopathology of two 4-mm punch biopsies of the skin on the trunk and lower limb showed irregular epidermal hyperplasia with thick suprapapillary plates and hypergranulosis (Figure 2A) along with alternating orthokeratosis and parakeratosis in vertical and horizontal directions (checkerboard parakeratosis)(Figure 2B). Follicular plugging with shoulder parakeratosis also was seen. The dermis showed a mild, superficial, perivascular lymphohistiocytic infiltrate. These features were diagnostic of pityriasis rubra pilaris (PRP). The patient received acitretin 25 mg/d and methotrexate 17.5 mg/wk (0.4 mg/kg/wk) and showed marked improvement after 2 months of therapy.

Pityriasis rubra pilaris is a rare papulosquamous skin disease of unknown etiology with several theories including genetic factors, aberrant metabolism of vitamin A, infection, drug reaction, autoimmune disease, and malignancy.¹ Clinically, there are 6 types of PRP: type I (classical adult), type II (atypical adult), type III (classical juvenile), type IV (circumscribed juvenile), type V (atypical juvenile), and type VI (HIV associated). Classic features include orange-red keratotic follicular papules that coalesce into plaques with characteristic islands of sparing.¹

Pityriasis rubra pilaris is a rare sequela following administration of certain vaccines, including diphtheria, pertussis, and tetanus; measles-mumps-rubella; and polio vaccines.^2,3 Among the various skin reactions that have been reported following COVID-19 vaccination, PRP has been reported in 19 patients: 7 (36.8%) after AstraZeneca vaccination, 3 (15.8%) after CoronaVac, 3 (15.8%) after Moderna, 5 (26.3%) after Pfizer-BioNTech,⁴ and 1 (5.3%) after Sinopharm.⁵ Our patient represents an additional case of a reaction after the Sinopharm vaccine. The condition developed after the first dose of vaccine in 11 patients, after the second dose in 6 patients, and after the third dose in 2 patients.

Other papulosquamous skin reactions have been reported after the Sinopharm BBIBP-CorV vaccine including psoriasis, lichen planus, and pityriasis rosea. Skin manifestations occurred sporadically, as some happened after the first or second dose or even after booster doses. The exact pathogenic mechanism(s) underlying the development of these conditions following vaccination still are not understood, though they may be attributed to COVID-19 vaccine–induced immune dysregulation.⁶

Pityriasis rubra pilaris can be self-limited in some cases and may not require treatment. Topical therapies such as keratolytics, emollients, and vitamin D may be utilized, especially for localized disease. Systemic therapy may be needed for refractory cases, including retinoids or immunosuppressive medications such as methotrexate, which is considered a second-line treatment for refractory PRP (after retinoids) and was used in our case. Azathioprine and cyclosporine also may be used. Phototherapy may play a role in PRP treatment, but the response is variable.⁷

Pityriasis rubra pilaris should be added to the list of cutaneous adverse reactions that can occur following vaccination with the Sinopharm BBIBP-CorV vaccine. Dermatologists must be aware of the possibility of vaccine-induced PRP, especially in de novo cases.

To the Editor:

A 32-year-old man presented to our clinic with acute-onset erythroderma associated with severe itching of 1 month’s duration. The patient developed the eruption after receiving the second dose of the Sinopharm BBIBP COVID-19 vaccine (BBIBP-CorV) 2 weeks prior to presentation. His medical history was unremarkable. There was no personal or family history of skin disease and no history of drug intake. Physical examination revealed orange-red erythroderma (Figure 1A) with islands of sparing,keratotic follicular orange-red papules on both legs and feet (Figure 1B), well-defined waxy palmoplantar keratoderma (Figures 1C and 1D), and fine scales on the face and scalp. The clinical and laboratory workup were normal, including a negative test for HIV infection.

Histopathology of two 4-mm punch biopsies of the skin on the trunk and lower limb showed irregular epidermal hyperplasia with thick suprapapillary plates and hypergranulosis (Figure 2A) along with alternating orthokeratosis and parakeratosis in vertical and horizontal directions (checkerboard parakeratosis)(Figure 2B). Follicular plugging with shoulder parakeratosis also was seen. The dermis showed a mild, superficial, perivascular lymphohistiocytic infiltrate. These features were diagnostic of pityriasis rubra pilaris (PRP). The patient received acitretin 25 mg/d and methotrexate 17.5 mg/wk (0.4 mg/kg/wk) and showed marked improvement after 2 months of therapy.

Pityriasis rubra pilaris is a rare papulosquamous skin disease of unknown etiology with several theories including genetic factors, aberrant metabolism of vitamin A, infection, drug reaction, autoimmune disease, and malignancy.¹ Clinically, there are 6 types of PRP: type I (classical adult), type II (atypical adult), type III (classical juvenile), type IV (circumscribed juvenile), type V (atypical juvenile), and type VI (HIV associated). Classic features include orange-red keratotic follicular papules that coalesce into plaques with characteristic islands of sparing.¹

Pityriasis rubra pilaris is a rare sequela following administration of certain vaccines, including diphtheria, pertussis, and tetanus; measles-mumps-rubella; and polio vaccines.^2,3 Among the various skin reactions that have been reported following COVID-19 vaccination, PRP has been reported in 19 patients: 7 (36.8%) after AstraZeneca vaccination, 3 (15.8%) after CoronaVac, 3 (15.8%) after Moderna, 5 (26.3%) after Pfizer-BioNTech,⁴ and 1 (5.3%) after Sinopharm.⁵ Our patient represents an additional case of a reaction after the Sinopharm vaccine. The condition developed after the first dose of vaccine in 11 patients, after the second dose in 6 patients, and after the third dose in 2 patients.

Other papulosquamous skin reactions have been reported after the Sinopharm BBIBP-CorV vaccine including psoriasis, lichen planus, and pityriasis rosea. Skin manifestations occurred sporadically, as some happened after the first or second dose or even after booster doses. The exact pathogenic mechanism(s) underlying the development of these conditions following vaccination still are not understood, though they may be attributed to COVID-19 vaccine–induced immune dysregulation.⁶

Pityriasis rubra pilaris can be self-limited in some cases and may not require treatment. Topical therapies such as keratolytics, emollients, and vitamin D may be utilized, especially for localized disease. Systemic therapy may be needed for refractory cases, including retinoids or immunosuppressive medications such as methotrexate, which is considered a second-line treatment for refractory PRP (after retinoids) and was used in our case. Azathioprine and cyclosporine also may be used. Phototherapy may play a role in PRP treatment, but the response is variable.⁷

Pityriasis rubra pilaris should be added to the list of cutaneous adverse reactions that can occur following vaccination with the Sinopharm BBIBP-CorV vaccine. Dermatologists must be aware of the possibility of vaccine-induced PRP, especially in de novo cases.

The Diagnosis: Erythrodermic Allergic Contact Dermatitis

The worsening symptoms in our patient prompted intervention rather than observation and reassurance. Contact allergy to lanolin was suspected given the worsening presentation after the addition of Minerin, which was immediately discontinued. The patient’s family applied betamethasone cream 0.1% twice daily to severe plaques, pimecrolimus cream 1% to the face, and triamcinolone cream 0.1% to the rest of the body. At follow-up 1 week later, he experienced complete resolution of symptoms, which supported the diagnosis of erythrodermic allergic contact dermatitis (ACD).

The prevalence of ACD caused by lanolin varies among the general population from 1.2% to 6.9%.¹ Lanolin recently was named Allergen of the Year in 2023 by the American Contact Dermatitis Society.² It can be found in various commercial products, including creams, soaps, and ointments. Atopic dermatitis (AD) is a common pediatric inflammatory skin disorder that typically is treated with these products.³ In a study analyzing 533 products, up to 6% of skin care products for babies and children contained lanolin.⁴ Therefore, exposure to lanolin-containing products may be fairly common in the pediatric population.

Lanolin is a fatlike substance derived from sheep sebaceous gland secretions and extracted from sheep’s wool. Its composition varies by sheep breed, location, and extraction and purification methods. The most common allergens involve the alcoholic fraction produced by hydrolysis of lanolin.⁴ In 1996, Wolf⁵ described the “lanolin paradox,” which argued the difficulty with identifying lanolin as an allergen (similar to Fisher’s “paraben paradox”) based on 4 principles: (1) lanolin-containing topical medicaments tend to be more sensitizing than lanolin-containing cosmetics; (2) patients with ACD after applying lanolin-containing topical medicaments to damaged or ulcerated skin often can apply lanolin-containing cosmetics to normal or unaffected skin without a reaction; (3) false-negative patch test results often occur in lanolin-sensitive patients; and (4) patch testing with a single lanolin-containing agent (lanolin alcohol [30% in petrolatum]) is an unreliable and inadequate method of detecting lanolin allergy.^6,7 This theory elucidates the challenge of diagnosing contact allergies, particularly lanolin contact allergies.

Clinical features of acute ACD vary by skin type. Lighter skin types may have well-demarcated, pruritic, eczematous patches and plaques affecting the flexor surfaces. Asian patients may present with psoriasiform plaques with more well-demarcated borders and increased scaling and lichenification. In patients with darker skin types, dermatitis may manifest as papulation, lichenification, and color changes (violet, gray, or darker brown) along extensor surfaces.8 Chronic dermatitis manifests as lichenified scaly plaques. Given the diversity in dermatitis manifestation and the challenges of identifying erythema, especially in skin of color, clinicians may misidentify disease severity. These features aid in diagnosing and treating patients presenting with diffuse erythroderma and worsening eczematous patches and plaques despite use of typical topical treatments.

The differential diagnosis includes irritant contact dermatitis, AD, seborrheic dermatitis, and chronic plaque psoriasis. Negative patch testing suggests contact dermatitis based on exposure to a product. A thorough medication and personal history helps distinguish ACD from AD. Atopic dermatitis classically appears on the flexural areas, face, eyelids, and hands of patients with a personal or family history of atopy. Greasy scaly plaques on the central part of the face, eyelids, and scalp commonly are found in seborrheic dermatitis. In chronic plaque psoriasis, lesions typically are described as welldemarcated, inflamed plaques with notable scale located primarily in the scalp and diaper area in newborns and children until the age of 2 years. Our patient presented with scaly plaques throughout most of the body. The history of Minerin use over the course of 3 to 5 months and worsening skin eruptions involving a majority of the skin surface suggested continued exposure.

Patch testing assists in the diagnosis of ACD, with varying results due to manufacturing and processing inconsistencies in the composition of various substances used in the standard test sets, often making it difficult to diagnose lanolin as an allergen. According to Lee and Warshaw,6 the lack of uniformity within testing of lanolin-containing products may cause false-positive results, poor patch-test reproducibility, and loss of allergic contact response. A 2019 study utilized a combination of Amerchol L101 and lanolin alcohol to improve the diagnosis of lanolin allergy, as standard testing may not identify patients with lanolin sensitivities.1 A study with the North American Contact Dermatitis Group from 2005 to 2012 demonstrated that positive patch testing among children was the most consistent method for diagnosing ACD, and results were clinically relevant.⁹ However, the different lanolin-containing products are not standardized in patch testing, which often causes mixed reactions and does not definitely demonstrate classic positive results, even with the use of repeated open application tests.² Although there has been an emphasis on refining the standardization of the lanolin used for patch testing, lanolin contact allergy remains a predominantly clinical diagnosis.

Both AD and ACD are common pediatric skin findings, and mixed positive and neutral associations between AD and allergy to lanolin have been described in a few studies.^1,3,9,10 A history of atopy is more notable in a pediatric patient vs an adult, as sensitivities tend to subside into adulthood.⁹ Further studies and more precise testing are needed to investigate the relationship between AD and ACD.

The Diagnosis: Erythrodermic Allergic Contact Dermatitis

The worsening symptoms in our patient prompted intervention rather than observation and reassurance. Contact allergy to lanolin was suspected given the worsening presentation after the addition of Minerin, which was immediately discontinued. The patient’s family applied betamethasone cream 0.1% twice daily to severe plaques, pimecrolimus cream 1% to the face, and triamcinolone cream 0.1% to the rest of the body. At follow-up 1 week later, he experienced complete resolution of symptoms, which supported the diagnosis of erythrodermic allergic contact dermatitis (ACD).

The prevalence of ACD caused by lanolin varies among the general population from 1.2% to 6.9%.¹ Lanolin recently was named Allergen of the Year in 2023 by the American Contact Dermatitis Society.² It can be found in various commercial products, including creams, soaps, and ointments. Atopic dermatitis (AD) is a common pediatric inflammatory skin disorder that typically is treated with these products.³ In a study analyzing 533 products, up to 6% of skin care products for babies and children contained lanolin.⁴ Therefore, exposure to lanolin-containing products may be fairly common in the pediatric population.

Lanolin is a fatlike substance derived from sheep sebaceous gland secretions and extracted from sheep’s wool. Its composition varies by sheep breed, location, and extraction and purification methods. The most common allergens involve the alcoholic fraction produced by hydrolysis of lanolin.⁴ In 1996, Wolf⁵ described the “lanolin paradox,” which argued the difficulty with identifying lanolin as an allergen (similar to Fisher’s “paraben paradox”) based on 4 principles: (1) lanolin-containing topical medicaments tend to be more sensitizing than lanolin-containing cosmetics; (2) patients with ACD after applying lanolin-containing topical medicaments to damaged or ulcerated skin often can apply lanolin-containing cosmetics to normal or unaffected skin without a reaction; (3) false-negative patch test results often occur in lanolin-sensitive patients; and (4) patch testing with a single lanolin-containing agent (lanolin alcohol [30% in petrolatum]) is an unreliable and inadequate method of detecting lanolin allergy.^6,7 This theory elucidates the challenge of diagnosing contact allergies, particularly lanolin contact allergies.

Clinical features of acute ACD vary by skin type. Lighter skin types may have well-demarcated, pruritic, eczematous patches and plaques affecting the flexor surfaces. Asian patients may present with psoriasiform plaques with more well-demarcated borders and increased scaling and lichenification. In patients with darker skin types, dermatitis may manifest as papulation, lichenification, and color changes (violet, gray, or darker brown) along extensor surfaces.8 Chronic dermatitis manifests as lichenified scaly plaques. Given the diversity in dermatitis manifestation and the challenges of identifying erythema, especially in skin of color, clinicians may misidentify disease severity. These features aid in diagnosing and treating patients presenting with diffuse erythroderma and worsening eczematous patches and plaques despite use of typical topical treatments.

The differential diagnosis includes irritant contact dermatitis, AD, seborrheic dermatitis, and chronic plaque psoriasis. Negative patch testing suggests contact dermatitis based on exposure to a product. A thorough medication and personal history helps distinguish ACD from AD. Atopic dermatitis classically appears on the flexural areas, face, eyelids, and hands of patients with a personal or family history of atopy. Greasy scaly plaques on the central part of the face, eyelids, and scalp commonly are found in seborrheic dermatitis. In chronic plaque psoriasis, lesions typically are described as welldemarcated, inflamed plaques with notable scale located primarily in the scalp and diaper area in newborns and children until the age of 2 years. Our patient presented with scaly plaques throughout most of the body. The history of Minerin use over the course of 3 to 5 months and worsening skin eruptions involving a majority of the skin surface suggested continued exposure.

Patch testing assists in the diagnosis of ACD, with varying results due to manufacturing and processing inconsistencies in the composition of various substances used in the standard test sets, often making it difficult to diagnose lanolin as an allergen. According to Lee and Warshaw,6 the lack of uniformity within testing of lanolin-containing products may cause false-positive results, poor patch-test reproducibility, and loss of allergic contact response. A 2019 study utilized a combination of Amerchol L101 and lanolin alcohol to improve the diagnosis of lanolin allergy, as standard testing may not identify patients with lanolin sensitivities.1 A study with the North American Contact Dermatitis Group from 2005 to 2012 demonstrated that positive patch testing among children was the most consistent method for diagnosing ACD, and results were clinically relevant.⁹ However, the different lanolin-containing products are not standardized in patch testing, which often causes mixed reactions and does not definitely demonstrate classic positive results, even with the use of repeated open application tests.² Although there has been an emphasis on refining the standardization of the lanolin used for patch testing, lanolin contact allergy remains a predominantly clinical diagnosis.

Both AD and ACD are common pediatric skin findings, and mixed positive and neutral associations between AD and allergy to lanolin have been described in a few studies.^1,3,9,10 A history of atopy is more notable in a pediatric patient vs an adult, as sensitivities tend to subside into adulthood.⁹ Further studies and more precise testing are needed to investigate the relationship between AD and ACD.

The Diagnosis: Erythrodermic Allergic Contact Dermatitis

The worsening symptoms in our patient prompted intervention rather than observation and reassurance. Contact allergy to lanolin was suspected given the worsening presentation after the addition of Minerin, which was immediately discontinued. The patient’s family applied betamethasone cream 0.1% twice daily to severe plaques, pimecrolimus cream 1% to the face, and triamcinolone cream 0.1% to the rest of the body. At follow-up 1 week later, he experienced complete resolution of symptoms, which supported the diagnosis of erythrodermic allergic contact dermatitis (ACD).

The prevalence of ACD caused by lanolin varies among the general population from 1.2% to 6.9%.¹ Lanolin recently was named Allergen of the Year in 2023 by the American Contact Dermatitis Society.² It can be found in various commercial products, including creams, soaps, and ointments. Atopic dermatitis (AD) is a common pediatric inflammatory skin disorder that typically is treated with these products.³ In a study analyzing 533 products, up to 6% of skin care products for babies and children contained lanolin.⁴ Therefore, exposure to lanolin-containing products may be fairly common in the pediatric population.

Lanolin is a fatlike substance derived from sheep sebaceous gland secretions and extracted from sheep’s wool. Its composition varies by sheep breed, location, and extraction and purification methods. The most common allergens involve the alcoholic fraction produced by hydrolysis of lanolin.⁴ In 1996, Wolf⁵ described the “lanolin paradox,” which argued the difficulty with identifying lanolin as an allergen (similar to Fisher’s “paraben paradox”) based on 4 principles: (1) lanolin-containing topical medicaments tend to be more sensitizing than lanolin-containing cosmetics; (2) patients with ACD after applying lanolin-containing topical medicaments to damaged or ulcerated skin often can apply lanolin-containing cosmetics to normal or unaffected skin without a reaction; (3) false-negative patch test results often occur in lanolin-sensitive patients; and (4) patch testing with a single lanolin-containing agent (lanolin alcohol [30% in petrolatum]) is an unreliable and inadequate method of detecting lanolin allergy.^6,7 This theory elucidates the challenge of diagnosing contact allergies, particularly lanolin contact allergies.

Clinical features of acute ACD vary by skin type. Lighter skin types may have well-demarcated, pruritic, eczematous patches and plaques affecting the flexor surfaces. Asian patients may present with psoriasiform plaques with more well-demarcated borders and increased scaling and lichenification. In patients with darker skin types, dermatitis may manifest as papulation, lichenification, and color changes (violet, gray, or darker brown) along extensor surfaces.8 Chronic dermatitis manifests as lichenified scaly plaques. Given the diversity in dermatitis manifestation and the challenges of identifying erythema, especially in skin of color, clinicians may misidentify disease severity. These features aid in diagnosing and treating patients presenting with diffuse erythroderma and worsening eczematous patches and plaques despite use of typical topical treatments.

The differential diagnosis includes irritant contact dermatitis, AD, seborrheic dermatitis, and chronic plaque psoriasis. Negative patch testing suggests contact dermatitis based on exposure to a product. A thorough medication and personal history helps distinguish ACD from AD. Atopic dermatitis classically appears on the flexural areas, face, eyelids, and hands of patients with a personal or family history of atopy. Greasy scaly plaques on the central part of the face, eyelids, and scalp commonly are found in seborrheic dermatitis. In chronic plaque psoriasis, lesions typically are described as welldemarcated, inflamed plaques with notable scale located primarily in the scalp and diaper area in newborns and children until the age of 2 years. Our patient presented with scaly plaques throughout most of the body. The history of Minerin use over the course of 3 to 5 months and worsening skin eruptions involving a majority of the skin surface suggested continued exposure.

Patch testing assists in the diagnosis of ACD, with varying results due to manufacturing and processing inconsistencies in the composition of various substances used in the standard test sets, often making it difficult to diagnose lanolin as an allergen. According to Lee and Warshaw,6 the lack of uniformity within testing of lanolin-containing products may cause false-positive results, poor patch-test reproducibility, and loss of allergic contact response. A 2019 study utilized a combination of Amerchol L101 and lanolin alcohol to improve the diagnosis of lanolin allergy, as standard testing may not identify patients with lanolin sensitivities.1 A study with the North American Contact Dermatitis Group from 2005 to 2012 demonstrated that positive patch testing among children was the most consistent method for diagnosing ACD, and results were clinically relevant.⁹ However, the different lanolin-containing products are not standardized in patch testing, which often causes mixed reactions and does not definitely demonstrate classic positive results, even with the use of repeated open application tests.² Although there has been an emphasis on refining the standardization of the lanolin used for patch testing, lanolin contact allergy remains a predominantly clinical diagnosis.

Both AD and ACD are common pediatric skin findings, and mixed positive and neutral associations between AD and allergy to lanolin have been described in a few studies.^1,3,9,10 A history of atopy is more notable in a pediatric patient vs an adult, as sensitivities tend to subside into adulthood.⁹ Further studies and more precise testing are needed to investigate the relationship between AD and ACD.

Plant Parts and Nomenclature

Ficus carica (common fig) is a deciduous shrub or small tree with smooth gray bark that can grow up to 10 m in height (Figure 1). It is characterized by many spreading branches, but the trunk rarely grows beyond a diameter of 7 in. Its hairy leaves are coarse on the upper side and soft underneath with 3 to 7 deep lobes that can extend up to 25 cm in length or width; the leaves grow individually, alternating along the sides of the branches. Fig trees often can be seen adorning yards, gardens, and parks, especially in tropical and subtropical climates. Ficus carica should not be confused with Ficus benjamina (weeping fig), a common ornamental tree that also is used to provide shade in hot climates, though both can cause phototoxic skin eruptions.

The common fig tree originated in the Mediterranean and western Asia¹ and has been cultivated by humans since the second and third millennia bc for its fruit, which commonly is used to sweeten cookies, cakes, and jams.² Figs are the most commonly mentioned food plant in the Bible, with at least 56 references in the Old and New Testaments.³ The “fruit” technically is a syconium—a hollow fleshy receptacle with a small opening at the apex partly closed by small scales. It can be obovoid, turbinate, or pear shaped; can be 1 to 4 inches long; and can vary in color from yellowish green to coppery, bronze, or dark purple (Figure 2).

Ficus carica is a member of the Moraceae family (derived from the Latin name for the mulberry tree), which includes 53 genera and approximately 1400 species, of which about 850 belong to the genus Ficus (the Latin name for a fig tree). The term carica likely comes from the Latin word carricare (to load) to describe a tree loaded with figs. Family members include trees, shrubs, lianas, and herbs that usually contain laticifers with a milky latex.

Traditional Uses

For centuries, components of the fig tree have been used in herbal teas and pastes to treat ailments ranging from sore throats to diarrhea, though there is no evidence to support their efficacy.⁴ Ancient Indians and Egyptians used plants such as the common fig tree containing furocoumarins to induce hyperpigmentation in vitiligo.⁵

Phototoxic Components

The leaves and sap of the common fig tree contain psoralens, which are members of the furocoumarin group of chemical compounds and are the source of its phototoxicity. The fruit does not contain psoralens.^6-9 The tree also produces proteolytic enzymes such as protease, amylase, ficin, triterpenoids, and lipodiastase that enhance its phototoxic effects.⁸ Exposure to UV light between 320 and 400 nm following contact with these phototoxic components triggers a reaction in the skin over the course of 1 to 3 days.⁵ The psoralens bind in epidermal cells, cross-link the DNA, and cause cell-membrane destruction, leading to edema and necrosis.¹⁰ The delay in symptoms may be attributed to the time needed to synthesize acute-phase reaction proteins such as tumor necrosis factor α and IL-1.¹¹ In spring and summer months, an increased concentration of psoralens in the leaves and sap contribute to an increased incidence of phytophotodermatitis.⁹ Humidity and sweat also increase the percutaneous absorption of psoralens.^12,13

Allergens

Fig trees produce a latex protein that can cause cross-reactive hypersensitivity reactions in those allergic to F benjamina latex and rubber latex.⁶ The latex proteins in fig trees can act as airborne respiratory allergens. Ingestion of figs can produce anaphylactic reactions in those sensitized to rubber latex and F benjamina latex.⁷ Other plant families associated with phototoxic reactions include Rutaceae (lemon, lime, bitter orange), Apiaceae (formerly Umbelliferae)(carrot, parsnip, parsley, dill, celery, hogweed), and Fabaceae (prairie turnip).

Most cases of fig phytophotodermatitis begin with burning, pain, and/or itching within hours of sunlight exposure in areas of the skin that encountered components of the fig tree, often in a linear pattern. The affected areas become erythematous and edematous with formation of bullae and unilocular vesicles over the course of 1 to 3 days.^12,14,15 Lesions may extend beyond the region of contact with the fig tree as they spread across the skin due to sweat or friction, and pain may linger even after the lesions resolve.^12,13,16 Adults who handle fig trees (eg, pruning) are susceptible to phototoxic reactions, especially those using chain saws or other mechanisms that result in spray exposure, as the photosensitizing sap permeates the wood and bark of the entire tree.¹⁷ Similarly, children who handle fig leaves or sap during outdoor play can develop bullous eruptions. Severe cases have resulted in hospital admission after prolonged exposure.¹⁶ Additionally, irritant dermatitis may arise from contact with the trichomes or “hairs” on various parts of the plant.

Image provided with permission by Scott Norton, MD, MPH, MSc (Washington, DC).

Patients who use natural remedies containing components of the fig tree without the supervision of a medical provider put themselves at risk for unsafe or unwanted adverse effects, such as phytophotodermatitis.^12,15,16,18 An entire family presented with burns after they applied fig leaf extract to the skin prior to tanning outside in the sun.¹⁹ A 42-year-old woman acquired a severe burn covering 81% of the body surface after topically applying fig leaf tea to the skin as a tanning agent.²⁰ A subset of patients ingesting or applying fig tree components for conditions such as vitiligo, dermatitis, onychomycosis, and motor retardation developed similar cutaneous reactions.^13,14,21,22 Lesions resembling finger marks can raise concerns for potential abuse or neglect in children.²²

The differential diagnosis for fig phytophotodermatitis includes sunburn, chemical burns, drug-related photosensitivity, infectious lesions (eg, herpes simplex, bullous impetigo, Lyme disease, superficial lymphangitis), connective tissue disease (eg, systemic lupus erythematosus), contact dermatitis, and nonaccidental trauma.^12,15,18 Compared to sunburn, phytophotodermatitis tends to increase in severity over days following exposure and heals with dramatic hyperpigmentation, which also prompts visits to dermatology.¹²

Treatment

Treatment of fig phytophotodermatitis chiefly is symptomatic, including analgesia, appropriate wound care, and infection prophylaxis. Topical and systemic corticosteroids may aid in the resolution of moderate to severe reactions.^15,23,24 Even severe injuries over small areas or mild injuries to a high percentage of the total body surface area may require treatment in a burn unit. Patients should be encouraged to use mineral-based sunscreens on the affected areas to reduce the risk for hyperpigmentation. Individuals who regularly handle fig trees should use contact barriers including gloves and protective clothing (eg, long-sleeved shirts, long pants).

Plant Parts and Nomenclature

Ficus carica (common fig) is a deciduous shrub or small tree with smooth gray bark that can grow up to 10 m in height (Figure 1). It is characterized by many spreading branches, but the trunk rarely grows beyond a diameter of 7 in. Its hairy leaves are coarse on the upper side and soft underneath with 3 to 7 deep lobes that can extend up to 25 cm in length or width; the leaves grow individually, alternating along the sides of the branches. Fig trees often can be seen adorning yards, gardens, and parks, especially in tropical and subtropical climates. Ficus carica should not be confused with Ficus benjamina (weeping fig), a common ornamental tree that also is used to provide shade in hot climates, though both can cause phototoxic skin eruptions.

The common fig tree originated in the Mediterranean and western Asia¹ and has been cultivated by humans since the second and third millennia bc for its fruit, which commonly is used to sweeten cookies, cakes, and jams.² Figs are the most commonly mentioned food plant in the Bible, with at least 56 references in the Old and New Testaments.³ The “fruit” technically is a syconium—a hollow fleshy receptacle with a small opening at the apex partly closed by small scales. It can be obovoid, turbinate, or pear shaped; can be 1 to 4 inches long; and can vary in color from yellowish green to coppery, bronze, or dark purple (Figure 2).

Ficus carica is a member of the Moraceae family (derived from the Latin name for the mulberry tree), which includes 53 genera and approximately 1400 species, of which about 850 belong to the genus Ficus (the Latin name for a fig tree). The term carica likely comes from the Latin word carricare (to load) to describe a tree loaded with figs. Family members include trees, shrubs, lianas, and herbs that usually contain laticifers with a milky latex.

Traditional Uses

For centuries, components of the fig tree have been used in herbal teas and pastes to treat ailments ranging from sore throats to diarrhea, though there is no evidence to support their efficacy.⁴ Ancient Indians and Egyptians used plants such as the common fig tree containing furocoumarins to induce hyperpigmentation in vitiligo.⁵

Phototoxic Components

The leaves and sap of the common fig tree contain psoralens, which are members of the furocoumarin group of chemical compounds and are the source of its phototoxicity. The fruit does not contain psoralens.^6-9 The tree also produces proteolytic enzymes such as protease, amylase, ficin, triterpenoids, and lipodiastase that enhance its phototoxic effects.⁸ Exposure to UV light between 320 and 400 nm following contact with these phototoxic components triggers a reaction in the skin over the course of 1 to 3 days.⁵ The psoralens bind in epidermal cells, cross-link the DNA, and cause cell-membrane destruction, leading to edema and necrosis.¹⁰ The delay in symptoms may be attributed to the time needed to synthesize acute-phase reaction proteins such as tumor necrosis factor α and IL-1.¹¹ In spring and summer months, an increased concentration of psoralens in the leaves and sap contribute to an increased incidence of phytophotodermatitis.⁹ Humidity and sweat also increase the percutaneous absorption of psoralens.^12,13

Allergens

Fig trees produce a latex protein that can cause cross-reactive hypersensitivity reactions in those allergic to F benjamina latex and rubber latex.⁶ The latex proteins in fig trees can act as airborne respiratory allergens. Ingestion of figs can produce anaphylactic reactions in those sensitized to rubber latex and F benjamina latex.⁷ Other plant families associated with phototoxic reactions include Rutaceae (lemon, lime, bitter orange), Apiaceae (formerly Umbelliferae)(carrot, parsnip, parsley, dill, celery, hogweed), and Fabaceae (prairie turnip).

Most cases of fig phytophotodermatitis begin with burning, pain, and/or itching within hours of sunlight exposure in areas of the skin that encountered components of the fig tree, often in a linear pattern. The affected areas become erythematous and edematous with formation of bullae and unilocular vesicles over the course of 1 to 3 days.^12,14,15 Lesions may extend beyond the region of contact with the fig tree as they spread across the skin due to sweat or friction, and pain may linger even after the lesions resolve.^12,13,16 Adults who handle fig trees (eg, pruning) are susceptible to phototoxic reactions, especially those using chain saws or other mechanisms that result in spray exposure, as the photosensitizing sap permeates the wood and bark of the entire tree.¹⁷ Similarly, children who handle fig leaves or sap during outdoor play can develop bullous eruptions. Severe cases have resulted in hospital admission after prolonged exposure.¹⁶ Additionally, irritant dermatitis may arise from contact with the trichomes or “hairs” on various parts of the plant.

Image provided with permission by Scott Norton, MD, MPH, MSc (Washington, DC).

Patients who use natural remedies containing components of the fig tree without the supervision of a medical provider put themselves at risk for unsafe or unwanted adverse effects, such as phytophotodermatitis.^12,15,16,18 An entire family presented with burns after they applied fig leaf extract to the skin prior to tanning outside in the sun.¹⁹ A 42-year-old woman acquired a severe burn covering 81% of the body surface after topically applying fig leaf tea to the skin as a tanning agent.²⁰ A subset of patients ingesting or applying fig tree components for conditions such as vitiligo, dermatitis, onychomycosis, and motor retardation developed similar cutaneous reactions.^13,14,21,22 Lesions resembling finger marks can raise concerns for potential abuse or neglect in children.²²

The differential diagnosis for fig phytophotodermatitis includes sunburn, chemical burns, drug-related photosensitivity, infectious lesions (eg, herpes simplex, bullous impetigo, Lyme disease, superficial lymphangitis), connective tissue disease (eg, systemic lupus erythematosus), contact dermatitis, and nonaccidental trauma.^12,15,18 Compared to sunburn, phytophotodermatitis tends to increase in severity over days following exposure and heals with dramatic hyperpigmentation, which also prompts visits to dermatology.¹²

Treatment

Treatment of fig phytophotodermatitis chiefly is symptomatic, including analgesia, appropriate wound care, and infection prophylaxis. Topical and systemic corticosteroids may aid in the resolution of moderate to severe reactions.^15,23,24 Even severe injuries over small areas or mild injuries to a high percentage of the total body surface area may require treatment in a burn unit. Patients should be encouraged to use mineral-based sunscreens on the affected areas to reduce the risk for hyperpigmentation. Individuals who regularly handle fig trees should use contact barriers including gloves and protective clothing (eg, long-sleeved shirts, long pants).

Plant Parts and Nomenclature

Ficus carica (common fig) is a deciduous shrub or small tree with smooth gray bark that can grow up to 10 m in height (Figure 1). It is characterized by many spreading branches, but the trunk rarely grows beyond a diameter of 7 in. Its hairy leaves are coarse on the upper side and soft underneath with 3 to 7 deep lobes that can extend up to 25 cm in length or width; the leaves grow individually, alternating along the sides of the branches. Fig trees often can be seen adorning yards, gardens, and parks, especially in tropical and subtropical climates. Ficus carica should not be confused with Ficus benjamina (weeping fig), a common ornamental tree that also is used to provide shade in hot climates, though both can cause phototoxic skin eruptions.

The common fig tree originated in the Mediterranean and western Asia¹ and has been cultivated by humans since the second and third millennia bc for its fruit, which commonly is used to sweeten cookies, cakes, and jams.² Figs are the most commonly mentioned food plant in the Bible, with at least 56 references in the Old and New Testaments.³ The “fruit” technically is a syconium—a hollow fleshy receptacle with a small opening at the apex partly closed by small scales. It can be obovoid, turbinate, or pear shaped; can be 1 to 4 inches long; and can vary in color from yellowish green to coppery, bronze, or dark purple (Figure 2).

Ficus carica is a member of the Moraceae family (derived from the Latin name for the mulberry tree), which includes 53 genera and approximately 1400 species, of which about 850 belong to the genus Ficus (the Latin name for a fig tree). The term carica likely comes from the Latin word carricare (to load) to describe a tree loaded with figs. Family members include trees, shrubs, lianas, and herbs that usually contain laticifers with a milky latex.

Traditional Uses

For centuries, components of the fig tree have been used in herbal teas and pastes to treat ailments ranging from sore throats to diarrhea, though there is no evidence to support their efficacy.⁴ Ancient Indians and Egyptians used plants such as the common fig tree containing furocoumarins to induce hyperpigmentation in vitiligo.⁵

Phototoxic Components

The leaves and sap of the common fig tree contain psoralens, which are members of the furocoumarin group of chemical compounds and are the source of its phototoxicity. The fruit does not contain psoralens.^6-9 The tree also produces proteolytic enzymes such as protease, amylase, ficin, triterpenoids, and lipodiastase that enhance its phototoxic effects.⁸ Exposure to UV light between 320 and 400 nm following contact with these phototoxic components triggers a reaction in the skin over the course of 1 to 3 days.⁵ The psoralens bind in epidermal cells, cross-link the DNA, and cause cell-membrane destruction, leading to edema and necrosis.¹⁰ The delay in symptoms may be attributed to the time needed to synthesize acute-phase reaction proteins such as tumor necrosis factor α and IL-1.¹¹ In spring and summer months, an increased concentration of psoralens in the leaves and sap contribute to an increased incidence of phytophotodermatitis.⁹ Humidity and sweat also increase the percutaneous absorption of psoralens.^12,13

Allergens

Fig trees produce a latex protein that can cause cross-reactive hypersensitivity reactions in those allergic to F benjamina latex and rubber latex.⁶ The latex proteins in fig trees can act as airborne respiratory allergens. Ingestion of figs can produce anaphylactic reactions in those sensitized to rubber latex and F benjamina latex.⁷ Other plant families associated with phototoxic reactions include Rutaceae (lemon, lime, bitter orange), Apiaceae (formerly Umbelliferae)(carrot, parsnip, parsley, dill, celery, hogweed), and Fabaceae (prairie turnip).

Most cases of fig phytophotodermatitis begin with burning, pain, and/or itching within hours of sunlight exposure in areas of the skin that encountered components of the fig tree, often in a linear pattern. The affected areas become erythematous and edematous with formation of bullae and unilocular vesicles over the course of 1 to 3 days.^12,14,15 Lesions may extend beyond the region of contact with the fig tree as they spread across the skin due to sweat or friction, and pain may linger even after the lesions resolve.^12,13,16 Adults who handle fig trees (eg, pruning) are susceptible to phototoxic reactions, especially those using chain saws or other mechanisms that result in spray exposure, as the photosensitizing sap permeates the wood and bark of the entire tree.¹⁷ Similarly, children who handle fig leaves or sap during outdoor play can develop bullous eruptions. Severe cases have resulted in hospital admission after prolonged exposure.¹⁶ Additionally, irritant dermatitis may arise from contact with the trichomes or “hairs” on various parts of the plant.

Image provided with permission by Scott Norton, MD, MPH, MSc (Washington, DC).

Patients who use natural remedies containing components of the fig tree without the supervision of a medical provider put themselves at risk for unsafe or unwanted adverse effects, such as phytophotodermatitis.^12,15,16,18 An entire family presented with burns after they applied fig leaf extract to the skin prior to tanning outside in the sun.¹⁹ A 42-year-old woman acquired a severe burn covering 81% of the body surface after topically applying fig leaf tea to the skin as a tanning agent.²⁰ A subset of patients ingesting or applying fig tree components for conditions such as vitiligo, dermatitis, onychomycosis, and motor retardation developed similar cutaneous reactions.^13,14,21,22 Lesions resembling finger marks can raise concerns for potential abuse or neglect in children.²²

The differential diagnosis for fig phytophotodermatitis includes sunburn, chemical burns, drug-related photosensitivity, infectious lesions (eg, herpes simplex, bullous impetigo, Lyme disease, superficial lymphangitis), connective tissue disease (eg, systemic lupus erythematosus), contact dermatitis, and nonaccidental trauma.^12,15,18 Compared to sunburn, phytophotodermatitis tends to increase in severity over days following exposure and heals with dramatic hyperpigmentation, which also prompts visits to dermatology.¹²

Treatment

Treatment of fig phytophotodermatitis chiefly is symptomatic, including analgesia, appropriate wound care, and infection prophylaxis. Topical and systemic corticosteroids may aid in the resolution of moderate to severe reactions.^15,23,24 Even severe injuries over small areas or mild injuries to a high percentage of the total body surface area may require treatment in a burn unit. Patients should be encouraged to use mineral-based sunscreens on the affected areas to reduce the risk for hyperpigmentation. Individuals who regularly handle fig trees should use contact barriers including gloves and protective clothing (eg, long-sleeved shirts, long pants).

In 2023, ESPEN (the European Society for Clinical Nutrition and Metabolism) published consensus recommendations highlighting the importance of regular monitoring and treatment of nutrient deficiencies in patients with inflammatory bowel disease (IBD) for improved prognosis, mortality, and quality of life.¹ Suboptimal nutrition in patients with IBD predominantly results from inflammation of the gastrointestinal (GI) tract leading to malabsorption; however, medications commonly used to manage IBD also can contribute to malnutrition.^2,3 Additionally, patients may develop nausea and food avoidance due to medication or the disease itself, leading to nutritional withdrawal and eventual deficiency.⁴ Even with the development of diets focused on balancing nutritional needs and decreasing inflammation,⁵ offsetting this aversion to food can be difficult to overcome.²

Cutaneous manifestations of IBD are multifaceted and can be secondary to the disease, reactive to or associated with IBD, or effects from nutritional deficiencies. The most common vitamin and nutrient deficiencies in patients with IBD include iron; zinc; calcium; vitamin D; and vitamins B₆ (pyridoxine), B₉ (folic acid), and B₁₂.⁶ Malnutrition may manifest with cutaneous disease, and dermatologists can be the first to identify and assess for nutritional deficiencies. In this article, we review the mechanisms of these micronutrient depletions in the context of IBD, their subsequent dermatologic manifestations (Table), and treatment and monitoring guidelines for each deficiency.

Iron

A systematic review conducted from 2007 to 2012 in European patients with IBD (N=2192) found the overall prevalence of anemia in this population to be 24% (95% CI, 18%-31%), with 57% of patients with anemia experiencing iron deficiency.⁷ Anemia is observed more commonly in patients hospitalized with IBD and is common in patients with both Crohn disease and ulcerative colitis.⁸

Pathophysiology—Iron is critically important in oxygen transportation throughout the body as a major component of hemoglobin. Physiologically, the low pH of the duodenum and proximal jejunum allows divalent metal transporter 1 to transfer dietary Fe³⁺ into enterocytes, where it is reduced to the transportable Fe²⁺.^9,10 Distribution of Fe²⁺ ions from enterocytes relies on ferroportin, an iron-transporting protein, which is heavily regulated by the protein hepcidin.¹¹ Hepcidin, a known acute phase reactant, will increase in the setting of active IBD, causing a depletion of ferroportin and an inability of the body to utilize the stored iron in enterocytes.¹² This poor utilization of iron stores combined with blood loss caused by inflammation in the GI tract is the proposed primary mechanism of iron-deficiency anemia observed in patients with IBD.¹³

Cutaneous Manifestations—From a dermatologic perspective, iron-deficiency anemia can manifest with a wide range of symptoms including glossitis, koilonychia, xerosis and/or pruritus, and brittle hair or hair loss.^14,15 Although the underlying pathophysiology of these cutaneous manifestations is not fully understood, there are several theories assessing the mechanisms behind the skin findings of iron deficiency.

Atrophic glossitis has been observed in many patients with iron deficiency and is thought to manifest due to low iron concentrations in the blood, thereby decreasing oxygen delivery to the papillae of the dorsal tongue with resultant atrophy.^16,17 Similarly, decreased oxygen delivery to the nail bed capillaries may cause deformities in the nail called koilonychia (or “spoon nails”).¹⁸ Iron is a key co-factor in collagen lysyl hydroxylase that promotes collagen binding; iron deficiency may lead to disruptions in the epidermal barrier that can cause pruritus and xerosis.¹⁹ An observational study of 200 healthy patients with a primary concern of pruritus found a correlation between low serum ferritin and a higher degree of pruritus (r=−0.768; P<.00001).²⁰

Evidence for iron’s role in hair growth comes from a mouse model study with a mutation in the serine protease TMPRSS6—a protein that regulates hepcidin and iron absorption—which caused an increase in hepcidin production and subsequent systemic iron deficiency. Mice at 4 weeks of age were devoid of all body hair but had substantial regrowth after initiation of a 2-week iron-rich diet, which suggests a connection between iron repletion and hair growth in mice with iron deficiency.²¹ Additionally, a meta-analysis analyzing the comorbidities of patients with alopecia areata found them to have higher odds (odds ratio [OR]=2.78; 95% CI, 1.23-6.29) of iron-deficiency anemia but no association with IBD (OR=1.48; 95% CI, 0.32-6.82).²²

Diagnosis and Monitoring—The American Gastroenterological Association recommends a complete blood cell count (CBC), serum ferritin, transferrin saturation (TfS), and C-reactive protein (CRP) as standard evaluations for iron deficiency in patients with IBD. Patients with active IBD should be screened every 3 months,and patients with inactive disease should be screened every 6 to 12 months.²³

Although ferritin and TfS often are used as markers for iron status in healthy individuals, they are positive and negative acute phase reactants, respectively. Using them to assess iron status in patients with IBD may inaccurately represent iron status in the setting of inflammation from the disease.²⁴ The European Crohn’s and Colitis Organisation (ECCO) produced guidelines to define iron deficiency as a TfS less than 20% or a ferritin level less than 30 µg/L in patients without evidence of active IBD and a ferritin level less than 100 µg/L for patients with active inflammation.²⁵

A 2020 multicenter observational study of 202 patients with diagnosed IBD found that the ECCO guideline of ferritin less than 30 µg/L had an area under the receiver operating characteristic (AUROC) curve of 0.69, a sensitivity of 0.43, and a specificity of 0.95 in their population.²⁶ In a sensitivity analysis stratifying patients by CRP level (<10 or ≥10 mg/L), the authors found that for patients with ulcerative colitis and a CRP less than 10 mg/L, a cut-off value of ferritin less than 65 µg/L (AUROC=0.78) had a sensitivity of 0.78 and specificity of 0.76, and a TfS value of less than 16% (AUROC=0.88) had a sensitivity of 0.79 and a specificity of 0.9. In patients with a CRP of 10 mg/L or greater, a cut-off value of ferritin 80 µg/L (AUROC=0.76) had a sensitivity of 0.75 and a specificity of 0.82, and a TfS value of less than 11% (AUROC=0.69) had a sensitivity of 0.79 and a specificity of 0.88. There were no ferritin cut-off values associated with good diagnostic performance (defined as both sensitivity and specificity >0.70) for iron deficiency in patients with Crohn disease.²⁶

The authors recommended using an alternative iron measurement such as soluble transferrin receptor (sTfR)/log ferritin ratio (TfR-F) that is not influenced by active inflammation and has a good correlation with ferritin values (TfR-F: r=0.66; P<.001).²⁶ However, both sTfR and TfR-F have high costs and intermethod variability as well as differences in their reference ranges depending on which laboratory performs the analysis, limiting the accessibility and practicality of easily obtaining these tests.²⁷ Although there may be inaccuracies for standard ferritin or TfS under ECCO guidelines, proposed alternatives have their own limitations, which may make ferritin and TfS the most reasonable evaluations of iron status as long as disease activity status at the time of testing is taken into consideration.

Treatment—Treatment of underlying iron deficiency in patients with IBD requires reversing the cause of the deficiency and supplementing iron. In patients with IBD, the options to supplement iron may be limited by active disease, making oral intake less effective. Oral iron supplementation also is associated with notable GI adverse effects that may be exacerbated in patients with IBD. A systematic review of 43 randomized controlled trials (RCTs) evaluating GI adverse effects (eg, nausea, abdominal pain, diarrhea, constipation, and black or tarry stools) of oral ferrous sulfate compared with placebo or intravenous (IV) iron supplementation in healthy nonanemic individuals found a significant increase in GI adverse effects with oral supplementation (placebo: OR=2.32; P<.0001; IV: OR=3.05; P<.0001).²⁸

Therefore, IV iron repletion may be necessary in patients with IBD and may require numerous infusions depending on the formulation of iron. In an RCT conducted in 2011, patients with iron-deficiency anemia with quiescent or mild to moderate IBD were treated with either IV iron sulfate or ferric carboxymaltose.²⁹ With a primary end point of hemoglobin response greater than 2 g/dL, the authors found that 150 of 240 patients responded to ferric carboxymaltose vs 118 of 235 treated with iron sulfate (P=.004). The dosing for ferric carboxymaltose was 1 to 3 infusions of 500 to 1000 mg of iron and for iron sulfate up to 11 infusions of 200 mg of iron.²⁹

Zinc

A systematic review of zinc deficiency in patients with IBD identified 7 studies including 2413 patients and revealed those with Crohn disease had a higher prevalence of zinc deficiency compared with patients with ulcerative colitis (54% vs 41%).³⁰

Pathophysiology—Zinc serves as a catalytic cofactor for enzymatic activity within proteins and immune cells.³¹ The homeostasis of zinc is tightly regulated within the brush border of the small intestine by zinc transporters ZIP4 and ZIP1 from the lumen of enterocytes into the bloodstream.³² Inflammation in the small intestine due to Crohn disease can result in zinc malabsorption.

Ranaldi et al³³ exposed intestinal cells and zinc-depleted intestinal cells to tumor necrosis factor α media to simulate an inflammatory environment. They measured transepithelial electrical resistance as a surrogate for transmembrane permeability and found that zinc-depleted cells had a statistically significantly higher transepithelial electrical resistance percentage (60% reduction after 4 hours; P<1.10^–6) when exposed to tumor necrosis factor α signaling compared with normal intestinal cells. They concluded that zinc deficiency can increase intestinal permeability in the presence of inflammation, creating a cycle of further nutrient malabsorption and inflammation exacerbating IBD symptoms.³³

Cutaneous Manifestations—After absorption in the small intestine, approximately 5% of zinc resides in the skin, with the highest concentration in the stratum spinosum.³⁴ A cell study found that keratinocytes in zinc-deficient environments had higher rates of apoptosis compared with cells in normal media. The authors proposed that this higher rate of apoptosis and the resulting inflammation could be a mechanism for developing the desquamative or eczematous scaly plaques that are common cutaneous manifestations of zinc deficiency.³⁵

Other cutaneous findings may include angular cheilitis, stomatitis, glossitis, paronychia, onychodystrophy, generalized alopecia, and delayed wound healing.³⁶ The histopathology of these skin lesions is characterized by granular layer loss, epidermal pallor, confluent parakeratosis, spongiosis, dyskeratosis, and psoriasiform hyperplasia.³⁷

Diagnosis and Monitoring—Assessing serum zinc levels is challenging, as they may decrease during states of inflammation.³⁸ A mouse model study showed a 3.1-fold increase (P<.001) in ZIP14 expression in wild-type mice compared with an IL-6 -/- knock-down model after IL-6 exposure. The authors concluded that the upregulation of ZIP14 in the liver due to inflammatory cytokine upregulation decreases zinc availability in serum.³⁹ Additionally, serum zinc can overestimate the level of deficiency in IBD because approximately 75% of serum zinc is bound to albumin, which decreases in the setting of inflammation.^40-42

Alternatively, alkaline phosphatase (AP), a zinc-dependent metalloenzyme, may be a better evaluator of zinc status during periods of inflammation. A study in rats evaluated zinc through serum zinc levels and AP levels after a period of induced stress to mimic a short-term inflammatory state.⁴³ The researchers found that total body stores of zinc were unaffected throughout the experiment; only serum zinc declined throughout the experiment duration while AP did not. Because approximately 75% of serum zinc is bound to serum albumin,⁴² the researchers concluded the induced inflammatory state depleted serum albumin and redistributed zinc to the liver, causing the observed serum zinc changes, while total body zinc levels and AP were largely unaffected in comparison.⁴³ Comorbid conditions such as liver or bone disease can increase AP levels, which limits the utility of AP as a surrogate for zinc in patients with comorbidities.⁴⁴ However, even in the context of active IBD, serum zinc still is currently considered the best biomarker to evaluate zinc status.⁴⁵

Treatment—The recommended dose for zinc supplementation is 20 to 40 mg daily with higher doses (>50 mg/d) for patients with malabsorptive syndromes such as IBD.⁴⁶ It can be administered orally or parenterally. Although rare, zinc replacement therapy may be associated with diarrhea, nausea, vomiting, mild headaches, and fatigue.⁴⁶ Additional considerations should be taken when repleting other micronutrients with zinc, as calcium and folate can inhibit zinc reabsorption, while zinc itself can inhibit iron and copper reabsorption.⁴⁷

Vitamin D and Calcium

Low vitamin D levels (<50 nmol/L) and hypocalcemia (<8.8 mg/dL) are common in patients with IBD.^48,49

Pathophysiology—Vitamin D levels are maintained via 2 mechanisms. The first mechanism is through the skin, as keratinocytes produce 7-dehydrocholesterol after exposure to UV light, which is converted into previtamin D₃ and then thermally isomerizes into vitamin D₃. This vitamin D₃ is then transported to the liver on vitamin D–binding protein.⁵⁰ The second mechanism is through oral vitamin D₃ that is absorbed through vitamin D receptors in intestinal epithelium and transported to the liver, where it is hydroxylated into 25-hydroxyvitamin D (25[OH]D), then to the kidneys for hydroxylation to 1,25(OH)₂D for redistribution throughout the body.⁵⁰ This activated form of vitamin D regulates calcium absorption in the intestine, and optimal vitamin D levels are necessary to absorb calcium efficiently.⁵¹ Inflammation from IBD within the small intestine can downregulate vitamin D receptors, causing malabsorption and decreased serum vitamin D.⁵²

Vitamin D signaling also is vital to maintaining the tight junctions and adherens junctions of the intestinal epithelium. Weakening the permeability of the epithelium further exacerbates malabsorption and subsequent vitamin D deficiency.⁵² A meta-analysis of 27 studies including 8316 patients with IBD showed low vitamin D levels were associated with increased odds of disease activity (OR=1.53; 95% CI, 1.32-1.77), mucosal inflammation (OR=1.25; 95% CI, 1.06-1.47), and future clinical relapse (OR=1.23; 95% CI, 1.03-1.47) in patients with Crohn disease. The authors concluded that low levels of vitamin D could be used as a potential biomarker of inflammatory status in Crohn disease.⁵³

Vitamin D and calcium are further implicated in maintaining skeletal health,⁴⁷ while vitamin D specifically helps maintain intestinal homeostasis⁵⁴ and immune system modulation in the skin.⁵⁵

Cutaneous Manifestations—Vitamin D is thought to play crucial roles in skin differentiation and proliferation, cutaneous innate immunity, hair follicle cycling, photoprotection, and wound healing.⁵⁶ Vitamin D deficiency has been observed in a large range of cutaneous diseases including skin cancer, psoriasis, vitiligo, bullous pemphigoid, atopic dermatitis, and various types of alopecia.^56-59 It is unclear whether vitamin D deficiency facilitates these disease processes or is merely the consequence of a disrupted cutaneous surface with the inability to complete the first step in vitamin D processing. A 2014 meta-analysis of 290 prospective cohort studies and 172 randomized trials concluded that 25(OH)D deficiency was associated with ill health and did not find causal evidence for any specific disease, dermatologic or otherwise.⁶⁰ Calcium deficiency may cause epidermal changes including dry skin, coarse hair, and brittle nails.⁶¹

Diagnosis and Monitoring—The ECCO guidelines recommend obtaining serum 25(OH)D levels every 3 months in patients with IBD.⁶² Levels less than 75 nmol/L are considered deficient, and a value less than 30 nmol/L increases the risk for osteomalacia and nutritional rickets, constituting severe vitamin D deficiency.^63-65

An observational study of 325 patients with IBD showed a statistically significant negative correlation between serum vitamin D and fecal calprotectin (r=−0.19; P<.001), a stool-based marker for gut inflammation, supporting vitamin D as a potential biomarker in IBD.⁶⁶

Evaluation of calcium can be done through serum levels in patients with IBD.⁶⁷ Patients with IBD are at risk for hypoalbuminemia; therefore, consideration should be taken to ensure calcium levels are corrected, as approximately 50% of calcium is bound to albumin or other ions in the body,⁶⁸ which can be done by adjusting the calcium concentration by 0.02 mmol/L for every 1 g/L of albumin above or below 40 g/L. In the most critically ill patients, a direct ionized calcium blood level should be used instead because the previously mentioned correction calculations are inaccurate when albumin is critically low.⁶⁹

Treatment—The ECCO guidelines recommend calcium and vitamin D repletion of 500 to 1000 mg and 800 to 1000 U, respectively, in patients with IBD on systemic corticosteroids to prevent the negative effects of bone loss.⁶² Calcium repletion in patients with IBD who are not on systemic steroids are the same as for the general population.⁶⁵

Vitamin D repletion also may help decrease IBD activity. In a prospective study, 10,000 IU/d of vitamin D in 10 patients with IBD—adjusted over 12 weeks to a target of 100 to 125 nmol/L of serum 25(OH)D—showed a significant reduction in clinical Crohn activity (P=.019) over the study period.⁷⁰ In contrast, 2000 IU/d for 3 months in an RCT of 27 patients with Crohn disease found significantly lower CRP (P=.019) and significantly higher self-reported quality of life (P=.037) but nonsignificant decreases in Crohn activity (P=.082) in patients with 25(OH)D levels of 75 nmol/L or higher compared with those with 25(OH)D levels less than 75 nmol/L.⁷¹

These discrepancies illustrate the need for expanded clinical trials to elucidate the optimal vitamin D dosing for patients with IBD. Ultimately, assessing vitamin D and calcium status and considering repletion in patients with IBD, especially those with comorbid dermatologic diseases such as poor wound healing, psoriasis, or atopic dermatitis, is important.

Vitamin B₆ (Pyridoxine)

Pathophysiology—Pyridoxine is an important coenzyme for many functions including amino acid transamination, fatty acid metabolism, and conversion of tryptophan to niacin. It is absorbed in the jejunum and ileum and subsequently transported to the liver for rephosphorylation and release into its active form.³⁶ An observational study assessing the nutritional status of patients with IBD found that only 5.7% of 105 patients with food records had inadequate dietary intake of pyridoxine, but 29% of all patients with IBD had subnormal pyridoxine levels.⁷² Additionally, they found no significant difference in the prevalence of subnormal pyridoxine levels in patients with active IBD vs IBD in remission. The authors suggested that the subnormal pyridoxine levels in patients with IBD likely were multifactorial and resulted from malabsorption due to active disease, inflammation, and inadequate intake.⁷²

Cutaneous Manifestations—Cutaneous findings associated with pyridoxine deficiency include periorificial and perineal dermatitis,⁷³ angular stomatitis, and cheilitis with associated burning, redness, and tongue edema.³⁶ Additionally, pyridoxine is involved in the conversion of tryptophan to niacin, and its deficiency may manifest with pellagralike findings.⁷⁴

Because pyridoxine is critical to protein metabolism, its deficiency may disrupt key cellular structures that rely on protein concentrations to maintain structural integrity. One such structure in the skin that heavily relies on protein concentrations is the ground substance of the extracellular matrix—the amorphous gelatinous spaces that occupy the areas between the extracellular matrix, which consists of cross-linked glycosaminoglycans and proteins.⁷⁵ Without protein, ground substance increases in viscosity and can disrupt the epidermal barrier, leading to increased transepidermal water loss and ultimately inflammation.⁷⁶ Although this theory has yet to be validated fully, this is a potential mechanistic explanation for the inflammation in dermal papillae that leads to dermatitis observed in pyridoxine deficiency.

Diagnosis and Monitoring—Direct biomarkers of pyridoxine status are in serum, plasma, erythrocytes, and urine, with the most common measurement in plasma as pyridoxal 5′-phosphate (PLP).⁷⁷ Plasma PLP concentrations lower than 20 nmol/L are suggestive of deficiency.⁷⁸ Plasma PLP has shown inverse relationships with acute phase inflammatory markers CRP⁷⁹ and AP,⁷⁸ thereby raising concerns for its validity to assess pyridoxine status in patients with symptomatic IBD.⁸⁰

Alternative evaluations of pyridoxine include tryptophan and methionine loading tests,³⁶ which are measured via urinary excretion and require normal kidney function to be accurate. They should be considered in IBD if necessary, but routine testing, even in patients with symptomatic IBD, is not recommended in the ECCO guidelines. Additional considerations should be taken in patients with altered nutrient requirements such as those who have undergone bowel resection due to highly active disease or those who receive parenteral nutritional supplementation.⁸¹

Treatment—Recommendations for oral pyridoxine supplementation range from 25 to 600 mg daily,⁸² with symptoms typically improving on 100 mg daily.³⁶ Pyridoxine supplementation may have additional benefits for patients with IBD and potentially modulate disease severity. An IL-10 knockout mouse supplemented with pyridoxine had an approximately 60% reduction (P<.05) in inflammation compared to mice deficient in pyridoxine.⁸³ The authors suggest that PLP-dependent enzymes can inhibit further proinflammatory signaling and T-cell migration that can exacerbate IBD. Ultimately, more data is needed before determining the efficacy of pyridoxine supplementation for active IBD.

Vitamin B₁₂ and Vitamin B₉ (Folic Acid)

Pathophysiology—Vitamin B₁₂ is reabsorbed in the terminal ileum, the distal portion of the small intestine. The American Gastroenterological Association recommends that patients with a history of extensive ileal disease or prior ileal surgery, which is the case for many patients with Crohn disease, be monitored for vitamin B₁₂ deficiency.²³ Monitoring and rapid supplementation of vitamin B₁₂ can prevent pernicious anemia and irreversible neurologic damage that may result from deficiency.⁸⁴

Folic acid is primarily absorbed in the duodenum and jejunum of the small intestine. A meta-analysis performed in 2017 assessed studies observing folic acid and vitamin B₁₂ levels in 1086 patients with IBD compared with 1484 healthy controls and found an average difference in serum folate concentration of 0.46 nmol/L (P<.001).⁸⁴ Interestingly, this study did not find a significant difference in serum vitamin B₁₂ levels between patients with IBD and healthy controls, highlighting the mechanism of vitamin B₁₂ deficiency in IBD because only patients with terminal ileal involvement are at risk for malabsorption and subsequent deficiency.

Cutaneous Manifestations—Both vitamin B₁₂ and folic acid deficiency can manifest as cheilitis, glossitis, and/or generalized hyperpigmentation that is accentuated in the flexural areas, palms, soles, and oral cavity.^85,86 Systemic symptoms of patients with vitamin B₁₂ and folic acid deficiency include megaloblastic anemia, pallor, and fatigue. A potential mechanism for the hyperpigmentation observed from vitamin B₁₂ deficiency came from an electron microscope study that showed an increased concentration of melanosomes in a patient with deficiency.⁸⁷

Diagnosis and Monitoring—In patients with suspected vitamin B₁₂ and/or folic acid deficiency, initial evaluation should include a CBC with peripheral smear and serum vitamin B₁₂ and folate levels. In cases for which the diagnosis still is unclear after initial testing, methylmalonic acid and homocysteine levels can help differentiate between the 2 deficiencies. Methylmalonic acid classically is elevated (>260 nmol/L) in vitamin B₁₂ deficiency but not in folate deficiency.⁸⁸ Cut-off values for vitamin B₁₂ deficiency are less than 200 to 250 pg/mL forserum vitamin B₁₂ and/or an elevated level of methylmalonic acid (>0.271 µmol/L).⁸⁹ A serum folic acid value greater than 3 ng/mL and/or erythrocyte folate concentrations greater than 140 ng/mL are considered adequate, whereas an indicator of folic acid deficiency is a homocysteine level less than 10 µmol/L.⁹⁰ A CBC can screen for macrocytic megaloblastic anemias (mean corpuscular volume >100 fl), which are classic diagnostic signs of an underlying vitamin B₁₂ or folate deficiency.

Treatment—According to the Centers for Disease Control and Prevention, supplementation of vitamin B₁₂ can be done orally with 1000 µg daily in patients with deficiency. In patients with active IBD, oral reabsorption of vitamin B₁₂ can be less effective, making subcutaneous or intramuscular administration (1000 µg/wk for 8 weeks, then monthly for life) better options.⁸⁹

Patients with IBD managed with methotrexate should be screened carefully for folate deficiency. Methotrexate is a folate analog that sometimes is used for the treatment of IBD. Reversible competitive inhibition of dihydrofolate reductase can precipitate a systemic folic acid decrease.⁹¹ Typically, oral folic acid (1 to 5 mg/d) is sufficient to treat folate deficiency, with the ESPEN recommending 5 mg once weekly 24 to 72 hours after methotrexate treatment or 1 mg daily for 5 days per week in patients with IBD.¹ Alternative formulations—IV, subcutaneous, or intramuscular—are available for patients who cannot tolerate oral intake.⁹²

Final Thoughts

Dermatologists can be the first to observe the cutaneous manifestations of micronutrient deficiencies. Although the symptoms of each micronutrient deficiency discussed may overlap, attention to small clinical clues in patients with IBD can improve patient outcomes and quality of life. For example, koilonychia with glossitis and xerosis likely is due to iron deficiency, while zinc deficiency should be suspected in patients with scaly eczematous plaques in skin folds. A high level of suspicion for micronutrient deficiencies in patients with IBD should be followed by a complete patient history, review of systems, and thorough clinical examination. A thorough laboratory evaluation can pinpoint nutritional deficiencies in patients with IBD, keeping in mind that specific biomarkers such as ferritin and serum zinc also act as acute phase reactants and should be interpreted in this context. Co-management with gastroenterologists should be a priority in patients with IBD, as gaining control of inflammatory disease is crucial for the prevention of recurrent vitamin and micronutrient deficiencies in addition to long-term health in this population.

In 2023, ESPEN (the European Society for Clinical Nutrition and Metabolism) published consensus recommendations highlighting the importance of regular monitoring and treatment of nutrient deficiencies in patients with inflammatory bowel disease (IBD) for improved prognosis, mortality, and quality of life.¹ Suboptimal nutrition in patients with IBD predominantly results from inflammation of the gastrointestinal (GI) tract leading to malabsorption; however, medications commonly used to manage IBD also can contribute to malnutrition.^2,3 Additionally, patients may develop nausea and food avoidance due to medication or the disease itself, leading to nutritional withdrawal and eventual deficiency.⁴ Even with the development of diets focused on balancing nutritional needs and decreasing inflammation,⁵ offsetting this aversion to food can be difficult to overcome.²

Cutaneous manifestations of IBD are multifaceted and can be secondary to the disease, reactive to or associated with IBD, or effects from nutritional deficiencies. The most common vitamin and nutrient deficiencies in patients with IBD include iron; zinc; calcium; vitamin D; and vitamins B₆ (pyridoxine), B₉ (folic acid), and B₁₂.⁶ Malnutrition may manifest with cutaneous disease, and dermatologists can be the first to identify and assess for nutritional deficiencies. In this article, we review the mechanisms of these micronutrient depletions in the context of IBD, their subsequent dermatologic manifestations (Table), and treatment and monitoring guidelines for each deficiency.

Iron

A systematic review conducted from 2007 to 2012 in European patients with IBD (N=2192) found the overall prevalence of anemia in this population to be 24% (95% CI, 18%-31%), with 57% of patients with anemia experiencing iron deficiency.⁷ Anemia is observed more commonly in patients hospitalized with IBD and is common in patients with both Crohn disease and ulcerative colitis.⁸

Pathophysiology—Iron is critically important in oxygen transportation throughout the body as a major component of hemoglobin. Physiologically, the low pH of the duodenum and proximal jejunum allows divalent metal transporter 1 to transfer dietary Fe³⁺ into enterocytes, where it is reduced to the transportable Fe²⁺.^9,10 Distribution of Fe²⁺ ions from enterocytes relies on ferroportin, an iron-transporting protein, which is heavily regulated by the protein hepcidin.¹¹ Hepcidin, a known acute phase reactant, will increase in the setting of active IBD, causing a depletion of ferroportin and an inability of the body to utilize the stored iron in enterocytes.¹² This poor utilization of iron stores combined with blood loss caused by inflammation in the GI tract is the proposed primary mechanism of iron-deficiency anemia observed in patients with IBD.¹³

Cutaneous Manifestations—From a dermatologic perspective, iron-deficiency anemia can manifest with a wide range of symptoms including glossitis, koilonychia, xerosis and/or pruritus, and brittle hair or hair loss.^14,15 Although the underlying pathophysiology of these cutaneous manifestations is not fully understood, there are several theories assessing the mechanisms behind the skin findings of iron deficiency.

Atrophic glossitis has been observed in many patients with iron deficiency and is thought to manifest due to low iron concentrations in the blood, thereby decreasing oxygen delivery to the papillae of the dorsal tongue with resultant atrophy.^16,17 Similarly, decreased oxygen delivery to the nail bed capillaries may cause deformities in the nail called koilonychia (or “spoon nails”).¹⁸ Iron is a key co-factor in collagen lysyl hydroxylase that promotes collagen binding; iron deficiency may lead to disruptions in the epidermal barrier that can cause pruritus and xerosis.¹⁹ An observational study of 200 healthy patients with a primary concern of pruritus found a correlation between low serum ferritin and a higher degree of pruritus (r=−0.768; P<.00001).²⁰

Evidence for iron’s role in hair growth comes from a mouse model study with a mutation in the serine protease TMPRSS6—a protein that regulates hepcidin and iron absorption—which caused an increase in hepcidin production and subsequent systemic iron deficiency. Mice at 4 weeks of age were devoid of all body hair but had substantial regrowth after initiation of a 2-week iron-rich diet, which suggests a connection between iron repletion and hair growth in mice with iron deficiency.²¹ Additionally, a meta-analysis analyzing the comorbidities of patients with alopecia areata found them to have higher odds (odds ratio [OR]=2.78; 95% CI, 1.23-6.29) of iron-deficiency anemia but no association with IBD (OR=1.48; 95% CI, 0.32-6.82).²²

Diagnosis and Monitoring—The American Gastroenterological Association recommends a complete blood cell count (CBC), serum ferritin, transferrin saturation (TfS), and C-reactive protein (CRP) as standard evaluations for iron deficiency in patients with IBD. Patients with active IBD should be screened every 3 months,and patients with inactive disease should be screened every 6 to 12 months.²³

Although ferritin and TfS often are used as markers for iron status in healthy individuals, they are positive and negative acute phase reactants, respectively. Using them to assess iron status in patients with IBD may inaccurately represent iron status in the setting of inflammation from the disease.²⁴ The European Crohn’s and Colitis Organisation (ECCO) produced guidelines to define iron deficiency as a TfS less than 20% or a ferritin level less than 30 µg/L in patients without evidence of active IBD and a ferritin level less than 100 µg/L for patients with active inflammation.²⁵

A 2020 multicenter observational study of 202 patients with diagnosed IBD found that the ECCO guideline of ferritin less than 30 µg/L had an area under the receiver operating characteristic (AUROC) curve of 0.69, a sensitivity of 0.43, and a specificity of 0.95 in their population.²⁶ In a sensitivity analysis stratifying patients by CRP level (<10 or ≥10 mg/L), the authors found that for patients with ulcerative colitis and a CRP less than 10 mg/L, a cut-off value of ferritin less than 65 µg/L (AUROC=0.78) had a sensitivity of 0.78 and specificity of 0.76, and a TfS value of less than 16% (AUROC=0.88) had a sensitivity of 0.79 and a specificity of 0.9. In patients with a CRP of 10 mg/L or greater, a cut-off value of ferritin 80 µg/L (AUROC=0.76) had a sensitivity of 0.75 and a specificity of 0.82, and a TfS value of less than 11% (AUROC=0.69) had a sensitivity of 0.79 and a specificity of 0.88. There were no ferritin cut-off values associated with good diagnostic performance (defined as both sensitivity and specificity >0.70) for iron deficiency in patients with Crohn disease.²⁶

The authors recommended using an alternative iron measurement such as soluble transferrin receptor (sTfR)/log ferritin ratio (TfR-F) that is not influenced by active inflammation and has a good correlation with ferritin values (TfR-F: r=0.66; P<.001).²⁶ However, both sTfR and TfR-F have high costs and intermethod variability as well as differences in their reference ranges depending on which laboratory performs the analysis, limiting the accessibility and practicality of easily obtaining these tests.²⁷ Although there may be inaccuracies for standard ferritin or TfS under ECCO guidelines, proposed alternatives have their own limitations, which may make ferritin and TfS the most reasonable evaluations of iron status as long as disease activity status at the time of testing is taken into consideration.

Treatment—Treatment of underlying iron deficiency in patients with IBD requires reversing the cause of the deficiency and supplementing iron. In patients with IBD, the options to supplement iron may be limited by active disease, making oral intake less effective. Oral iron supplementation also is associated with notable GI adverse effects that may be exacerbated in patients with IBD. A systematic review of 43 randomized controlled trials (RCTs) evaluating GI adverse effects (eg, nausea, abdominal pain, diarrhea, constipation, and black or tarry stools) of oral ferrous sulfate compared with placebo or intravenous (IV) iron supplementation in healthy nonanemic individuals found a significant increase in GI adverse effects with oral supplementation (placebo: OR=2.32; P<.0001; IV: OR=3.05; P<.0001).²⁸

Therefore, IV iron repletion may be necessary in patients with IBD and may require numerous infusions depending on the formulation of iron. In an RCT conducted in 2011, patients with iron-deficiency anemia with quiescent or mild to moderate IBD were treated with either IV iron sulfate or ferric carboxymaltose.²⁹ With a primary end point of hemoglobin response greater than 2 g/dL, the authors found that 150 of 240 patients responded to ferric carboxymaltose vs 118 of 235 treated with iron sulfate (P=.004). The dosing for ferric carboxymaltose was 1 to 3 infusions of 500 to 1000 mg of iron and for iron sulfate up to 11 infusions of 200 mg of iron.²⁹

Zinc

A systematic review of zinc deficiency in patients with IBD identified 7 studies including 2413 patients and revealed those with Crohn disease had a higher prevalence of zinc deficiency compared with patients with ulcerative colitis (54% vs 41%).³⁰

Pathophysiology—Zinc serves as a catalytic cofactor for enzymatic activity within proteins and immune cells.³¹ The homeostasis of zinc is tightly regulated within the brush border of the small intestine by zinc transporters ZIP4 and ZIP1 from the lumen of enterocytes into the bloodstream.³² Inflammation in the small intestine due to Crohn disease can result in zinc malabsorption.

Ranaldi et al³³ exposed intestinal cells and zinc-depleted intestinal cells to tumor necrosis factor α media to simulate an inflammatory environment. They measured transepithelial electrical resistance as a surrogate for transmembrane permeability and found that zinc-depleted cells had a statistically significantly higher transepithelial electrical resistance percentage (60% reduction after 4 hours; P<1.10^–6) when exposed to tumor necrosis factor α signaling compared with normal intestinal cells. They concluded that zinc deficiency can increase intestinal permeability in the presence of inflammation, creating a cycle of further nutrient malabsorption and inflammation exacerbating IBD symptoms.³³

Cutaneous Manifestations—After absorption in the small intestine, approximately 5% of zinc resides in the skin, with the highest concentration in the stratum spinosum.³⁴ A cell study found that keratinocytes in zinc-deficient environments had higher rates of apoptosis compared with cells in normal media. The authors proposed that this higher rate of apoptosis and the resulting inflammation could be a mechanism for developing the desquamative or eczematous scaly plaques that are common cutaneous manifestations of zinc deficiency.³⁵

Other cutaneous findings may include angular cheilitis, stomatitis, glossitis, paronychia, onychodystrophy, generalized alopecia, and delayed wound healing.³⁶ The histopathology of these skin lesions is characterized by granular layer loss, epidermal pallor, confluent parakeratosis, spongiosis, dyskeratosis, and psoriasiform hyperplasia.³⁷

Diagnosis and Monitoring—Assessing serum zinc levels is challenging, as they may decrease during states of inflammation.³⁸ A mouse model study showed a 3.1-fold increase (P<.001) in ZIP14 expression in wild-type mice compared with an IL-6 -/- knock-down model after IL-6 exposure. The authors concluded that the upregulation of ZIP14 in the liver due to inflammatory cytokine upregulation decreases zinc availability in serum.³⁹ Additionally, serum zinc can overestimate the level of deficiency in IBD because approximately 75% of serum zinc is bound to albumin, which decreases in the setting of inflammation.^40-42

Alternatively, alkaline phosphatase (AP), a zinc-dependent metalloenzyme, may be a better evaluator of zinc status during periods of inflammation. A study in rats evaluated zinc through serum zinc levels and AP levels after a period of induced stress to mimic a short-term inflammatory state.⁴³ The researchers found that total body stores of zinc were unaffected throughout the experiment; only serum zinc declined throughout the experiment duration while AP did not. Because approximately 75% of serum zinc is bound to serum albumin,⁴² the researchers concluded the induced inflammatory state depleted serum albumin and redistributed zinc to the liver, causing the observed serum zinc changes, while total body zinc levels and AP were largely unaffected in comparison.⁴³ Comorbid conditions such as liver or bone disease can increase AP levels, which limits the utility of AP as a surrogate for zinc in patients with comorbidities.⁴⁴ However, even in the context of active IBD, serum zinc still is currently considered the best biomarker to evaluate zinc status.⁴⁵

Treatment—The recommended dose for zinc supplementation is 20 to 40 mg daily with higher doses (>50 mg/d) for patients with malabsorptive syndromes such as IBD.⁴⁶ It can be administered orally or parenterally. Although rare, zinc replacement therapy may be associated with diarrhea, nausea, vomiting, mild headaches, and fatigue.⁴⁶ Additional considerations should be taken when repleting other micronutrients with zinc, as calcium and folate can inhibit zinc reabsorption, while zinc itself can inhibit iron and copper reabsorption.⁴⁷

Vitamin D and Calcium

Low vitamin D levels (<50 nmol/L) and hypocalcemia (<8.8 mg/dL) are common in patients with IBD.^48,49

Pathophysiology—Vitamin D levels are maintained via 2 mechanisms. The first mechanism is through the skin, as keratinocytes produce 7-dehydrocholesterol after exposure to UV light, which is converted into previtamin D₃ and then thermally isomerizes into vitamin D₃. This vitamin D₃ is then transported to the liver on vitamin D–binding protein.⁵⁰ The second mechanism is through oral vitamin D₃ that is absorbed through vitamin D receptors in intestinal epithelium and transported to the liver, where it is hydroxylated into 25-hydroxyvitamin D (25[OH]D), then to the kidneys for hydroxylation to 1,25(OH)₂D for redistribution throughout the body.⁵⁰ This activated form of vitamin D regulates calcium absorption in the intestine, and optimal vitamin D levels are necessary to absorb calcium efficiently.⁵¹ Inflammation from IBD within the small intestine can downregulate vitamin D receptors, causing malabsorption and decreased serum vitamin D.⁵²

Vitamin D signaling also is vital to maintaining the tight junctions and adherens junctions of the intestinal epithelium. Weakening the permeability of the epithelium further exacerbates malabsorption and subsequent vitamin D deficiency.⁵² A meta-analysis of 27 studies including 8316 patients with IBD showed low vitamin D levels were associated with increased odds of disease activity (OR=1.53; 95% CI, 1.32-1.77), mucosal inflammation (OR=1.25; 95% CI, 1.06-1.47), and future clinical relapse (OR=1.23; 95% CI, 1.03-1.47) in patients with Crohn disease. The authors concluded that low levels of vitamin D could be used as a potential biomarker of inflammatory status in Crohn disease.⁵³

Vitamin D and calcium are further implicated in maintaining skeletal health,⁴⁷ while vitamin D specifically helps maintain intestinal homeostasis⁵⁴ and immune system modulation in the skin.⁵⁵

Cutaneous Manifestations—Vitamin D is thought to play crucial roles in skin differentiation and proliferation, cutaneous innate immunity, hair follicle cycling, photoprotection, and wound healing.⁵⁶ Vitamin D deficiency has been observed in a large range of cutaneous diseases including skin cancer, psoriasis, vitiligo, bullous pemphigoid, atopic dermatitis, and various types of alopecia.^56-59 It is unclear whether vitamin D deficiency facilitates these disease processes or is merely the consequence of a disrupted cutaneous surface with the inability to complete the first step in vitamin D processing. A 2014 meta-analysis of 290 prospective cohort studies and 172 randomized trials concluded that 25(OH)D deficiency was associated with ill health and did not find causal evidence for any specific disease, dermatologic or otherwise.⁶⁰ Calcium deficiency may cause epidermal changes including dry skin, coarse hair, and brittle nails.⁶¹

Diagnosis and Monitoring—The ECCO guidelines recommend obtaining serum 25(OH)D levels every 3 months in patients with IBD.⁶² Levels less than 75 nmol/L are considered deficient, and a value less than 30 nmol/L increases the risk for osteomalacia and nutritional rickets, constituting severe vitamin D deficiency.^63-65

An observational study of 325 patients with IBD showed a statistically significant negative correlation between serum vitamin D and fecal calprotectin (r=−0.19; P<.001), a stool-based marker for gut inflammation, supporting vitamin D as a potential biomarker in IBD.⁶⁶

Evaluation of calcium can be done through serum levels in patients with IBD.⁶⁷ Patients with IBD are at risk for hypoalbuminemia; therefore, consideration should be taken to ensure calcium levels are corrected, as approximately 50% of calcium is bound to albumin or other ions in the body,⁶⁸ which can be done by adjusting the calcium concentration by 0.02 mmol/L for every 1 g/L of albumin above or below 40 g/L. In the most critically ill patients, a direct ionized calcium blood level should be used instead because the previously mentioned correction calculations are inaccurate when albumin is critically low.⁶⁹

Treatment—The ECCO guidelines recommend calcium and vitamin D repletion of 500 to 1000 mg and 800 to 1000 U, respectively, in patients with IBD on systemic corticosteroids to prevent the negative effects of bone loss.⁶² Calcium repletion in patients with IBD who are not on systemic steroids are the same as for the general population.⁶⁵

Vitamin D repletion also may help decrease IBD activity. In a prospective study, 10,000 IU/d of vitamin D in 10 patients with IBD—adjusted over 12 weeks to a target of 100 to 125 nmol/L of serum 25(OH)D—showed a significant reduction in clinical Crohn activity (P=.019) over the study period.⁷⁰ In contrast, 2000 IU/d for 3 months in an RCT of 27 patients with Crohn disease found significantly lower CRP (P=.019) and significantly higher self-reported quality of life (P=.037) but nonsignificant decreases in Crohn activity (P=.082) in patients with 25(OH)D levels of 75 nmol/L or higher compared with those with 25(OH)D levels less than 75 nmol/L.⁷¹

These discrepancies illustrate the need for expanded clinical trials to elucidate the optimal vitamin D dosing for patients with IBD. Ultimately, assessing vitamin D and calcium status and considering repletion in patients with IBD, especially those with comorbid dermatologic diseases such as poor wound healing, psoriasis, or atopic dermatitis, is important.

Vitamin B₆ (Pyridoxine)

Pathophysiology—Pyridoxine is an important coenzyme for many functions including amino acid transamination, fatty acid metabolism, and conversion of tryptophan to niacin. It is absorbed in the jejunum and ileum and subsequently transported to the liver for rephosphorylation and release into its active form.³⁶ An observational study assessing the nutritional status of patients with IBD found that only 5.7% of 105 patients with food records had inadequate dietary intake of pyridoxine, but 29% of all patients with IBD had subnormal pyridoxine levels.⁷² Additionally, they found no significant difference in the prevalence of subnormal pyridoxine levels in patients with active IBD vs IBD in remission. The authors suggested that the subnormal pyridoxine levels in patients with IBD likely were multifactorial and resulted from malabsorption due to active disease, inflammation, and inadequate intake.⁷²

Cutaneous Manifestations—Cutaneous findings associated with pyridoxine deficiency include periorificial and perineal dermatitis,⁷³ angular stomatitis, and cheilitis with associated burning, redness, and tongue edema.³⁶ Additionally, pyridoxine is involved in the conversion of tryptophan to niacin, and its deficiency may manifest with pellagralike findings.⁷⁴

Because pyridoxine is critical to protein metabolism, its deficiency may disrupt key cellular structures that rely on protein concentrations to maintain structural integrity. One such structure in the skin that heavily relies on protein concentrations is the ground substance of the extracellular matrix—the amorphous gelatinous spaces that occupy the areas between the extracellular matrix, which consists of cross-linked glycosaminoglycans and proteins.⁷⁵ Without protein, ground substance increases in viscosity and can disrupt the epidermal barrier, leading to increased transepidermal water loss and ultimately inflammation.⁷⁶ Although this theory has yet to be validated fully, this is a potential mechanistic explanation for the inflammation in dermal papillae that leads to dermatitis observed in pyridoxine deficiency.

Diagnosis and Monitoring—Direct biomarkers of pyridoxine status are in serum, plasma, erythrocytes, and urine, with the most common measurement in plasma as pyridoxal 5′-phosphate (PLP).⁷⁷ Plasma PLP concentrations lower than 20 nmol/L are suggestive of deficiency.⁷⁸ Plasma PLP has shown inverse relationships with acute phase inflammatory markers CRP⁷⁹ and AP,⁷⁸ thereby raising concerns for its validity to assess pyridoxine status in patients with symptomatic IBD.⁸⁰

Alternative evaluations of pyridoxine include tryptophan and methionine loading tests,³⁶ which are measured via urinary excretion and require normal kidney function to be accurate. They should be considered in IBD if necessary, but routine testing, even in patients with symptomatic IBD, is not recommended in the ECCO guidelines. Additional considerations should be taken in patients with altered nutrient requirements such as those who have undergone bowel resection due to highly active disease or those who receive parenteral nutritional supplementation.⁸¹

Treatment—Recommendations for oral pyridoxine supplementation range from 25 to 600 mg daily,⁸² with symptoms typically improving on 100 mg daily.³⁶ Pyridoxine supplementation may have additional benefits for patients with IBD and potentially modulate disease severity. An IL-10 knockout mouse supplemented with pyridoxine had an approximately 60% reduction (P<.05) in inflammation compared to mice deficient in pyridoxine.⁸³ The authors suggest that PLP-dependent enzymes can inhibit further proinflammatory signaling and T-cell migration that can exacerbate IBD. Ultimately, more data is needed before determining the efficacy of pyridoxine supplementation for active IBD.

Vitamin B₁₂ and Vitamin B₉ (Folic Acid)

Pathophysiology—Vitamin B₁₂ is reabsorbed in the terminal ileum, the distal portion of the small intestine. The American Gastroenterological Association recommends that patients with a history of extensive ileal disease or prior ileal surgery, which is the case for many patients with Crohn disease, be monitored for vitamin B₁₂ deficiency.²³ Monitoring and rapid supplementation of vitamin B₁₂ can prevent pernicious anemia and irreversible neurologic damage that may result from deficiency.⁸⁴

Folic acid is primarily absorbed in the duodenum and jejunum of the small intestine. A meta-analysis performed in 2017 assessed studies observing folic acid and vitamin B₁₂ levels in 1086 patients with IBD compared with 1484 healthy controls and found an average difference in serum folate concentration of 0.46 nmol/L (P<.001).⁸⁴ Interestingly, this study did not find a significant difference in serum vitamin B₁₂ levels between patients with IBD and healthy controls, highlighting the mechanism of vitamin B₁₂ deficiency in IBD because only patients with terminal ileal involvement are at risk for malabsorption and subsequent deficiency.

Cutaneous Manifestations—Both vitamin B₁₂ and folic acid deficiency can manifest as cheilitis, glossitis, and/or generalized hyperpigmentation that is accentuated in the flexural areas, palms, soles, and oral cavity.^85,86 Systemic symptoms of patients with vitamin B₁₂ and folic acid deficiency include megaloblastic anemia, pallor, and fatigue. A potential mechanism for the hyperpigmentation observed from vitamin B₁₂ deficiency came from an electron microscope study that showed an increased concentration of melanosomes in a patient with deficiency.⁸⁷

Diagnosis and Monitoring—In patients with suspected vitamin B₁₂ and/or folic acid deficiency, initial evaluation should include a CBC with peripheral smear and serum vitamin B₁₂ and folate levels. In cases for which the diagnosis still is unclear after initial testing, methylmalonic acid and homocysteine levels can help differentiate between the 2 deficiencies. Methylmalonic acid classically is elevated (>260 nmol/L) in vitamin B₁₂ deficiency but not in folate deficiency.⁸⁸ Cut-off values for vitamin B₁₂ deficiency are less than 200 to 250 pg/mL forserum vitamin B₁₂ and/or an elevated level of methylmalonic acid (>0.271 µmol/L).⁸⁹ A serum folic acid value greater than 3 ng/mL and/or erythrocyte folate concentrations greater than 140 ng/mL are considered adequate, whereas an indicator of folic acid deficiency is a homocysteine level less than 10 µmol/L.⁹⁰ A CBC can screen for macrocytic megaloblastic anemias (mean corpuscular volume >100 fl), which are classic diagnostic signs of an underlying vitamin B₁₂ or folate deficiency.

Treatment—According to the Centers for Disease Control and Prevention, supplementation of vitamin B₁₂ can be done orally with 1000 µg daily in patients with deficiency. In patients with active IBD, oral reabsorption of vitamin B₁₂ can be less effective, making subcutaneous or intramuscular administration (1000 µg/wk for 8 weeks, then monthly for life) better options.⁸⁹

Patients with IBD managed with methotrexate should be screened carefully for folate deficiency. Methotrexate is a folate analog that sometimes is used for the treatment of IBD. Reversible competitive inhibition of dihydrofolate reductase can precipitate a systemic folic acid decrease.⁹¹ Typically, oral folic acid (1 to 5 mg/d) is sufficient to treat folate deficiency, with the ESPEN recommending 5 mg once weekly 24 to 72 hours after methotrexate treatment or 1 mg daily for 5 days per week in patients with IBD.¹ Alternative formulations—IV, subcutaneous, or intramuscular—are available for patients who cannot tolerate oral intake.⁹²

Final Thoughts

Dermatologists can be the first to observe the cutaneous manifestations of micronutrient deficiencies. Although the symptoms of each micronutrient deficiency discussed may overlap, attention to small clinical clues in patients with IBD can improve patient outcomes and quality of life. For example, koilonychia with glossitis and xerosis likely is due to iron deficiency, while zinc deficiency should be suspected in patients with scaly eczematous plaques in skin folds. A high level of suspicion for micronutrient deficiencies in patients with IBD should be followed by a complete patient history, review of systems, and thorough clinical examination. A thorough laboratory evaluation can pinpoint nutritional deficiencies in patients with IBD, keeping in mind that specific biomarkers such as ferritin and serum zinc also act as acute phase reactants and should be interpreted in this context. Co-management with gastroenterologists should be a priority in patients with IBD, as gaining control of inflammatory disease is crucial for the prevention of recurrent vitamin and micronutrient deficiencies in addition to long-term health in this population.

In 2023, ESPEN (the European Society for Clinical Nutrition and Metabolism) published consensus recommendations highlighting the importance of regular monitoring and treatment of nutrient deficiencies in patients with inflammatory bowel disease (IBD) for improved prognosis, mortality, and quality of life.¹ Suboptimal nutrition in patients with IBD predominantly results from inflammation of the gastrointestinal (GI) tract leading to malabsorption; however, medications commonly used to manage IBD also can contribute to malnutrition.^2,3 Additionally, patients may develop nausea and food avoidance due to medication or the disease itself, leading to nutritional withdrawal and eventual deficiency.⁴ Even with the development of diets focused on balancing nutritional needs and decreasing inflammation,⁵ offsetting this aversion to food can be difficult to overcome.²

Cutaneous manifestations of IBD are multifaceted and can be secondary to the disease, reactive to or associated with IBD, or effects from nutritional deficiencies. The most common vitamin and nutrient deficiencies in patients with IBD include iron; zinc; calcium; vitamin D; and vitamins B₆ (pyridoxine), B₉ (folic acid), and B₁₂.⁶ Malnutrition may manifest with cutaneous disease, and dermatologists can be the first to identify and assess for nutritional deficiencies. In this article, we review the mechanisms of these micronutrient depletions in the context of IBD, their subsequent dermatologic manifestations (Table), and treatment and monitoring guidelines for each deficiency.

Iron

A systematic review conducted from 2007 to 2012 in European patients with IBD (N=2192) found the overall prevalence of anemia in this population to be 24% (95% CI, 18%-31%), with 57% of patients with anemia experiencing iron deficiency.⁷ Anemia is observed more commonly in patients hospitalized with IBD and is common in patients with both Crohn disease and ulcerative colitis.⁸

Pathophysiology—Iron is critically important in oxygen transportation throughout the body as a major component of hemoglobin. Physiologically, the low pH of the duodenum and proximal jejunum allows divalent metal transporter 1 to transfer dietary Fe³⁺ into enterocytes, where it is reduced to the transportable Fe²⁺.^9,10 Distribution of Fe²⁺ ions from enterocytes relies on ferroportin, an iron-transporting protein, which is heavily regulated by the protein hepcidin.¹¹ Hepcidin, a known acute phase reactant, will increase in the setting of active IBD, causing a depletion of ferroportin and an inability of the body to utilize the stored iron in enterocytes.¹² This poor utilization of iron stores combined with blood loss caused by inflammation in the GI tract is the proposed primary mechanism of iron-deficiency anemia observed in patients with IBD.¹³

Cutaneous Manifestations—From a dermatologic perspective, iron-deficiency anemia can manifest with a wide range of symptoms including glossitis, koilonychia, xerosis and/or pruritus, and brittle hair or hair loss.^14,15 Although the underlying pathophysiology of these cutaneous manifestations is not fully understood, there are several theories assessing the mechanisms behind the skin findings of iron deficiency.

Atrophic glossitis has been observed in many patients with iron deficiency and is thought to manifest due to low iron concentrations in the blood, thereby decreasing oxygen delivery to the papillae of the dorsal tongue with resultant atrophy.^16,17 Similarly, decreased oxygen delivery to the nail bed capillaries may cause deformities in the nail called koilonychia (or “spoon nails”).¹⁸ Iron is a key co-factor in collagen lysyl hydroxylase that promotes collagen binding; iron deficiency may lead to disruptions in the epidermal barrier that can cause pruritus and xerosis.¹⁹ An observational study of 200 healthy patients with a primary concern of pruritus found a correlation between low serum ferritin and a higher degree of pruritus (r=−0.768; P<.00001).²⁰

Evidence for iron’s role in hair growth comes from a mouse model study with a mutation in the serine protease TMPRSS6—a protein that regulates hepcidin and iron absorption—which caused an increase in hepcidin production and subsequent systemic iron deficiency. Mice at 4 weeks of age were devoid of all body hair but had substantial regrowth after initiation of a 2-week iron-rich diet, which suggests a connection between iron repletion and hair growth in mice with iron deficiency.²¹ Additionally, a meta-analysis analyzing the comorbidities of patients with alopecia areata found them to have higher odds (odds ratio [OR]=2.78; 95% CI, 1.23-6.29) of iron-deficiency anemia but no association with IBD (OR=1.48; 95% CI, 0.32-6.82).²²

Diagnosis and Monitoring—The American Gastroenterological Association recommends a complete blood cell count (CBC), serum ferritin, transferrin saturation (TfS), and C-reactive protein (CRP) as standard evaluations for iron deficiency in patients with IBD. Patients with active IBD should be screened every 3 months,and patients with inactive disease should be screened every 6 to 12 months.²³

Although ferritin and TfS often are used as markers for iron status in healthy individuals, they are positive and negative acute phase reactants, respectively. Using them to assess iron status in patients with IBD may inaccurately represent iron status in the setting of inflammation from the disease.²⁴ The European Crohn’s and Colitis Organisation (ECCO) produced guidelines to define iron deficiency as a TfS less than 20% or a ferritin level less than 30 µg/L in patients without evidence of active IBD and a ferritin level less than 100 µg/L for patients with active inflammation.²⁵

A 2020 multicenter observational study of 202 patients with diagnosed IBD found that the ECCO guideline of ferritin less than 30 µg/L had an area under the receiver operating characteristic (AUROC) curve of 0.69, a sensitivity of 0.43, and a specificity of 0.95 in their population.²⁶ In a sensitivity analysis stratifying patients by CRP level (<10 or ≥10 mg/L), the authors found that for patients with ulcerative colitis and a CRP less than 10 mg/L, a cut-off value of ferritin less than 65 µg/L (AUROC=0.78) had a sensitivity of 0.78 and specificity of 0.76, and a TfS value of less than 16% (AUROC=0.88) had a sensitivity of 0.79 and a specificity of 0.9. In patients with a CRP of 10 mg/L or greater, a cut-off value of ferritin 80 µg/L (AUROC=0.76) had a sensitivity of 0.75 and a specificity of 0.82, and a TfS value of less than 11% (AUROC=0.69) had a sensitivity of 0.79 and a specificity of 0.88. There were no ferritin cut-off values associated with good diagnostic performance (defined as both sensitivity and specificity >0.70) for iron deficiency in patients with Crohn disease.²⁶

The authors recommended using an alternative iron measurement such as soluble transferrin receptor (sTfR)/log ferritin ratio (TfR-F) that is not influenced by active inflammation and has a good correlation with ferritin values (TfR-F: r=0.66; P<.001).²⁶ However, both sTfR and TfR-F have high costs and intermethod variability as well as differences in their reference ranges depending on which laboratory performs the analysis, limiting the accessibility and practicality of easily obtaining these tests.²⁷ Although there may be inaccuracies for standard ferritin or TfS under ECCO guidelines, proposed alternatives have their own limitations, which may make ferritin and TfS the most reasonable evaluations of iron status as long as disease activity status at the time of testing is taken into consideration.

Treatment—Treatment of underlying iron deficiency in patients with IBD requires reversing the cause of the deficiency and supplementing iron. In patients with IBD, the options to supplement iron may be limited by active disease, making oral intake less effective. Oral iron supplementation also is associated with notable GI adverse effects that may be exacerbated in patients with IBD. A systematic review of 43 randomized controlled trials (RCTs) evaluating GI adverse effects (eg, nausea, abdominal pain, diarrhea, constipation, and black or tarry stools) of oral ferrous sulfate compared with placebo or intravenous (IV) iron supplementation in healthy nonanemic individuals found a significant increase in GI adverse effects with oral supplementation (placebo: OR=2.32; P<.0001; IV: OR=3.05; P<.0001).²⁸

Therefore, IV iron repletion may be necessary in patients with IBD and may require numerous infusions depending on the formulation of iron. In an RCT conducted in 2011, patients with iron-deficiency anemia with quiescent or mild to moderate IBD were treated with either IV iron sulfate or ferric carboxymaltose.²⁹ With a primary end point of hemoglobin response greater than 2 g/dL, the authors found that 150 of 240 patients responded to ferric carboxymaltose vs 118 of 235 treated with iron sulfate (P=.004). The dosing for ferric carboxymaltose was 1 to 3 infusions of 500 to 1000 mg of iron and for iron sulfate up to 11 infusions of 200 mg of iron.²⁹

Zinc

A systematic review of zinc deficiency in patients with IBD identified 7 studies including 2413 patients and revealed those with Crohn disease had a higher prevalence of zinc deficiency compared with patients with ulcerative colitis (54% vs 41%).³⁰

Pathophysiology—Zinc serves as a catalytic cofactor for enzymatic activity within proteins and immune cells.³¹ The homeostasis of zinc is tightly regulated within the brush border of the small intestine by zinc transporters ZIP4 and ZIP1 from the lumen of enterocytes into the bloodstream.³² Inflammation in the small intestine due to Crohn disease can result in zinc malabsorption.

Ranaldi et al³³ exposed intestinal cells and zinc-depleted intestinal cells to tumor necrosis factor α media to simulate an inflammatory environment. They measured transepithelial electrical resistance as a surrogate for transmembrane permeability and found that zinc-depleted cells had a statistically significantly higher transepithelial electrical resistance percentage (60% reduction after 4 hours; P<1.10^–6) when exposed to tumor necrosis factor α signaling compared with normal intestinal cells. They concluded that zinc deficiency can increase intestinal permeability in the presence of inflammation, creating a cycle of further nutrient malabsorption and inflammation exacerbating IBD symptoms.³³

Cutaneous Manifestations—After absorption in the small intestine, approximately 5% of zinc resides in the skin, with the highest concentration in the stratum spinosum.³⁴ A cell study found that keratinocytes in zinc-deficient environments had higher rates of apoptosis compared with cells in normal media. The authors proposed that this higher rate of apoptosis and the resulting inflammation could be a mechanism for developing the desquamative or eczematous scaly plaques that are common cutaneous manifestations of zinc deficiency.³⁵

Other cutaneous findings may include angular cheilitis, stomatitis, glossitis, paronychia, onychodystrophy, generalized alopecia, and delayed wound healing.³⁶ The histopathology of these skin lesions is characterized by granular layer loss, epidermal pallor, confluent parakeratosis, spongiosis, dyskeratosis, and psoriasiform hyperplasia.³⁷

Diagnosis and Monitoring—Assessing serum zinc levels is challenging, as they may decrease during states of inflammation.³⁸ A mouse model study showed a 3.1-fold increase (P<.001) in ZIP14 expression in wild-type mice compared with an IL-6 -/- knock-down model after IL-6 exposure. The authors concluded that the upregulation of ZIP14 in the liver due to inflammatory cytokine upregulation decreases zinc availability in serum.³⁹ Additionally, serum zinc can overestimate the level of deficiency in IBD because approximately 75% of serum zinc is bound to albumin, which decreases in the setting of inflammation.^40-42

Alternatively, alkaline phosphatase (AP), a zinc-dependent metalloenzyme, may be a better evaluator of zinc status during periods of inflammation. A study in rats evaluated zinc through serum zinc levels and AP levels after a period of induced stress to mimic a short-term inflammatory state.⁴³ The researchers found that total body stores of zinc were unaffected throughout the experiment; only serum zinc declined throughout the experiment duration while AP did not. Because approximately 75% of serum zinc is bound to serum albumin,⁴² the researchers concluded the induced inflammatory state depleted serum albumin and redistributed zinc to the liver, causing the observed serum zinc changes, while total body zinc levels and AP were largely unaffected in comparison.⁴³ Comorbid conditions such as liver or bone disease can increase AP levels, which limits the utility of AP as a surrogate for zinc in patients with comorbidities.⁴⁴ However, even in the context of active IBD, serum zinc still is currently considered the best biomarker to evaluate zinc status.⁴⁵

Treatment—The recommended dose for zinc supplementation is 20 to 40 mg daily with higher doses (>50 mg/d) for patients with malabsorptive syndromes such as IBD.⁴⁶ It can be administered orally or parenterally. Although rare, zinc replacement therapy may be associated with diarrhea, nausea, vomiting, mild headaches, and fatigue.⁴⁶ Additional considerations should be taken when repleting other micronutrients with zinc, as calcium and folate can inhibit zinc reabsorption, while zinc itself can inhibit iron and copper reabsorption.⁴⁷

Vitamin D and Calcium

Low vitamin D levels (<50 nmol/L) and hypocalcemia (<8.8 mg/dL) are common in patients with IBD.^48,49

Pathophysiology—Vitamin D levels are maintained via 2 mechanisms. The first mechanism is through the skin, as keratinocytes produce 7-dehydrocholesterol after exposure to UV light, which is converted into previtamin D₃ and then thermally isomerizes into vitamin D₃. This vitamin D₃ is then transported to the liver on vitamin D–binding protein.⁵⁰ The second mechanism is through oral vitamin D₃ that is absorbed through vitamin D receptors in intestinal epithelium and transported to the liver, where it is hydroxylated into 25-hydroxyvitamin D (25[OH]D), then to the kidneys for hydroxylation to 1,25(OH)₂D for redistribution throughout the body.⁵⁰ This activated form of vitamin D regulates calcium absorption in the intestine, and optimal vitamin D levels are necessary to absorb calcium efficiently.⁵¹ Inflammation from IBD within the small intestine can downregulate vitamin D receptors, causing malabsorption and decreased serum vitamin D.⁵²

Vitamin D signaling also is vital to maintaining the tight junctions and adherens junctions of the intestinal epithelium. Weakening the permeability of the epithelium further exacerbates malabsorption and subsequent vitamin D deficiency.⁵² A meta-analysis of 27 studies including 8316 patients with IBD showed low vitamin D levels were associated with increased odds of disease activity (OR=1.53; 95% CI, 1.32-1.77), mucosal inflammation (OR=1.25; 95% CI, 1.06-1.47), and future clinical relapse (OR=1.23; 95% CI, 1.03-1.47) in patients with Crohn disease. The authors concluded that low levels of vitamin D could be used as a potential biomarker of inflammatory status in Crohn disease.⁵³

Vitamin D and calcium are further implicated in maintaining skeletal health,⁴⁷ while vitamin D specifically helps maintain intestinal homeostasis⁵⁴ and immune system modulation in the skin.⁵⁵

Cutaneous Manifestations—Vitamin D is thought to play crucial roles in skin differentiation and proliferation, cutaneous innate immunity, hair follicle cycling, photoprotection, and wound healing.⁵⁶ Vitamin D deficiency has been observed in a large range of cutaneous diseases including skin cancer, psoriasis, vitiligo, bullous pemphigoid, atopic dermatitis, and various types of alopecia.^56-59 It is unclear whether vitamin D deficiency facilitates these disease processes or is merely the consequence of a disrupted cutaneous surface with the inability to complete the first step in vitamin D processing. A 2014 meta-analysis of 290 prospective cohort studies and 172 randomized trials concluded that 25(OH)D deficiency was associated with ill health and did not find causal evidence for any specific disease, dermatologic or otherwise.⁶⁰ Calcium deficiency may cause epidermal changes including dry skin, coarse hair, and brittle nails.⁶¹

Diagnosis and Monitoring—The ECCO guidelines recommend obtaining serum 25(OH)D levels every 3 months in patients with IBD.⁶² Levels less than 75 nmol/L are considered deficient, and a value less than 30 nmol/L increases the risk for osteomalacia and nutritional rickets, constituting severe vitamin D deficiency.^63-65

An observational study of 325 patients with IBD showed a statistically significant negative correlation between serum vitamin D and fecal calprotectin (r=−0.19; P<.001), a stool-based marker for gut inflammation, supporting vitamin D as a potential biomarker in IBD.⁶⁶

Evaluation of calcium can be done through serum levels in patients with IBD.⁶⁷ Patients with IBD are at risk for hypoalbuminemia; therefore, consideration should be taken to ensure calcium levels are corrected, as approximately 50% of calcium is bound to albumin or other ions in the body,⁶⁸ which can be done by adjusting the calcium concentration by 0.02 mmol/L for every 1 g/L of albumin above or below 40 g/L. In the most critically ill patients, a direct ionized calcium blood level should be used instead because the previously mentioned correction calculations are inaccurate when albumin is critically low.⁶⁹

Treatment—The ECCO guidelines recommend calcium and vitamin D repletion of 500 to 1000 mg and 800 to 1000 U, respectively, in patients with IBD on systemic corticosteroids to prevent the negative effects of bone loss.⁶² Calcium repletion in patients with IBD who are not on systemic steroids are the same as for the general population.⁶⁵

Vitamin D repletion also may help decrease IBD activity. In a prospective study, 10,000 IU/d of vitamin D in 10 patients with IBD—adjusted over 12 weeks to a target of 100 to 125 nmol/L of serum 25(OH)D—showed a significant reduction in clinical Crohn activity (P=.019) over the study period.⁷⁰ In contrast, 2000 IU/d for 3 months in an RCT of 27 patients with Crohn disease found significantly lower CRP (P=.019) and significantly higher self-reported quality of life (P=.037) but nonsignificant decreases in Crohn activity (P=.082) in patients with 25(OH)D levels of 75 nmol/L or higher compared with those with 25(OH)D levels less than 75 nmol/L.⁷¹

These discrepancies illustrate the need for expanded clinical trials to elucidate the optimal vitamin D dosing for patients with IBD. Ultimately, assessing vitamin D and calcium status and considering repletion in patients with IBD, especially those with comorbid dermatologic diseases such as poor wound healing, psoriasis, or atopic dermatitis, is important.

Vitamin B₆ (Pyridoxine)

Pathophysiology—Pyridoxine is an important coenzyme for many functions including amino acid transamination, fatty acid metabolism, and conversion of tryptophan to niacin. It is absorbed in the jejunum and ileum and subsequently transported to the liver for rephosphorylation and release into its active form.³⁶ An observational study assessing the nutritional status of patients with IBD found that only 5.7% of 105 patients with food records had inadequate dietary intake of pyridoxine, but 29% of all patients with IBD had subnormal pyridoxine levels.⁷² Additionally, they found no significant difference in the prevalence of subnormal pyridoxine levels in patients with active IBD vs IBD in remission. The authors suggested that the subnormal pyridoxine levels in patients with IBD likely were multifactorial and resulted from malabsorption due to active disease, inflammation, and inadequate intake.⁷²

Cutaneous Manifestations—Cutaneous findings associated with pyridoxine deficiency include periorificial and perineal dermatitis,⁷³ angular stomatitis, and cheilitis with associated burning, redness, and tongue edema.³⁶ Additionally, pyridoxine is involved in the conversion of tryptophan to niacin, and its deficiency may manifest with pellagralike findings.⁷⁴

Because pyridoxine is critical to protein metabolism, its deficiency may disrupt key cellular structures that rely on protein concentrations to maintain structural integrity. One such structure in the skin that heavily relies on protein concentrations is the ground substance of the extracellular matrix—the amorphous gelatinous spaces that occupy the areas between the extracellular matrix, which consists of cross-linked glycosaminoglycans and proteins.⁷⁵ Without protein, ground substance increases in viscosity and can disrupt the epidermal barrier, leading to increased transepidermal water loss and ultimately inflammation.⁷⁶ Although this theory has yet to be validated fully, this is a potential mechanistic explanation for the inflammation in dermal papillae that leads to dermatitis observed in pyridoxine deficiency.

Diagnosis and Monitoring—Direct biomarkers of pyridoxine status are in serum, plasma, erythrocytes, and urine, with the most common measurement in plasma as pyridoxal 5′-phosphate (PLP).⁷⁷ Plasma PLP concentrations lower than 20 nmol/L are suggestive of deficiency.⁷⁸ Plasma PLP has shown inverse relationships with acute phase inflammatory markers CRP⁷⁹ and AP,⁷⁸ thereby raising concerns for its validity to assess pyridoxine status in patients with symptomatic IBD.⁸⁰

Alternative evaluations of pyridoxine include tryptophan and methionine loading tests,³⁶ which are measured via urinary excretion and require normal kidney function to be accurate. They should be considered in IBD if necessary, but routine testing, even in patients with symptomatic IBD, is not recommended in the ECCO guidelines. Additional considerations should be taken in patients with altered nutrient requirements such as those who have undergone bowel resection due to highly active disease or those who receive parenteral nutritional supplementation.⁸¹

Treatment—Recommendations for oral pyridoxine supplementation range from 25 to 600 mg daily,⁸² with symptoms typically improving on 100 mg daily.³⁶ Pyridoxine supplementation may have additional benefits for patients with IBD and potentially modulate disease severity. An IL-10 knockout mouse supplemented with pyridoxine had an approximately 60% reduction (P<.05) in inflammation compared to mice deficient in pyridoxine.⁸³ The authors suggest that PLP-dependent enzymes can inhibit further proinflammatory signaling and T-cell migration that can exacerbate IBD. Ultimately, more data is needed before determining the efficacy of pyridoxine supplementation for active IBD.

Vitamin B₁₂ and Vitamin B₉ (Folic Acid)

Pathophysiology—Vitamin B₁₂ is reabsorbed in the terminal ileum, the distal portion of the small intestine. The American Gastroenterological Association recommends that patients with a history of extensive ileal disease or prior ileal surgery, which is the case for many patients with Crohn disease, be monitored for vitamin B₁₂ deficiency.²³ Monitoring and rapid supplementation of vitamin B₁₂ can prevent pernicious anemia and irreversible neurologic damage that may result from deficiency.⁸⁴

Folic acid is primarily absorbed in the duodenum and jejunum of the small intestine. A meta-analysis performed in 2017 assessed studies observing folic acid and vitamin B₁₂ levels in 1086 patients with IBD compared with 1484 healthy controls and found an average difference in serum folate concentration of 0.46 nmol/L (P<.001).⁸⁴ Interestingly, this study did not find a significant difference in serum vitamin B₁₂ levels between patients with IBD and healthy controls, highlighting the mechanism of vitamin B₁₂ deficiency in IBD because only patients with terminal ileal involvement are at risk for malabsorption and subsequent deficiency.

Cutaneous Manifestations—Both vitamin B₁₂ and folic acid deficiency can manifest as cheilitis, glossitis, and/or generalized hyperpigmentation that is accentuated in the flexural areas, palms, soles, and oral cavity.^85,86 Systemic symptoms of patients with vitamin B₁₂ and folic acid deficiency include megaloblastic anemia, pallor, and fatigue. A potential mechanism for the hyperpigmentation observed from vitamin B₁₂ deficiency came from an electron microscope study that showed an increased concentration of melanosomes in a patient with deficiency.⁸⁷

Diagnosis and Monitoring—In patients with suspected vitamin B₁₂ and/or folic acid deficiency, initial evaluation should include a CBC with peripheral smear and serum vitamin B₁₂ and folate levels. In cases for which the diagnosis still is unclear after initial testing, methylmalonic acid and homocysteine levels can help differentiate between the 2 deficiencies. Methylmalonic acid classically is elevated (>260 nmol/L) in vitamin B₁₂ deficiency but not in folate deficiency.⁸⁸ Cut-off values for vitamin B₁₂ deficiency are less than 200 to 250 pg/mL forserum vitamin B₁₂ and/or an elevated level of methylmalonic acid (>0.271 µmol/L).⁸⁹ A serum folic acid value greater than 3 ng/mL and/or erythrocyte folate concentrations greater than 140 ng/mL are considered adequate, whereas an indicator of folic acid deficiency is a homocysteine level less than 10 µmol/L.⁹⁰ A CBC can screen for macrocytic megaloblastic anemias (mean corpuscular volume >100 fl), which are classic diagnostic signs of an underlying vitamin B₁₂ or folate deficiency.

Treatment—According to the Centers for Disease Control and Prevention, supplementation of vitamin B₁₂ can be done orally with 1000 µg daily in patients with deficiency. In patients with active IBD, oral reabsorption of vitamin B₁₂ can be less effective, making subcutaneous or intramuscular administration (1000 µg/wk for 8 weeks, then monthly for life) better options.⁸⁹

Patients with IBD managed with methotrexate should be screened carefully for folate deficiency. Methotrexate is a folate analog that sometimes is used for the treatment of IBD. Reversible competitive inhibition of dihydrofolate reductase can precipitate a systemic folic acid decrease.⁹¹ Typically, oral folic acid (1 to 5 mg/d) is sufficient to treat folate deficiency, with the ESPEN recommending 5 mg once weekly 24 to 72 hours after methotrexate treatment or 1 mg daily for 5 days per week in patients with IBD.¹ Alternative formulations—IV, subcutaneous, or intramuscular—are available for patients who cannot tolerate oral intake.⁹²

Final Thoughts

Dermatologists can be the first to observe the cutaneous manifestations of micronutrient deficiencies. Although the symptoms of each micronutrient deficiency discussed may overlap, attention to small clinical clues in patients with IBD can improve patient outcomes and quality of life. For example, koilonychia with glossitis and xerosis likely is due to iron deficiency, while zinc deficiency should be suspected in patients with scaly eczematous plaques in skin folds. A high level of suspicion for micronutrient deficiencies in patients with IBD should be followed by a complete patient history, review of systems, and thorough clinical examination. A thorough laboratory evaluation can pinpoint nutritional deficiencies in patients with IBD, keeping in mind that specific biomarkers such as ferritin and serum zinc also act as acute phase reactants and should be interpreted in this context. Co-management with gastroenterologists should be a priority in patients with IBD, as gaining control of inflammatory disease is crucial for the prevention of recurrent vitamin and micronutrient deficiencies in addition to long-term health in this population.