Diet and allergic contact dermatitis

Systemic contact dermatitis (SCD) is a condition that occurs in patients sensitized by contact, whether orally, by inhalation, transcutaneously or intravenously. This can lead to a type 4 hypersensitivity reaction, said Peggy A. Wu, MD, MPH, dermatologist at University of California Davis Dermatology, Sacramento, Calif.

She discussed the main causes of these reactions and how they relate to a person’s diet in her presentation at the 2022 American Academy of Dermatology (AAD) Annual Meeting, held March 25-29. in Boston, Massachusetts.

She pointed out that the main substances that cause SCD include drugs, plants, metals, balsam or Peru/fragrances, benzoic acid/benzoates, gallates, propylene glycol, aspartame/ formaldehyde and sorbic acid.

Of the top 10 allergens reported from 2017 to 2018, according to Wu, 4 are related to preservatives: methylisothiazolinone, methylchloroisothiazolinonem, formaldehyde and benzisothiazolinone. Additionally, 3 were fragrances (Fragrance Blend I, Linalool Hydroperoxides and M. pereirae resin/ balsam of Peru), 2 metals (nickel sulphate hexahydrate and cobalt) and 1 hair dye (4-phenylenediamine).

Nickel SCD, Wu explained, can clinically present on the palms and soles of the feet as a vesicular rash and pompylox and can also manifest on the bilateral extensor elbows. Irritants can be found in many places like metals can be found in foods. For example, chromium can be found in potatoes, meats, tea, nuts, grapes, nutritional supplements, multivitamins, and dyes. Even cobalt can be found in flaxseeds, chickpeas, chocolate, nuts, and vitamin B12.

Balsam of Peru, which is derived from the resin of the topical myroxylon balsamum pereirae tree in Central and South America, is a marker of fragrance allergy, she said. A clinical presentation of Peru balsam allergy includes perioral, genital, perianal, symmetrical intertriginous, and vesicular atopic dermatitis (AD). Benzoic acid or benzoates, a component of Balsam of Peru, is an antimicrobial preservative found in personal care products, foods and beverages.

SCD reactions, according to Wu, are more common in people 60 and older. Moreover, AD patients are more allergic to benzoic acid than the general population. Benzoic acid is the forty-second most common allergen in AD patients compared to seventy-ninth for the general population, she said. Gallates allergen is an antioxidant that has a perioral or chelite clinical presentation.

Wu pointed out how to talk with SCD patients. She explained that a doctor should instruct the patient to avoid topical contact with allergens. Then, if after 2 months there is no significant improvement, try an elimination diet to see if any foods are causing a reaction. Continue to avoid the diet for at least 1 month to assess skin response.

She concluded her presentation with additional suggestions. “If a rash does not improve with topical avoidance, there may be a significant component of systemic contact dermatitis. Start with a one-month trial,” she wrote in the presentation. There are a number of tools, documents and websites to guide you and your patients Be aware of other common allergens (latex, poison ivy/oak/sumac) and associated foods.


Shi V, Armstrong AW, Friedman AJ, et al. Dietary triggers and changes in common skin conditions – an evidence-based approach. Presented at the 2022 Annual Meeting of the American Academy Dermatology Association; March 25-29, 2022; Boston, Massachusetts.


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