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Updates in Contact Dermatitis

Up to 40% of reactions are missed using the True-Test compared with NA-70, said David E. Cohen, MD, during his presentation at the 2019 Fall Clinical Dermatology Conference in Las Vegas, NV. Dr Cohen is the Charles and Dorothea Harris Professor of dermatology, vice chairman for clinical affairs, and director of allergic, occupational and environmental dermatology at New York University School of Medicine in New York, NY.

Dr Cohen reviewed the latest trends in contact dermatitis, such as allergens in cosmetic products. According to him, women use 12 personal care products a day with 168 unique ingredients, and men use 6 products with 85 ingredients.

Among 256 consumer product ingredient lists that were analyzed online compared with the ingredient lists on CAMP, SkinSAFE, and consumer product information databases, 28% contained an omissions or addition, said Dr Cohen. In addition, 31 had core ACDS allergens. In baby wipes, 51 tested with chromotropic acid method (CAM) and 24% of those with CAM had formaldehyde despite not declaring formaldehyde as an ingredient, he added.

Dr Cohen reviewed trends in preservative allergies, noting that there was a statistically significant decrease in rates for 3 formaldehyde-releasing preservatives. However, 7 of the top 20 allergens are still preservatives. In the past 10 years, Dr Cohen said, paraben mix showed statistically significant decrease in patch test positivity rate and has the lowest prevalence of positivity (0.6%) of any major preservative. The overall dominance of preservatives is accounted for by the “unprecedented epidemic of methylisothiazolinone (MI) contact allergy,” said Dr Cohen, as well as increases in other non-formaldehyde releasers.

Formaldehyde 2% is ranked fourth in the top 10 allergens and was “Allergen of the Year” in 2015. It is present in textiles, wood, preservatives, and plastics. According to Dr Cohen, formaldehyde is present in “Brazilian-style keratin” hair straighteners. Despite the brands claiming no formaldehyde content, 15 out of 16 brands exceed the safety limits of 0.2%, he added. Alternative names for formaldehyde include methylene glycol, an aldehyde, bonded aldehyde, or morbicid acid. In addition, contact dermatitis from formaldehyde has been reported with aspartame. 

Methylisothiazolinone, the “2013 Allergen of the Year,” requires patching testing at higher concentrations to detect allergy, said Dr Cohen. It was banned as a leave-in product in Europe in 2014.

A notable non-formaldehyde releasing preservative is iodopropynyl butylcarbamate, which ranks 16 in the most common allergens. According to Dr Cohen, it is an emerging allergen with an increasing prevalence and used in industrial preparations, such as paints and metal working fluids, as well as in personal care products in combination with formaldehyde releasing agents.

The most common cause of allergic contact dermatitis is from fragrances in cosmetic agents, said Dr Cohen, with sensitization risk highest in lipstick, solid antiperspirants, eye shadow, and face cream. The lowest risk is with shampoo, conditioner, and facial cleanser, he added.

A few screening allergens are insufficient to detect the class, noted Dr Cohen, adding that 32% of patients had positive reactions to FM II but had negative reactions to FM 1. Essential oils can confound the work up, and oxidized agents, such as linalool, limonene and geraniol, are better screening agents.

Dr Cohen reviewed a study that assessed contact dermatitis to essential oils among 13,398 participants. The most common essential oils that caused a reaction included ylang-ylang, jasmine, sandalwood, peppermint, tea tree, and lavender.

Rubber allergens are most commonly associated with occupations, including medical and surgical gloves, he added.

Alkyl Glucoside is a nonionic surfactant used in shampoos, liquid cleansers, shower gels, and leave-on products, including sunscreen, and was the 2017 Allergen of the Year. Propylene Glycol and Parabens were the Allergens of the Year for 2018 and 2019, respectively.

Acrylics are monomers that are used in adhesives, such as in nails, hair sprays, and some fragrances, said Dr Cohen, as well as in diabetes devices. Of patients who are allergic to cyanoacrylates, one-third will be more likely have allergic reactions to other acrylics, he added.

Isoborynyl arcylate was named the 2020 Allergen of the Year, said Dr Cohen, it is not an adhesive but in the body of it and is used in paints and glues, among other products.

He concluded his presentation by saying preservatives continue to be a problem, fragrances can be hard to identify and stay on top of for patients who have allergies to one or more ingredients, and patients with atopic dermatitis may also have allergic contact dermatitis.


Cohen DE. New concepts in contact dermatitis. Presented at: 2019 Fall Clinical Dermatology Conference; October 19, 2019; Las Vegas, NV.

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