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Allergen Trends and the 2020 Allergen of the Year

At the 2020 Winter Clinical Dermatology Conference, David E. Cohen, MD, MPH, recapped attendees on the trends seen in allergens and contact dermatitis seen in 2019. He later introduced the Allergen of the Year as selected by the American Contact Dermatitis Society.

In 2019, dermatologists saw some changes in thought regarding contact dermatitis. For example, started Dr Cohen, “We used to think thiurams were the most common cause of contact dermatitis from gloves, but that shifted dramatically to carbamates.” He continued to reflect how important the quick, 1-hour allergy alert test became for determining reactions and hypersensitivity to hair dye. “That can pick up over 90% of your patients who might be allergic to hair dye,” Dr Cohen noted.

In his presentation, Dr Cohen shared a table listing some of the top causes of dermatitis as published in Dermatitis. Preservatives commanded the top 20 allergens, followed by fragrances, metals, rubber, solvents. 

 “For the second time, in all the time we’ve chosen an Allergen of the Year, parabens were named the 2019 Non-allergen of the Year because of their really infrequent demonstration of allergic contact dermatitis.” Similarly, lanoline and preservatives may actually be less problematic for dermatitis conditions than fragrances.

Preservatives have demonstrated long-range decreases in formaldehyde-releasing preservatives, including quaternium 15, bronopol, and imidizolidiyl urea, and have been replaced by other systems. “We all have this paraben-oia,” stated Dr Cohen. “Only 0.6% of people patch-tested were reactive to lanolin, and more frequently used preservatives are ten and twenty-times more frequent sensitizers, yet we don’t worry about them when they’re in products.” He continued to explain that parabens are in an overwhelming majority of hygienic products on the market, such as:

  • 66% to 87% of women’s cosmetics;
  • 30% of shampoo;
  • 77% to 82% of lipsticks and lip liners;
  •  30% of sunblocks; and
  • 23% of wipes.

Instead, the most common cause of allergic contact dermatitis from cosmetic agents. It can be difficult to treat due to constant changes. An estimated 3.5% to 4.5% of the general population and 20% of the patch test population may be allergic to one or more fragrances. However, the wash-on, wash-off formulas, such as shampoos and face washes, can be less problematic than leave-on products such as solid antiperspirant and eye shadow.

Systemic contact dermatitis should also be noted by the dermatologist. These are allergic reactions to a noncutaneous uses. Common causes include metals, fragrances, propylene glycol, teas, and extracts. The contact dermatitis caused by noncutaneous sources may occur when the allergen bypasses the dendritic cell process and binds to T-cell receptors. Patients who demonstrate systemic contact dermatitis may say something such as “I eat it and within minutes, I have this rash!” Dermatologists should be aware.

Dr Cohen closed with revealing the 2020 Allergen of the Year, isobornyl acrylate. It’s everywhere: in coatings, adhesives, paints, and inks, and also used as a plasticizer in various materials. In addition, isobornyl acrylate is located in diabetic devices. The patch test should be used in 0.1% petrolatum.


Cohen DE. Contact dermatitis pearls. Presented at: 2020 Winter Clinical Dermatology; Kohala Coast, HI; January 19, 2020.

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