SAN FRANCISCO – Chronic contact dermatitis often is tied to hidden allergens found in shampoos, soaps, and body washes, according to Cory Dunnick, MD.“A lot of patients who get referred to my patch test clinic will have chronic dermatitis that isn’t responding to treatment or is worsening despite treatment, or they present with a pattern that is suggestive of contact dermatitis,” she said in an interview.
There is also a common perception that liquid body washes are better than bar soaps because they may be more moisturizing, but the results of a recently published study suggest otherwise, Dr. Dunnick of the department of dermatology at the University of Colorado at Denver, Aurora, said at the annual meeting of the Pacific Dermatologic Association.
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Dr. Dunnick was one of the investigators in a study that compared ingredients in the top-selling 50 bar soaps and 50 body washes on Amazon.com to determine if there was a difference with respect to allergen content. They obtained the ingredients list for all the products and compared them with the American Contact Dermatitis Society Core Allergen Series. Counter to the common belief, results of the study indicated that liquid soaps were likely the worse choice for sensitive patients: They contained far more preservative and surfactant allergens than bar soaps, and there was no difference in fragrance content between the two classes (Dermatitis. 2017 May 23. doi: 10.1097/DER.0000000000000289).
Of the 50 liquid soaps, 44 had one or more preservative allergens, compared with none of the bar soaps (P less than .001), and 34 had at least one surfactant allergen, compared with seven of the bar soaps (P less than .001). Forty-eight body washes had fragrance, as did 47 of the bar soaps.
The most common allergens in body washes were methylisothiazolinone (19 of 50), quaternium-15 (16), sodium benzoate (15), methylchloroisothiazolinone/methylisothiazolinone (12), DMDM hydantoin (10), and phenoxyethanol (9). None of these allergens appeared in any of the bar soaps.
“If you have a patient who you suspect has a contact allergy to a preservative or surfactant ingredient, then you can recommend perhaps switching to a bar soap, maybe one that is fragrance free,” advised Dr. Dunnick.
The most common allergen they found in body washes, methylisothiazolinone (MI), is becoming an increasing concern, she said. It has been around for many years but became more prevalent when the Food and Drug Administration decided in 2005 to allow higher concentrations of MI to be used in skin care products. “It’s a pretty strong sensitizer. As a result, we’re seeing a lot more allergy,” she noted.
Dr. Dunnick
This soap/body-wash allergen study sends a clear message to dermatologists to individualize recommendations, she said. “A lot of dermatologists recommend what they think are mild soaps, but they don’t necessarily think about what contact allergens might be in those soaps, so maybe they need to make more specific recommendations. They might recommend Dove soap,” but there are different Dove soaps, she pointed out.
A bigger challenge is finding a shampoo for sensitive patients. Almost all contain fragrances, and MI is an ingredient in many shampoos as well. Dr. Dunnick has found the DHS brand, which is fragrance free, to be helpful in some cases, and the Nonscents brand, also fragrance free, is sometimes recommended as safe.
But, in the end, recommendations must be individualized for the patient’s specific allergies, and that requires a thorough work-up. “You don’t know what they are unless you do the patch test,” she said.
Dr. Dunnick reported having no relevant financial disclosures.