Treat contact dermatitis by avoiding irritating ingredients

May 1, 2010

Montreal - The key to warding off skin reactions to specific cosmetic products is to stop using the offending products, as treatment will fail if exposure continues, and desensitization cannot be done, says an associate professor at McGill University in Montreal.

Montreal - The key to warding off skin reactions to specific cosmetic products is to stop using the offending products, as treatment will fail if exposure continues, and desensitization cannot be done, says an associate professor at McGill University in Montreal.

“It’s surprising how little we know about the products we use,” says Denis Sasseville, M.D., a past president of the Canadian Contact Dermatitis Society and director of the Contact Dermatitis Clinic at the Royal Victoria Hospital, Montreal. “Patch testing is the key (to identifying allergic reactions).”

Dr. Sasseville says that while the incidence of adverse reactions to cosmetics including soaps, perfumes, deodorants, make-up, nail polish, hair products, fragrances and sunscreens remains low, it still represents more than 50 percent of skin reactions that present at his clinic.

“Many patients say that they are allergic, but they are not,” Dr. Sasseville explains. “After a comprehensive investigation, we find out that they have irritancy and not true allergy.”

Fragrance culprits

Fragrances, which contain as many as 300 chemicals in one bottle, represent the most common cause of allergic contact dermatitis to cosmetics. In a recent analysis conducted by the North American Contact Dermatitis Group, 9.1 percent of patients were allergic to the Fragrance Mix and 10.6 percent were allergic to balsam of Peru, another marker of allergy to fragrance materials. These natural or synthetic chemicals can be found in perfumes, colognes, deodorants, moisturizers, essential oils, sunscreens and many shampoos.

Dr. Sasseville notes that even products that are listed as unscented or fragrance-free contain a masking fragrance.

“There are no regulations on things that are listed as unscented,” Dr. Sasseville says.

Reactions to fragrances occur at sites such as wrists or the neck, where individuals would have dabbed themselves with a fragrance.

Ideally, preservatives that are incorporated in cosmetic products should be at low concentrations, odorless, tasteless, colorless, stable, nonsensitizing, nonirritating, and nontoxic. “The ideal preservative had not yet been found,” Dr. Sasseville tells Dermatology Times.

Parabens

One of the most commonly used family of preservatives in food and cosmetics is the parabens, which has a low rate of sensitization. When cases of allergic reactions to parabens started to be reported, industry explored alternatives and came up with formaldehyde releasers.

Formaldehyde itself is rarely used because it is an irritant, a sensitizer and a potential carcinogen. However, the formaldehyde releasers, as a group, proved to be more sensitizing than the biocides that they were meant to replace.

The industry is still using parabens more than any other preservative, which is good from an allergic point of view, according to Dr. Sasseville. Unfortunately, parabens are now subject to bad press because of purported estrogenic effects and tumor-enhancing potential in breast cancer.

Hair dyes often contain a substance called paraphenylendiamine (PPD), which can trigger allergic contact dermatitis. Many individuals become sensitized to PPD from black henna temporary tattoos, and then have a delayed type-IV hypersensitivity reaction to PPD. Black henna tattoos are often marketed as a harmless and temporary alternative to a permanent tattoo despite the concentrations of PPD being much higher in these tattoos than in hair dyes.

These individuals can also react to other “para-amino” chemicals, including dyes, such as paratoluenediamine, 4-aminophenol and 2-nitro-4-phenylenediamine, the local anesthetic benzocaine, PABA, antioxidants in black rubber, and some textile dyes that can cross-react with PPD.

“Young people, sensitized to PPD from temporary tattoos, who later train as hairdressers can have very severe reaction to hair dyes,” explains Dr. Sasseville, noting that hair stylists start out as apprentices who mainly wash hair and that these reactions occur once they begin working with dyes. “Such people will need to look for other careers.”

Nail polish

Nail polish contains resins, plasticizers, hardeners, and solvents that can result in allergic contact dermatitis at sites where nails may touch such as the eyelids and neck, Dr. Sasseville notes.

The most common allergen in nail polish is tosylamide formaldehyde resin. The ingredients in artificial nails contain acrylates that are strongly allergenic, he adds. They can cause severe periungual dermatitis and sometimes can cause permanent loss of nails, as well as painful paresthesias that may be long-term and are due to a neurotoxic effect independent of allergy.

Sunscreen

Sunscreens serve to block out the sun, but the ingredients in sunscreens can result in allergic and photo allergic contact dermatitis.

“The reactions can occur on sun-exposed areas only when the reaction is photoallergic, and also on non sun-exposed skin with a pure contact allergic reaction,” Dr. Sasseville says.

One of the most common ingredients used in sunscreen products are benzophenones that can lead to the aforementioned delayed-hypersensitivity reactions, as well as photocontact urticaria, contact urticaria and anaphylaxis. Contact reactions to benzophenones in sunscreens were first observed in the 1970s.

Dermatologists should patch test for benzophenone-3 and benzophenone-4, advises Dr. Sasseville. Benzophenones can also be found in shampoos and hairsprays.

Shellac contained in waterproof mascaras is an emerging allergen that has been identified, Dr. Sasseville notes.

Disclosures: Dr. Sasseville is a consultant for Spexell Pharma and Basilea Pharmaceuticals.

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