As ingredients in household and personal care products continue to change, so, too, does the landscape of causes of contact dermatitis and recommendations for patch testing, according to Matthew J. Zirwas, M.D., director, Ohio Contact Dermatitis Center, Columbus, Ohio. In his update during MauiDerm 2016, he said the most important thing dermatologists should be aware of is the rising importance of methylisothiazolinone (MI) as a contact allergen.
Among other current issues, glucosides are replacing betaines as a contact dermatitis allergen found in personal care products, and in laundry products. Detergents are now a bigger cause of contact dermatitis than fragrances and dyes. Noteworthy as well: About half of fragrance allergies are being missed when testing is done using only the T.R.U.E. Test.
Prevalance in products increasing
Dr. Zirwas said that data being released later in 2016 will rank MI as a leading contact allergen. It is commonly found in paint, where it acts as an airborne allergen, and in an increasing number of personal care products (ie., shampoos, hair conditioners, liquid soaps). Patients can develop a localized or widespread rash or itching.
In addition to recognizing the importance of MI as a cause of contact dermatitis, dermatologists should also know that it will not be detected using the T.R.U.E. Test, which includes methylchloroisothiazolinone (MCI) but not MI. In addition, MI allergy is often missed using the MCI-MI mix that is in common use in expanded Finn Chamber testing.
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“MI is now found in so many different products that every patient being patch tested should be evaluated for MI allergy using the 2000 ppm MI in petrolatum,” Dr. Zirwas said.
Glucosides are also becoming more common as an ingredient in personal care products, especially shampoos and liquid facial cleansers, where they are used as a low irritancy lathering agent. In addition, glucosides, like MI, are not detected with the T.R.U.E Test. Glucoside allergy may be suspected in patients who present with dermatitis involving the face or eyelids, Dr. Zirwas said.
The importance of detergents as a cause of irritant contact dermatitis associated with laundry products has become more apparent as more and more of those products are being formulated without fragrances and dyes. The residue left by detergents in laundered clothing and other articles causes an irritant dermatitis rather than an allergic reaction. The colder the water and the harder the water, the greater the residue and the more likely a problem can occur.
“When making a recommendation to patients with a dermatitis thought to be related to laundry detergent, it is more important to counsel them about selecting a product that has a low irritancy and low residue detergent than to recommend one without fragrances or dyes,” Dr. Zirwas said. “The brand All Free Clear is the only product on the market that I am aware of that contains a low irritancy surfactant blend,” he said.
Fragrance allergy testing
Discussing testing for fragrance allergies, Dr. Zirwas noted that the diagnosis is being missed in many patients who are tested only with the T.R.U.E. Test for two reasons — the panel does not contain Fragrance Mix 2, which contains contact allergens of rising importance; and the T.R.U.E. Test is associated with a relatively high false negative rate among people with allergies to Fragrance Mix 1 and balsam of Peru.
“Ideally, initial testing for fragrance allergy should include the T.R.U.E. Test supplemented with Finn Chamber testing for allergy to fragrance mix 1, balsam of Peru, and fragrance mix 2. If the T.R.U.E. Test only is used and it is negative, or if a patient tests positive for certain allergens using the T.R.U.E. Test but is not getting better by avoiding those agents, then further testing should be conducted using Finn Chambers,” he said.
Dr. Zirwas is a consultant for Sun Laundry Products, the manufacturer of All Free Clear.