Every year the American Contact Dermatitis Society announces an “allergen of the year,” in order to make experts and consumers aware of an under-the-radar ingredient causing an increasing number of reactions. This year, it’s our not-so-well-known friend methlisothiazolinone. “Methlisothiazolinone has recently been introduced to cosmetics and toiletries, and the use of it increased dramatically in the past few years,” says Kathryn Zug, MD, professor of dermatology at the Geisel School of Medicine at Dartmouth, and member of the North American Contact Dermatitis Group. “Even companies I’ve recommended based on less frequent use of allergens have started using the ingredient, which I find concerning.” While you may see it listed as “methylchloroisothiazolinone/methylisothiazolinone,” this is a combination preservative with a low concentration of the allergen. Now methylisothiazolinone is being used on its own in products, and the concentration of it can be 25 times higher than when it is used in the combination preservative. This, and more cases of allergy to this preservative being reported, has allergy experts on notice. More from Prevention: Are You Allergic To Sunscreen? How To Choose And Apply Foundation
