Because she has an eczema condition, Michelle Kirn intently reads ingredient labels on baby wipes, soaps and other household items to avoid allergic reactions that she says were caused by a commonly used preservative.

Ms. Kirn, 37, says she believes that nerve damage and scarring to her hands stemmed from using wipes that contained the preservative methylisothiazolinone, or MI.

Still, when her throat began to swell, she says she did not think to check the label of her new mouthwash, Colgate Total Lasting White.

“I thought I was developing allergies to foods,” Ms. Kirn, a consultant in Breinigsville, Pa., said. “I felt like I constantly had a sore throat.”

Colgate-Palmolive introduced that product in August, and it may be the only popular mouthwash to contain MI, an ingredient added to deter the growth of bacteria. But it can cause rashes and skin irritations in people who are allergic to it. The company chose that preservative, according to Stephanie Clark, a spokeswoman for Colgate, because it worked best for that particular formula.

Experts say it’s an unusual additive for a mouthwash, an expansion of the chemical into products occurring at the same time that major consumer products companies — including Kimberly-Clark, Johnson & Johnson and Unilever — have begun removing it from lotions and wipes.

“It’s not a preservative that we’ve seen commonly in products that are used anywhere but on the skin,” Dr. Bruce A. Brod, president-elect of the American Contact Dermatitis Society, said. “When people are exposed on a daily basis to MI, we think the rates of sensitization are going up.”

Compounding the problem, Dr. Brod said, is a lack of awareness among both patients and doctors. Ms. Kirn said her hands “looked like I had been in a fire” several months after she began using Huggies Simply Clean wipes, but she didn’t discover her allergy to the product until months later.

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https://www.nytimes.com/2015/01/24/business/allergy-trigger-found-in-many-personal-care-items-comes-under-greater-scrutiny.html