Sensitization to the isothiazolinones MCI (methylchloroisothiazolinone) and MI (methylisothiazolinone), which are used as preservatives in a wide variety of personal and household products, is both frequent and underdiagnosed in U.S. children, according to a report published in Pediatric Dermatology.

These agents are compatible with surfactants and emulsifiers, and because they maintain biocidal activity across a broad range of pH levels they are frequently used as preservatives in products such as wet wipes; shampoos and hair conditioners; soaps, cleansers, and disinfectants; and laundry products. However, they are known to cause contact dermatitis very frequently, and are among the top five contact allergens identified in infants’ patch tests.

A recent survey showed that among 152 pediatric skin care products available at major retail stores, 20% contained MI. These were specifically targeted to infants and children, advertised as being “hypoallergenic,” “natural,” good for “sensitive” skin, and containing “gentle ingredients,” said Alina Goldenberg, MD, of the department of dermatology at the University of California, San Diego, and her associates.

During the past 10 years, only 35 U.S. cases of a positive patch-test reaction to MCI and/or MI have been reported in the literature. To get a more accurate estimate of the true prevalence of pediatric sensitization to MCI and MI, the investigators analyzed information in a database of patch-test results, the Provider Contact Dermatitis Registry. They focused on 1,056 patch tests performed during a 1-year period.

They found 37 positive reactions to combined MCI/MI and another 39 reactions that were negative to combined MCI/MI but positive to MI alone. This shows how important it is to test for sensitization to both formulations separately, Dr. Goldenberg and her associates noted ( Pediatr Dermatol. 2017 Mar;34[2]:138-43 ).

In stark contrast to the reported 35 cases across the entire country during a 10-year period, the investigators found 76 cases (1%) in 1,056 patch tests during a 1-year period.

When test results for MCI/MI and MI alone were compared with those for all other allergens, children sensitized to the isothiazolinones showed marked differences: They were significantly younger, and the location of their dermatitis was more likely to involve the groin and buttocks. This probably is due to the increased use of wet wipes containing MCI and MI being used to clean up urinary and fecal accidents in young children, the researchers said.

The Society for Pediatric Dermatology supported the work. Dr. Goldenberg reported having no relevant financial disclosures; an associate reported serving as a consultant for Johnson & Johnson.


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