Methylisothiazolinone in baby wipes: a rising star among causes of contact dermatitis

To the Editor: Methylisothia-zolinone (MI) is a preservative that has been used alone in cosmetic and personal products since the early 2000s.1 Before that time, MI was combined with methylchloroiso-thiazolinone in the widely used preservative Kathon CG (Dow Chemical Company), in a 1:3 ratio with the concentration of MI limited to 3.75 parts per million. This limit was subsequently increased to 100 parts per million, and MI is now being widely used in consumer products.

MI has been included in our baseline patch test series since 2011, following European reports of an increasing prevalence of MI allergy.1 We have subsequently seen a rapid increase in the number of patients with contact allergy to MI. Our rate of positive reactions on MI patch tests to November 2013 was 11.3% (40 patients who had relevant reactions of a total 353), compared with a rate of 3.5% (15/428) in 2011 and 8.4% (38/454) in 2012. MI is now the most common cause of allergic contact dermatitis in our patient population.

Our Australian experience is reflected overseas. An increase in the frequency of allergic reactions to MI has been reported in Europe2,3 and, in the United States, MI was named the 2013 “Contact Allergen of the Year” by the American Contact Dermatitis Society, which bestows this “award” to highlight important and emerging allergens.

Among our patient population, the most common source of MI is disposable wet wipes,4 now commonly used in nappy changing. MI is present in many popular brands of wipes used in Australia. Interestingly, it is parents who use baby wipes on their children who are presenting with hand dermatitis, although it is likely that allergic contact dermatitis involving the groin in children may not be diagnosed accurately.

Other common consumer sources of MI include make-up removal wipes, shampoos, conditioners, body washes, moisturisers, sunscreens and deodorants. Occupational sources include paints, cooling tower water and cutting oils.

The use of disposable wipes in nappy changing, personal care, cosmetic removal and cleaning has increased rapidly. Preservatives are required to prevent bacterial contamination in moist wipes. Medical practitioners and consumers should be aware of the potential for allergic contact dermatitis to develop to MI from wipes, in particular causing persistent hand dermatitis.