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Epidemic of Isothiazolinone Allergy in North America: Prevalence Data From the North American Contact Dermatitis Group, 2013–2014

Zirwas, Matthew J. MD*; Hamann, Dathan MD*; Warshaw, Erin M. MD; Maibach, Howard I. MD; Taylor, James S. MD§; Sasseville, Denis MD; DeKoven, Joel G. MD, MHSc; Fransway, Anthony F. MD#; Mathias, C.G. Toby MD**; Zug, Kathryn A. MD††; DeLeo, Vincent A. MD‡‡; Fowler, Joseph F. MD§§; Marks, James G. MD∥∥; Pratt, Melanie D. MD¶¶; Belsito, Donald V. MD##

doi: 10.1097/DER.0000000000000288

Background Preservative sensitivity patterns evolve with changing use patterns in products. During the last decade, the use of methylisothiazolinone (MI) at higher concentrations in both leave-on and rinse-off products has significantly increased. This is the first North American Contact Dermatitis Group reporting cycle that includes both methylchloroisothiazolinone (MCI)/MI and MI data.

Objective The aim of this study was to report the prevalence of isothiazolinone allergy (MCI/MI and MI) in the North American Contact Dermatitis Group patch-test population from January 1, 2013, to December 31, 2014.

Methods At 13 centers in North America, 4860 patients were patch tested in a standardized manner with a series of 70 allergens, including MCI/MI 0.01% aqueous (aq) and MI 0.2% aq.

Results Three hundred five patients (6.3%) had a positive reaction to MCI/MI; this is a significant increase from the previous cycle (5.0%, 2011–2012; P = 0.011). Five hundred twenty-one patients (10.7%) had a positive reaction to MI. These 2 isothiazolinones were among the most common preservative allergens in the 2013 to 2014 cycle; 11.9% of patch-tested individuals were allergic to 1 or both isothiazolinones. Individuals with MCI/MI and MI allergy were significantly more likely to have occupationally related skin disease (P < 0.0001) and hand dermatitis (P < 0.0001, P = 0.0474).

Conclusions The epidemic of isothiazolinone sensitivity documented in Europe is now in North America. Patch testing with only MCI/MI 0.01% aq will miss approximately half of isothiazolinone allergy cases, whereas testing with only MI 0.2% aq will miss approximately 10% of isothiazolinone allergy cases.

From the *Division of Dermatology, The Ohio State University, Columbus; †The University of Minnesota and the Minneapolis VAMC; ‡University of California, San Francisco; §Cleveland Clinic, OH; ∥McGill University Health Centre, Montreal, Canada; ¶University of Toronto, Canada; #Associates in Dermatology, Fort Myers, FL; **Group Health Associates, Cincinnati, OH; ††Dartmouth Medical Center, Lebanon, NH; ‡‡St. Luke’s Roosevelt Hospital Center, New York; §§Dermatology Specialists, Louisville, KY; ∥∥Pennsylvania State University, Hershey, PA; ¶¶University of Ottawa, Ontario, Canada; ##Columbia University Medical Center, New York, NY.

Address reprint requests to Dathan Hamann, MD, 764 S 3rd St, Columbus, OH 43206. E-mail:

This material is the result of work supported with resources and the use of facilities at the Minneapolis Veterans Affairs Health Care System.

The authors have no conflicts of interest to declare.

The views expressed in this article are those of the authors and do not necessarily represent the position or policy of the Department of Veterans Affairs or the US Government.

© 2017 American Contact Dermatitis Society
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