Patch testing is the most important diagnostic tool for the assessment of allergic contact dermatitis.
This study documents the North American Contact Dermatitis Group (NACDG) patch testing results from January 1, 2013, to December 31, 2014.
At 13 centers in North America, patients were tested in a standardized manner with a screening series of 70 allergens. Data were manually verified and entered into a central database. Descriptive frequencies were calculated, and trends were analyzed using χ2 test.
A total of 4871 patients were tested. There were 3255 patients (66.8%) who had at least 1 positive reaction and 2412 patients (49.5%) who were ultimately determined to have a primary diagnosis of allergic contact dermatitis. A total of 434 patients (8.9%) had occupationally related skin disease. There were 9726 positive allergic reactions. Compared with the previous reporting periods (2011–2012 and 2001–2012, including at least three 2-year cycles), positive reaction rates for the top 25 screening allergens statistically increased for 2 allergens: methylchloroisothiazolinone/methylisothiazolinone (6.4%; risk ratios, 1.26 [1.07–1.50] and 2.08 [1.84–2.37]) and hydroxyethyl methacrylate (2.6%; risk ratios, 1.34 [1.02–1.76] and 1.23 [1.00–1.51]). Methylisothiazolinone, which was added to the screening series for this 2013–2014 cycle, had the third highest positive reaction rate of allergens tested (10.9%). Four other newly added allergen preparations—formaldehyde 2% (7%), diphenylguanidine (3.8%), propylene glycol 100% (2.8%), and benzophenone-4 (2.1%)—all had reaction rates greater than 2%. Twenty-one percent of tested patients had at least 1 relevant allergic reaction to an allergen not on the NACDG series; 14.6% of these were occupationally related. The T.R.U.E. TEST (SmartPractice Denmark, Hillerød, Denmark) would have hypothetically missed one quarter to one third of reactions detected by the NACDG screening series.
These results confirm that the epidemic of sensitivity to methylisothiazolinone previously documented in Europe is also occurring in North America. Patch testing with allergens beyond a standard screening tray is necessary for the complete evaluation of occupational and nonoccupational allergic contact dermatitis.
From the *Division of Dermatology, Department of Medicine, University of Toronto, Canada; †Department of Dermatology, University of Minnesota; ‡Minneapolis VAMC, Minnesota; §Columbia University Medical Center, New York, NY; ∥Department of Medicine, Division of Dermatology, McGill University Health Centre, Montreal, Canada; ¶University of California, San Francisco; #Department of Dermatology, Cleveland Clinic Lerner College of Medicine, Ohio; **Department of Dermatology, Pennsylvania State University, Hershey; ††DS Research, Louisville, KY; ‡‡Division of Dermatology, Group Health Associates, Cincinnati, Ohio; §§Department of Dermatology, Keck School of Medicine, University of Southern California, Los Angeles; ∥∥Department of Medicine, Division of Dermatology, University of Ottawa, Canada; ¶¶The Ohio State University, Columbus; ##Section of Dermatology, Dartmouth Medical Center, Lebanon, NH.
Address reprint requests to Joel G. DeKoven, MD, MHSc, M1-736, 2075 Bayview Avenue, Sunnybrook Health Sciences Centre, Toronto, Ontario Canada M4N 3M5. E-mail: firstname.lastname@example.org.
The authors have no funding or conflicts of interest to declare.
Disclaimer: 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.