North American contact dermatitis group patch test results: 2011-2012.

BACKGROUND

Patch testing is an important diagnostic tool for assessment of allergic contact dermatitis (ACD).

OBJECTIVE

This study documents the North American Contact Dermatitis Group (NACDG) patch-testing results from January 1, 2011, to December 31, 2012.

METHODS

At 12 centers in North America, patients were tested in a standardized manner with a series of 70 allergens. Data were manually verified and entered into a central database. Descriptive frequencies were calculated, and trends analyzed using χ statistics.

RESULTS

Four thousand two hundred thirty-eight patients were tested; of these, 2705 patients (63.8%) had at least 1 positive reaction, and 2029 (48.0%) were ultimately determined to have a primary diagnosis of ACD. Four hundred eight patients (9.6%) had occupationally related skin disease. There were 7532 positive allergic reactions. As compared with previous reporting periods (2009-2010 and 2000-2010), positive reaction rates statistically increased for 6 allergens: methylchloroisothiazolinone/methylisothiazolinone (5.0%; risk ratios [RRs]: 2.01 [1.60-2.52], 1.87 [1.61-2.18]), lanolin alcohol (4.6%; RRs 1.83 [1.45-2.30], 2.10 [1.79-2.47]), cinnamic aldehyde (3.9%; 1.69 [1.32-2.15], 1.53 [1.28-1.82]), glutaral (1.5%; 1.67 [1.13-2.48], 1.31 [1.00-1.71]), paraben mix (1.4%; 1.77 [1.16-2.69], 1.44 [1.09-1.92]), and fragrance mix I (12.1%; RRs 1.42 [1.25-1.61], 1.24 [1.14-1.36]). Compared with the previous decade, positivity rates for all formaldehyde-releasing preservatives significantly decreased (formaldehyde 6.6%; RR, 0.82 [0.73, 0.93]; quaternium-15 6.4% RR 0.75 [0.66, 0.85]; diazolidinyl urea 2.1%; RR, 0.67 [0.54, 0.84]; imidazolidinyl urea 1.6%, 0.60 [0.47, 0.77]; bronopol 1.6%; RR, 0.60 [0.46, 0.77]; DMDM hydantoin 1.6%; RR, 0.59 [0.54, 0.84]). Approximately a quarter of patients had at least 1 relevant allergic reaction to a non-NACDG allergen. In addition, approximately one-fourth to one-third of reactions detected by NACDG allergens would have been hypothetically missed by T.R.U.E. TEST (SmartPractice Denmark, Hillerød, Denmark).

CONCLUSIONS

These data document the beginning of the epidemic of sensitivity to methylisothiazolinones in North America, which has been well documented in Europe. Patch testing with allergens beyond a standard screening tray is necessary for complete evaluation of occupational and nonoccupational ACD.