Regional variation in prevalence and etiology of allergic contact dermatitis

Background: The 1994-1996 North American Contact Dermatitis Group (NACDG) patch test results were the first, since the inception of the NACDG in 1970, to include results from a medium-sized metropolitan city in the Midwest. Objective: The aim of this study was to determine whether the causative allergens of allergic contact dermatitis (ACD) in the Midwest differ from those in other regions of the United States and, if so, whether occupational or other factors account for the observed differences. Methods: Retrospective analyses of patch test data collected at the University of Kansas Medical Center (Kansas City, KS) were compared with the data collected by the other NACDG centers. Results: Patients in Kansas City were statistically more likely to react to potassium dichromate, formaldehyde and its releasers, methylchloroisothiazolinone/methylisothiazolinone (MCI/MI), and glutaraldehyde. Occupational exposures to chromium and formaldehyde were increased significantly among patients from Kansas City, although the percentages of the local population engaged in these occupations did not differ from those in other NACDG cities. Equal percentages of workers in Kansas City and nationally had occupationally related allergy to glutaraldehyde, although the overall rate of glutaraldehyde was higher among patients from Kansas City. Most cases of relevant allergy to MCI/MI were cosmetically induced both in Kansas City and nationally. Conclusions: The current findings show significant regional differences in causal allergens. The increased percentages of patients seen with ACD to formaldehyde, formaldehyde-releasing agents, and potassium dichromate in Kansas City were likely caused by the referral of greater numbers of work-related cases. However, occupationally acquired ACD to MCI/MI and glutaraldehyde were not more frequent in Kansas City than nationally, suggesting that other factors might be operative. Although awareness of national trends is important, dermatologists must be cognizant of regional variations in allergen sources within their communities and referral networks.