Comparison of patch test results with a standard series among white and black racial groups

Background: Environmental, cultural, occupational, genetic, individual, and racial differences are important factors in the study of contact dermatitis. Some epidemiologic studies have compared overall sensitization rates among different racial groups, but similar data are lacking on individual allergens. Objective: Determine differences in sensitization rates between 2 racial groups in North America undergoing patch testing over a period of 4 years at the Cleveland Clinic Foundation (CCF), Ohio. Methods: Retrospective computer review of the standard screening tray results of 991 patients with an average age of 45.9 years consisting of 877 (88.5%) whites and 114 (11.5%) blacks. Results: Nickel sulfate and thiomersal (both 8.0%) and nickel sulfate and p-phenylenediamine (both 10.6%) were the 2 most common sensitizers among whites and blacks respectively. There was a statistically significant difference (P = .00599) in the sensitization rate for p-phenylenediamine in blacks (10.6%) compared with whites (4.5%). There were also statistically significant differences in sensitization rates for p-phenylenediamine (21.2%; P = .00005) and imidazolidinyl urea in petrolatum (pet.) (9.1%; P = .04103) in black men compared with white men (p-phenylenediamine [4.2%] and imidazolidinyl urea [2.6% pet.]). Conclusion: The differences in sensitization rates, especially for p-phenylenediamine, may reflect variations in allergen exposure among racial groups or interindividual variations in the N-acetylation (N-acetyltransferase 1 [NAT1] and 2 [NAT2]) capacities of human skin for p-phenylenediamine.