Prevalence of contact allergy at a dermatology clinic in China from 1990-2009.

Background: The prevalence of contact allergy varies in different regions and populations. Objective: To describe the frequency of sensitization in patients with dermatitis or eczema referred to Peking University First Hospital and analyze the trends in the prevalence of common allergens from January 1, 1990, to December 31, 2009. Methods: A total of 1,858 patients were patch tested with the Chinese baseline series of contact allergens. Data were collected from retrospective charts and analyzed. Results: Positive reactions to one or more allergens were shown in 1,374 patients (74.0%). The most common sensitizers were nickel sulfate (25.7%), fragrance mix I (25.6%), thiuram mix (25.5%), ammoniated mercury (20.5%), and p-phenylenediamine (19.1%). A statistically significant increase of sensitization over the 20-year period was seen for nickel sulfate, fragrance mix, ammoniated mercury, colophony, ethylenediamine, and potassium dichromate. Mercapto mix showed a trend of a statistically significant decrease in sensitizations from 1990 to 2009. Conclusions: The patterns of contact allergy in patients from Peking University Hospital are different from those of patients in other regions of China, in European countries, and in the United States. Nickel and fragrance mix were the most common allergens, and the sensitization rates of these two allergens had been increasing remarkably during the 20 years from 1990 to 2009.