A retrospective study of 2585 patients patch tested with the European standard series in Hong Kong (1995-99).

Background: Data on patch test findings in Hong Kong are scarce, with the last survey performed more than 10 years ago. A retrospective analysis of results from all patch tests performed on patients with suspected allergic contact dermatitis from January 1995 to December 1999 in the Social Hygiene Service, which provides a public dermatology service in Hong Kong, was undertaken. We aimed to explore the demographic data associated with positive reactions and the profile of contact sensitizing allergens in Hong Kong.

Methods: A total of 2585 patients were patch tested with the European standard series during the period. Most were Chinese, with a female-to-male ratio of 3 : 2.

Results: One or more positive responses were noted in 1415 patients (54.7%). The most common allergen was nickel sulfate (24.4%), followed by fragrance mix (13.7%), cobalt chloride (8.7%), p-phenylenediamine (6.0%), and balsam of Peru (5.7%). Nickel sensitivity was more common in female patients, and dichromate sensitivity was more common in male patients (P < 0.001). Female gender, an age of 40 years or below, truncal and upper limb involvement, absence of lower limb involvement, and a positive atopy history were significant risk factors for nickel sensitivity.

Conclusions: This study provides a profile of allergens responsible for allergic contact dermatitis in the public dermatology service in Hong Kong. A prospective study, using a larger panel of allergens, involving patients from both the private and public sectors, would provide a more comprehensive profile of contact allergens in Hong Kong and contribute to the establishment of a local standard series.