The role of contact allergens in chronic idiopathic urticaria.

Objective: The objective of this study was to determine whether contact allergens play a role in chronic idiopathic urticaria (CIU).

Methods: We conducted a longitudinal prospective study of 23 patients with CIU. Patients were patch tested to a modified North American Contact Dermatitis Group standard, fragrance, and cosmetic series; other series were tested as warranted by relevant history and physical examination. Readings were performed at 48 and 72 hours. Patients were counseled to avoid proven contact allergens and were followed up 2 to 9 months after testing.

Results: Twenty-one of 23 patients were female. The mean age was 46 years. The mean duration of urticaria was 32 months. Of the 23 patients, 8 (35%) experienced improvement of their symptoms with allergen avoidance. Four (17%) experienced a complete remission, and 4 (17%) experienced partial improvement. Two of the complete responders challenged themselves to proven contact allergens and developed urticaria, which resolved upon allergen avoidance. The most common allergens were potassium dichromate (n = 9), nickel sulfate (n = 7), Myroxylon pereirae (n = 6), cobalt chloride, neomycin, p-phenylenediamine (n = 5); fragrance mix I, fragrance mix II (n = 4); cinnamic aldehyde (n = 3); and formaldehyde (n = 2).

Conclusions: Patch testing may be helpful in the evaluation of CIU patients for whom previous workup has failed to reveal an etiology.