Contact dermatitis from thimerosal.

Thimerosal, synthesized from ethylmercuric chloride and thiosalicylic acid is, besides nickel, one of the two most frequent contact allergens. Recently, ethylmercuric chloride has been reported to be the responsible agent in thimerosal hypersensitivity. On routine patch testing, a high incidence of positive patch test reactions to thimerosal was observed, although in most cases, patients neither showed nor reported symptoms that could be related to thimerosal. The aim of the present study was to evaluate the frequency and relevance of positive patch test reactions to thimerosal, as well as to its two components, ethylmercuric chloride and thiosalicylic acid and to correlate these results with the particular diagnoses of patients.