Allergic contact dermatitis caused by idoxuridine. Patterns of cross reactivity with other pyrimidine analogues.

Idoxuridine has been used for many years in the treatment of herpex simplex infections of the eye. Use of the drug for herpes simplex infection of the skin is increasing. Ophthalmologists have noted occasional conjunctival and corneal irritant reactions, but no true delayed cutaneous hypersensitivity has been verified. We report four cases of allergic contact dermatitis from idoxuridine, sensitized by both eye and skin applications. Cross reactivity to brominated and chlorinated, but not fluorinated, pyrimidine analogues is noted. Extensive patch testing indicates the general relationship between the structure of pyrimidine compounds and their antigenic cross reactivity.