Contact allergens in oral antihistamines.

Background: Excipients in various formulations of active drugs occasionally include known contact allergens. Their ingestion may trigger dermatitis or cause it to become widespread or refractory to therapy.
Objective: The aim of this study was to investigate the prevalence of common contact allergens among the excipients of oral antihistamines available in this country.
Methods: We gathered the complete ingredient lists of 2119 different preparations of 12 oral antihistamines from the National Library of Medicine data bank and entered them into an electronic database for analysis.
Results: More than half the formulations (55.0%) contained at least 1 member of the 10 allergen families assessed. Most brompheniramine and doxepin preparations included potentially allergenic excipients, whereas fexofenadine was most often free of them. Sorbitan group members, azo dyes, and propylene glycol were the allergens found most frequently in the antihistamines, each present in over 25% of the products. Elixirs, liquids, solutions, suspensions, and syrups were more likely than nonchewable caplets, capsules, and tablets to contain the allergens tabulated (100% vs 39.3%, respectively). Chewable pills frequently contained azo dyes.
Conclusions: Ingestion of antihistamines could precipitate a systemic contact dermatitis in a patient sensitized to an allergen present as an excipient in the medicine.