Allergie contact dermatitis to preservatives in topical medicaments

Background: Formaldehyde-releasing preservatives are well-known allergens found in many topical preparations including medications. Objective: To analyze the relevance of a positive patch test to formaldehyde-releasing preservatives in medications containing these preservatives. Methods: Patients were recruited with a history of allergy to one of these preservatives. Patch and use testing to the medications, vehicles, and preservatives were performed. The following medications and their respective preservatives were used: Rénova 0.05% cream/quaternium-15, Dovonex 0.005% cream/diazolidinyl urea, and Temovate-E 0.05% cream/diazolidinyl urea. Results: Nine patients participated in the study. A positive patch test to the preservative was repro-duced in six of nine patients, and a questionable reaction occurred in one. Two patients had a positive patch test to the topical medication and one a questionable reaction. There were no definitive positive patch tests to the vehicle but two questionable ones. Use testing revealed three positive reactions to Rénova, one to Rénova vehicle, and one to Temovate-E vehicle. Conclusions: The concentration of the preservative in the commercial preparation was often below the threshold necessary to produce a clinical reaction. Use testing is a valuable tool in the complete evaluation of the patient with a positive patch test to a formaldehyde-releasing perservative found in topical medication. Copyright