An epidemic of allergic contact dermatitis caused by a new allergen, caprylhydroxamic acid, in moisturizers.

Background. In 2016, dermatologists in Finland suspected contact allergy in several patients using moisturizers under the trade name Apobase (R). Following a formulation change, Phenostat (TM), which is a mixture of phenoxyethanol, caprylhydroxamic acid, and methylpropanediol, was used as a preservative in Apobase (R) moisturizers in Finland. Objectives. To confirm the suspected contact allergy to Apobase (R) cream, oily cream, and/or lotion, and to identify the specific contact allergen and define its optimal patch test concentration. Methods. Thirty-nine patients with suspected contact allergy to Apobase (R) creams or lotion were patch tested in four Finnish dermatological clinics. The patch tests included old and new Apobase (R) formulas and their preservative agents: phenoxyethanol, methylpropanediol, and dilution series of Phenostat (TM) and caprylhydroxamic acid or its potassium salt. Results. The patch tests showed positive reactions to the new Apobase (R) formulas, Phenostat (TM), and caprylhydroxamic acid or its potassium salt, but not to the old Apobase (R) formulas, methylpropanediol, or phenoxyethanol. Conclusions. We found a new contact allergen, caprylhydroxyamic acid, which caused an epidemic of allergic contact dermatitis in patients using moisturizers containing this preservative. Whether the sensitizing capacity of caprylhydroxamic acid depends on the other chemicals used in Apobase (R) moisturizers needs further investigation.