Diazolidinyl urea: incidence of sensitivity, patterns of cross-reactivity and clinical relevance.

Diazolidinyl urea (DIAZ) is a formaldehyde-releasing preservative used in cosmetics and personal-care products, which has been identified as a sensitizing agent in contact dermatitis. To determine whether DIAZ sensitization is secondary to formaldehyde release or due to its own allergenic properties, we reviewed 708 consecutive patch tests of patients with various dermatologic complaints. Profiles of the 58 individuals (8%) with DIAZ sensitivity were analyzed with respect to sex, age, exposures, and chronicity of dermatitis. Significant coexistent biocide reactivity was demonstrated for DIAZ and formaldehyde (81%); 12% reacted to DIAZ alone. We conclude that the primary mode of sensitization of DIAZ is via formaldehyde release and that independent contact allergy is less frequent.