Topical cis-urocanic acid suppresses both induction and elicitation of contact hypersensitivity in BALB/C mice.

Cis-urocanic acid, converted from trans-urocanic acid in stratum corneum by ultraviolet B irradiation, has been shown to impair contact hypersensitivity induction. To study whether topical cis-urocanic acid also alters contact hypersensitivity elicitation, as well as immediate hypersensitivity and acute irritation, we treated mice with 1% topical cis-urocanic acid or vehicle prior to induction or elicitation of hypersensitivity to contact allergen oxazolone or respiratory allergen trimellitic anhydride or prior to acute irritation from croton oil. Topical cis-urocanic acid suppressed both induction and elicitation of contact hypersensitivity to oxazolone. However, no effect by cis-urocanic acid on induction or elicitation of trimellitic anhydride allergy or croton oil irritation was seen. The possible efficacy of topical cis-urocanic acid as a treatment of inflammatory skin diseases responsive to ultraviolet B irradiation may be worthwhile to investigate.