BACKGROUND: Atranol and chloroatranol are the main allergens of oakmoss absolute. However, the immune responses induced by these substances are poorly characterized.

OBJECTIVES: To characterize immune responses induced by atranol, chloroatranol and oakmoss absolute in mice.

METHODS: Mice were sensitized and challenged with various concentrations of atranol, chloroatranol, and oakmoss absolute. The immune responses were analysed as B cell infiltration, T cell proliferation in the draining lymph nodes, and expression of interleukin (IL)-18, IL-1β and tumour necrosis factor-α in skin. The cytotoxicity of atranol and chloroatranol against keratinocytes was determined.

RESULTS: Sensitization experiments showed that atranol, chloroatranol and oakmoss induced sensitization when applied in high concentrations. Challenge experiments showed that even low concentrations of atranol and chloroatranol induced sensitization. In parallel, atranol and chloroatranol elicited challenge reactions following sensitization with oakmoss. The magnitude of the immune response to the three allergens increased in the following order: atranol, chloroatranol, and oakmoss. The expression of proinflammatory cytokines was induced by chloroatranol and oakmoss, but not by atranol. Chloroatranol was found to be more cytotoxic than atranol against keratinocytes.

CONCLUSIONS: Atranol and chloroatranol can elicit both sensitization and challenge reactions, but the mixture of allergens in oakmoss absolute is more potent than atranol and chloroatranol alone.