Mitigation of stress-induced suppression of contact hypersensitivity by odorant inhalation

Background Various skin functions are affected by stress. We have previously shown that odorant inhalation can regulate skin immune reactions. Objectives To test the hypothesis that certain odorants can mitigate the effects of stress on skin immune reactions. Methods Contact hypersensitivity (CH) reactions were elicited in C57BL/6 mice. Mice were subjected to immobilization stress and were exposed to odorants for 2 days. Epidermal sheets were stained for I‐A antigens and analysed by confocal laser scanning microscopy. Serum corticosterone levels were assayed by radioimmunoassay. Results Exposure of mice to 1,3‐dimethoxy‐5‐methylbenzene (DMMB) had no effect on the intact CH reaction, but it upregulated the reaction suppressed by immobilization stress. Other odorants, including terpinyl acetate and valerian oil, had minor effects on the CH reaction. Suppression of I‐A‐positive cells was prevented by DMMB inhalation. Valerian oil, but not DMMB, downregulated stress‐induced plasma corticosterone levels. Conclusions Results suggest that odorant inhalation modulates various physiological pathways, some of which result in regulation of skin function.