Topical royal jelly alleviates symptoms of pruritus in a murine model of allergic contact dermatitis

Background: Royal jelly is widely used as a health tonic, especially in Asia. Royal jelly is commonly used in cosmetics as well as in dietary supplements and beverages. Little is known, however, about the pharmacologic efficacy of topical royal jelly. Therefore, we investigated the antipruritic activity of topical royal jelly on chronic pruritus in experimental allergic contact dermatitis in mice. Materials and Methods: Hairless mice (HOS: HR-1), with chronic allergic contact dermatitis induced by 5 weeks of repeated application of 2,4,6-trinitro-1-chlorobenzene (TNCB) to the entire back skin were treated topically with royal jelly (0.01% or 1%) for 5 weeks after sensitization with TNCB. The effects of royal jelly on pruritus and inflammation were evaluated by measurement of scratching behavior and skin inflammation score, respectively. Results: Repeated application of TNCB to the back skin of mice elicited frequent scratching behavior immediately and 24h after challenge. Topical royal jelly (0.01% or 1%) and betamethasone (0.01%) significantly ameliorated this chronic pruritus throughout the experimental period. The level of nerve growth factor mRNA in back skin was increased in the mice with dermatitis and reduced by betamethasone, but not by royal jelly. Conclusion: The inhibitory effect of royal jelly on chronic pruritus may occur through different mechanisms from those of betamethasone. Topical application of royal jelly, as used in cosmetics, might be beneficial for the alleviation of chronic pruritus.