Increased levels of eosinphils, IgE, IL-4, 5, and 13 and pro-inflammatory factors (COX-2, iNOS) are observed in patients with atopic dermatitis (AD). Taxifolin 3-O-beta-D-glucopyranoside (TAX) from the roots of Rhododendron mucronulatum (RM) was examined to determine whether its immunomodulatory effect was applicable for treating atopic dermatitis.A total of 7 groups of NC/Nga mice with AD were treated by topical application or intraperitoneal injection of TAX for 4 weeks. Follow-up evaluations were done to assess the changes in clinical observations, eosinophil counts, and levels of IgE, cytokines, COX-2 and iNOS.In the clinical observation during the experimental period, TAX treatment significantly reduced the severity of AD-like lesions induced in NC/Nga mice. Eosinophil and IgE levels decreased after treatment of the animals with TAX. TAX may thus be associated with improvement of eosinophil-related allergic diseases. The expression of cytokines (IL-4, 5 and 13) was significantly inhibited in the TAX-treated group, suggesting that TAX might play an immunoregulatory role associated with AD. In RT-PCR, iNOS and COX-2 expression levels were reduced in the TAX-treated group. In western blotting, the expression levels of iNOS and COX-2 were also reduced in the TAX-treated group.These findings suggest that TAX is effective for the treatment of AD by preventing the production of inflammatory cytokines and by reducing skin inflammation.