We examined the effects of essential oil from Thujopsis dolobrata Sieb. et Zucc. var. hondai Makino (EOTD) (Cupressaceae) on atopic dermatitis (AD)-like skin lesions in NC/Nga mice. Treatment with EOTD twice daily for two weeks ameliorate AD-like skin lesions induced by DNCB (2,4 dinitrochlorobenzene), and clinical scores were reduced to 7.29, 7.07, and 4.5 points in the groups treated with 1.5%, 3.0%, and 6.0% extract (p<0.01) respectively, from the 15.0 score obtained using vehicle. EOTD inhibited the infiltration of mast cells into the AD-like skin lesion in NC/Nga mice (p<0.01) and also reduced serum histamine and IgE levels (p<0.05). Furthermore, it dose-dependently inhibited the release of beta-hexosaminidase from rat basophilic leukemia RBL 2H3 cells. These results indicate that EOTD reduces AD-like skin lesions by inhibiting the production of IgE and histamine, and, thus, IgE-mediated degranulation.