Lithospermi radix (LR, Borraginaceae, the root of Lithospermum erythrorhizon Siebold. et Zuccarinii) is used in herbal medicine to treat such conditions as eczema, skin burns and frostbite. This study investigates the effects of LR on the anti-allergy mechanism. LR inhibited the release of histamine from rat peritoneal mast cells by compound 48/80 in a dose-dependent manner. LR orally administered at 6.59 mg/100 g also inhibited the anti-DNP IgE-induced passive cutaneous anaphylaxis reaction. LR inhibited the PMA plus A23187-induced increase in IL-6, IL-8, and TNF-alpha expression in HMC-1 cells. In addition, LR also inhibited nuclear factor-kappa B (NF-kappaB) activation and I kappaB-alpha degradation. These results show that LR had an inhibitory effect on the atopic allergic reaction. Furthermore, the in vivo and in vitro anti-allergic effect of LR suggests possible therapeutic applications of this agent for inflammatory allergic diseases.