Objectives : Allergy is an immune dysfunction caused by degranulation from mast cells in the early phase of allergic disease including allergic rhinitis (AR). The purpose of this study was to investigate the effects of Osterici Radix, roots of Ostericum koreanum Maximowicz in human mast cells and experimental allergic animal models. Methods : The anti-allergic effect of Osterici Radix water extract (NK-W) was investigated in human mast cell line, HMC-1 cells, and compound 48/80-induced systemic anaphylactic response in rats and ovalbumin (OVA)-induced AR in mice. Animals were orally administrated with NK-W (10 and 50 mg/kg) or anti-histamine drug, dosodium cromoglycate (50 mg/kg), and then intraperitoneally injected with compound 48/80 (8 mg/kg) or sensitized with 0.1% OVA into nasal. Animals were observed plasma histamine and histological changes of nasal mucosa. Also, mast cell degranulation and histamine production were determined in compound 48/80-stimulated HMC-1 cells. Results : NK-W inhibited compound 48/80-induced degranulation of mast cells and histamine releasing in HMC-1 cells. NK-W decreased mortality and serum histamine releasing in compound 48/80-induced anaphylatic rats in a dose-dependently manner. NK-W also inhibited serum histamine levels in OVA-induced AR mice and improved abnormal histological changes such as expansion of grandular cells and hypertrophy of epithelium in the nasal mucosa. These results indicate that Osterici Radix water extract suppress allergic response through downregulation of mast cell activation. Conclusions : This study suggests that a therapeutic potential of Osterici Radix as a source of anti-allergic agents for use in a number of allergic diseases.