The effect of aqueous extract of Sanguisorba officinalis L. (Rosaceae) root (SOAE) on the immediate-type allergic reactions by anal therapy was investigated. SOAE (0.01 to 1 g/kg) dose-dependently inhibited systemic anaphylaxis induced by compound 48/80 in mice. When SOAE was pretreated at the same concentrations with systemic anaphylaxis, the plasma histamine levels were reduced in a dose-dependent manner. SOAE (0.1 and 1 g/kg) also significantly inhibited local anaphylaxis activated by anti-DNP IgE. SOAE (0.001 to 1 mg/ml) dose-dependently inhibited the histamine release from rat peritoneal mast cells (RPMC) activated by compound 48/80 or anti-DNP IgE. The level of cyclic AMP (cAMP) in RPMC, when SOAE (1 mg/ml) was added, transiently and significantly increased compared with that of basal cells. These results provide evidence that anal therapy of SOAE may be beneficial in the treatment of allergic diseases.