The effect of aqueous extract of processed Xanthii fructus (PXF) on cell viability and histaminerelease from mast cell has been investigated. PXF showed higher cell viability than unprocessedXanthii fructus (XF) at the concentrations of 5 and 10 mg/ml. Aqueous extract of PXF andunprocessed XF inhibited compound 48/80-induced systemic anaphylaxis in mouse. Both PXFand unprocessed XF dose-dependently inhibited histamine release from rat peritoneal mast cellsby compound 48/80 to the similar extent at 0.01, 0.1 and 1 mg/ml. Our studies provide evidencethat processing of XF may be beneficial to reduce cytotoxicity in high concentration (at 5 and 10mg/ml) but does not affect on anti-allergic activity.