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