Objective: To study the effects and pharmacological mechanism of anti-type-I hypersensitivity of Guizhi Jia Gegen Tang(GGT). Method: Mice were randomized into six groups

the control

chlorpheniramine

dehydrocortisone and low

moderate

high dosage of GGT. Using the type- I hypersensitivity animal model

the effects of six groups on the passive cutaneous hypersensitivity and capillary permeability were compared. Result: Administration of GGT attenuated significantly the diameter of blue plaque induced by the anti-serum with different dilution(P<0.01)

of which both the moderate and high dosage of GGT have similar potency of chlorpheniramine. The increase of capillary permeability induced by 5-hydroxytryptamine or histamine and the voix pedis swell evoked by histamine were counteracted by all the three dosages of GGT (P<0.01) alike chlorpheniramine. Conclusion: The antagonism against the mediators of inflammation may contributed to the anti-type-I hypersensitivity of GGT.