Objective:To evaluate the anti-histamine and anti-arachidonic acid potency of mizolastine,loratadine and cetirizine.Methods:The inflammatory edema reaction of rat paw was induced by a subcutaneous injection of arachidonic acid(1.0 g/L,0.1 mL)and histamine(10 g/L,0.1 mL)respectively.Mizolastine(0.6 mg/kg),loratadine(0.6 mg/kg)or cetirizine(0.6 mg/kg)were given orally 2 hours before the injection.The swelling volumes of rat paw were measured plethysmographically and compared at the different time points after the administrations,respectively.Results:Mizolastine inhibited arachidonic acid induced paw edema reaction significantly(P < 0.05).No significant inhibitory effects were found after administration of loratadine and cetirizine.Mizolastine inhibited histamine induced paw edema reaction significantly(P < 0.05),and its effects was stronger than those of loratadine,but had no significant difference compared with cetirizine(P > 0.05).Conclusions:Mizolastine shows a dual potency in anti-histamine and anti-arachidonic acid activities.It exerts a higher anti-histamine effect than loratadine.Compared with loratadine and cetirizine,Mizolastine displays unique anti-arachidonic acid activity.