Objective:To evaluate the efficacy and safety of desloratadine in the treatment of acute and chronic idiopathic urticaria in comparison with loratadine.Methods:A multicenter,double blind,double dummy,randomized,parallel group study was performed.197 patients were randomly divided into the desloratadine group( n =99) to receive desloratadine 5 mg,qd and the loratadine group( n =98) to receive loratadine 10 mg,qd,for 1 week to acute urticaria and 2 weeks to chronic idiopathic urticaria.Results:At the end of treatment, the effective rates of the desloratadine group and the loratadine group were 84.85% and 84.69% respectively,the clinical cure rate were 69.7% and 64.29% respectively. There was no significantly statistical difference between two groups ( P =0.499). Both of the antihistamines had no effects on hepatic and renal function or on electrocardiographic parameters.Conclusion:Desloratadine made in China is safe and effective in the treatment of acute and chronic idiopathic urticaria,and the efficacy of 5mg·d -1 desloratadine is equal to 10mg·d -1 loratadine.