Abstract: Objective: To investigate the activation of serum basophils in chronic spontaneous urticaria (CSU) patients. Methods: The expression level of CD63 and CD203c in different time of wheals in CSU patients (group A<2 h，15 cases；group B 12-24 h，15 cases)，after antihistamine therapy (group C，15 cases) and heathy control group (group D,15 cases) was detected by the flow cytometry. Results: The peripheral basophils levels of CSU patients in group A, B and C were 0.097±0.019, 0.072±0.015 and 0.051±0.012, which were higher than that in group D (0.007±0.002，P<0.05). There was no significant  differences between group A, B and C (P>0.05). Conclusion: Activated basophils may be involved in the pathogenesis of CSU, but is associated awith the duration of wheals.

Key words: chronic spontaneous urticaria, basophils, CD63, CD203c