Objective:To study the effect of Jumihaidokuto (Shi-Wei-Bai-Du-Tang,十味败毒汤) in the management of chronic spontaneous urticaria.Methods:A randomized two-arm,parallel group study was conducted to compare the effect of Jumihaidokuto (6 g daily) with a control for 8 weeks.Concomitant therapy (e.g.,antihistamines) was continued.Twenty-one subjects with severe chronic urticaria were enrolled in this study.The primary treatment outcome was the severity score proposed by the Japanese Dermatological Association.Secondary outcomes were quality of life (Skindex-16),itch intensity (Visual Analogue Scale),and patients\' subjective disability due to wheal or itch.After the subjects were randomly assigned to groups by block randomization,10 received Jumihaidokuto,and 11 did not.All subjects had already taken antihistamines.Results:Improvement was significant when comparing the severity score of the Jumihaidokuto group with that of the control group (P＜0.01).Skindex-16 values for both groups gradually decreased in the same fashion.Conclusion:Concomitant use of Jumihaidokuto with antihistamine was more effective than antihistamine alone in the management of chronic idiopathic urticaria.