Efficacy and safety of modified Xiao-Feng Powder in the treatment of chronic urticaria: protocol of a randomized double-blind placebo-controlled study oleh Hing Yu Hung, Tianhe Song, Steven King Fan Loo, Kam Leung Chan, Jessica Yuet Ling Ching, Chi Him Sum, Louis Cho Wing Lo, Sarah Chon Pin Chia, Ray Tin Muk Ho, Pui Kuan Cheong, Tony Hon Chung Siu, Ka Chun Leung, Zhi-Xiu Lin