Chronic spontaneous urticaria is defined as recurrent wheals of unknown etiology for more than 6 weeks,with or without angioneurotic edema.The key step in the pathogenesis of chronic spontaneous urticaria is activation and degranulation of mast cells and basophils.Omalizumab,a recombinant humanized IgG monoclonal antibody,can selectively bond the Fc region of free IgE antibodies,and then block IgE-FCeR Ⅰ-mediated activation of mast cells and basophils.Three phase Ⅲ clinical trials have been reported on the efficacy of omalizumab in the treatment of chronic spontaneous urticaria,which confirm the efficacy and safety of omalizumab in the treatment of refractory chronic spontaneous urticaria.