**1. Introduction**

Symptomatic management to relieve itchy wheals has been recognized as the standard of care for chronic urticaria. However, around a half of patients with CU are refractory to recommended doses neither an increased doses of antihistamine. In these patients whose urticaria are not controlled with non-sedative antihistamines, more significantly impaired quality of life has been observed. Management guidelines for CU in past included omalizumab, cyclosporine, dapsone, hydroxychloroquine, methotrexate, montelukast, colchine, and phototherapy as alternative treatment for antihistamine-refractory CU [1, 2]. However, most of recent guidelines recommend omalizumab for the first of choice among various immunomodulating agents based on lots of study results [3, 4].

Omalizumab is the only biologics, approved for management of chronic spontaneous urticaria (CSU) in patients at age 12 years or older by Food and Drug Administration (FDA). It a recombinant humanized IgG1, monoclonal anti-IgE antibody. Although the pathophysiology of CU is not completely established, it is clear that mast cell activation is the key feature of CU. Omalizumab binds to free IgE at the Fc region and prohibits IgE from interacting with high-affinity receptor for Fc region of IgE (FcɛRI) on mast cells, basophils and eosinophils [5, 6]. It has been shown to downregulate the expression of FcɛRI on both mast cells and basophils [7]. This chapter reviews the current evidence of the efficacy, safety, and treatment response to biologics targeting IgE, including omalizumab, ligelizumab and quilizumab in CU patients.
