Omalizumab, sold under the brand name Xolair, is a medication used to treat asthma, nasal polyps, and urticaria (hives). Omalizumab is a recombinant DNA-derived humanized IgG1 monoclonal antibody that specifically binds to free human immunoglobulin E (IgE) in the blood and interstitial fluid and to the membrane-bound form of IgE (mIgE) on the surface of mIgE-expressing B lymphocytes. Unlike an ordinary anti-IgE antibody, it does not bind to IgE that is already bound by the high affinity IgE receptor (FcεRI) on the surface of mast cells, basophils, and antigen-presenting dendritic cells. Medical uses In the United States, omalizumab is indicated to treat moderate to severe persistent asthma, nasal polyps, and chronic idiopathic urticaria. In the European Union, omalizumab is indicated to treat allergic asthma, chronic (long-term) spontaneous urticaria (itchy rash), and severe chronic rhinosinusitis with nasal polyps. In Australia, omalizumab is indicated to treat allergic asthma and chronic spontaneous urticaria. Allergic asthma Omalizumab is used to treat people with severe, persistent allergic asthma, uncontrollable with oral or injectable corticosteroids. Those patients have already failed step I to step IV treatments and are in step V of treatment. Such a treatment scheme is consistent with the widely adopted guidelines for the management and prevention of asthma, issued by Global Initiative of Asthma (GINA), which was a medical guidelines organization launched in 1993 in collaboration with the National Heart, Lung, and Blood Institute, National Institutes of Health, USA, and the World Health Organization. Chronic spontaneous urticaria Omalizumab is indicated for chronic spontaneous urticaria in adults and adolescents (>12 years old) poorly responsive to H1-antihistamine therapy. When administered subcutaneously once every four weeks, omalizumab has been shown to significantly decrease itch severity and hive count. Adverse effects The main adverse effect is anaphylaxis (a life-threatening systemic allergic reaction), with a rate of occurrence of 1 to 2 patients per 1,000. Limited studies are available to confirm whether omalizumab increases the risk of developing cardiovascular (CV) or cerebrovascular disease (CBV). Cohort and randomised controlled studies have shown that the risk of developing CV/CBV disease is around 20-32% higher in patients taking omalizumab compared to those not taking omalizumab. Additional multi-national, longitudinal studies with increased subject numbers are required to provide further clarification into the relationship and clinical significance between omalizumab and CV/CBV disease. Due to the severity of CV/CBVs side effects, clinicians and health care providers should continue to remain vigilant and monitor side