Chronic spontaneous urticaria (CSU) is defined as itchy hives with or without angioedema with a burning sensation that last for six weeks or longer and have no apparent external trigger. The disease occurs in about 1 % of the population. The itching and burning symptoms affect the patient’s quality of life in a negative way which makes a treatment highly needed. The first-line medication for the treatment of CSU is non-sedating H1-antihistamines in recommended doses and the second line of treatment is an increased dose of H1-antihistamines, up to four-fold the approved doses. However, many patients do not response to these therapies whereas a third-line treatment, an add-on therapy with omalizumab, is necessary. Omalizumab is a monoclonal anti-IgE-antibody that binds to free IgE and prevents them to attach to FcεRI-receptors on inflammatory cells like mast cells. This leads to a lower activation of mast cells and less histamine gets released. The definite mechanism of action of CSU-symptoms relief is still unclear but it is thought to be due to decreased levels of IgE and FcεRI-receptors. The symptoms of CSU can be scored using weekly itch severity score (ISS7) which scores the pruritus, weekly hive severity score (HSS7) which scores the number of hives and weekly urticaria activity score (UAS7) that scores both pruritus and number of hives together. The aim of this literature review was to evaluate the efficacy and safety of omalizumab in patients diagnosed with CSU. A search on PubMed was conducted with the search terms "omalizumab" AND "chronic spontaneous urticaria" and "omalizumab" AND "chronic idiopathic urticaria". The articles were limited to randomized, controlled and double-blinded trials that were published 2010 or later. A total of five studies were included for further analysis; MYSTIQUE, ASTERIA II, ASTERIA I, POLARIS and GLACIAL. The studies showed that omalizumab 300 mg and 150 mg reduced the symptoms of CSU significantly compared with placebo, whereas 300 mg had the best efficacy in decreasing the values of ISS7, HSS7 and UAS7. The patients went from having severe urticaria to mild urticaria after treatment with omalizumab. The degree of itching improved from severe itching to mild itching. The side effects were mild to moderate, the most common were nasopharyngitis, headache, arthralgia and upper respiratory tract infection. Omalizumab showed to be effective and safe as an add-on therapy for the treatment of patients with chronic spontaneous urticaria who did not respond adequately to treatment with H1-antihistamines.