Xolair, generically known as omalizumab, is a prescription medication designed for the treatment of moderate to severe persistent asthma in patients who have had an inadequate response to inhaled corticosteroids. It is also approved for use in individuals with chronic idiopathic urticaria (CIU), a form of chronic hives without a known cause, who do not respond to antihistamines. Xolair works by targeting and blocking immunoglobulin E (IgE), a type of antibody in the body that plays a key role in the allergic response. By inhibiting the action of IgE, Xolair helps reduce the number of asthma attacks and alleviate the symptoms of CIU. It is administered through injections under the skin (subcutaneously) and is typically prescribed by specialists in allergy and immunology.