n. a *monoclonal antibody used in the prevention of severe allergic asthma that has not responded to standard therapy and is also a highly effective treatment for chronic *urticaria. It is now recommended by NICE as an additional treatment to standard asthma therapy for some people aged six years and over with severe persistent allergic asthma. Omalizumab acts by binding to IgE, an *immunoglobulin that mediates the allergic response.