* Omalizumab is a recombinant humanised monoclonal antibody which specifically binds to the C epsilon3 domain of immunoglobulin (Ig) E, the site of high-affinity IgE receptor binding. * Improvements in asthma symptoms and health-related quality-of-life, and a significant reduction in the frequency of asthma exacerbations were seen in allergic asthmatic patients treated with omalizumab. * Omalizumab was also effective in the treatment of children with allergic asthma demonstrating improvements in health-related quality-of-life and significant dosage reductions of inhaled corticosteroids. * Administration of omalizumab to patients with allergic rhinitis resulted in a rapid dose-dependent suppression of serum free IgE levels. * Omalizumab significantly improved health-related quality-of-life and nasal symptoms in patients with seasonal allergic rhinitis. Antihistamine requirements were also significantly reduced following treatment. * Adverse events were infrequent in clinical trials of omalizumab, and not significantly different from placebo. The most frequent drug-related event was mild to moderate urticaria.