This is a humanized IgG1 monoclonal antibody using the same sequences as the therapeutic antibody omalizumab. It is against human immunoglobulin E (IgE), and effectively treats severe persistent allergic forms of asthma, nasal polyps, chronic idiopathic urticaria and IgE-mediated food allergy by limiting the allergic response. Omalizumab specifically binds to free human IgE in both blood and interstitial fluid, as well as to the membrane-bound form of IgE (mIgE) expressed on B lymphocytes surface. By inhibiting the binding between IgE and receptors on mast cells and basophils, it blocks the release of inflammatory mediators triggered by IgE. Omalizumab does not bind to IgE that is already occupied by the high affinity IgE receptor on mast cells, basophils or antigen-presenting dendritic cells.