Summary Monoclonal anti-IgE antibodies (omalizumab) are able to induce clinically significant benefits in patients with severe chronic spontaneous urticaria (CS). Those results led clinicians and investigators to reconsider a possible pathogenic role not previously supported for IgE and its receptors in this disease, and to investigate additional approaches for understanding its pathogenesis. IgE antibodies to unknown environmental allergens able to trigger chronic urticaria are not generally regarded as the etiologic factor for the disease. Other proposed mechanisms for the production of wheals and angioedema in CSU include IgG autoantibodies and CD4-positive T cells directed to the high-affinity