We describe a case of chronic idiopathic urticaria in which symptoms improved dramatically after treatment with omalizumab. This drug, which is approved for the treatment of asthma, has been studied in other allergic conditions and a number of reports have described its efficacy as an immunomodulator in chronic and physical urticaria.
Immunopathologic mechanisms are poorly understood. In chronic autoimmune urticaria, it has been postulated that this monoclonal antibody against immunoglobulin (Ig) E might reduce FcεRI expression on the surface of basophils, thus preventing IgG antibody-mediated crosslinking and the release of mast cell mediators.
We analyzed activation and homing molecules of B cells and type 1 and type 2 cytokine production by T cells and document a new immunomodulator mechanism characterized by a reduction in B-cell activation and homing and in tumor necrosis factor-α and interleukin 4 production and an increase in interferon-γ synthesis.

Key words: Chronic urticaria. Anti IgE. Omalizumab. B cell.