Approximately 45% of patients with chronic urticaria have an IgG autoantibody directed to the ⍺-subunit of the high-affinity IgE receptor (chronic autoimmune urticaria, CAU) leading to cutaneous mast cell and basophil activation. Treatment of allergic asthma with omalizumab produces rapid reduction in free IgE levels and subsequent decrease in FcRI expression on mast cells and basophils. If this occurs in CAU, cross-linking of IgE receptors by autoantibody would be less likely, reducing cell activation and urticaria/angioedema.

To investigate the efficacy of omalizumab in patients with CAU symptomatic despite antihistamine therapy.

Twelve patients with CAU, identified by basophil histamine release assay and autologous skin test, with persistent symptoms for at least 6 weeks despite antihistamines, were treated with placebo for 4 weeks followed by omalizumab (≥0.016mg/kg/IU mL^-1 IgE per month) every 2 or 4 weeks for 16 weeks. Primary efficacy variable was change from baseline to the final 4 weeks of omalizumab treatment in mean Urticaria Activity Score (UAS, 0-9 scale). Changes in rescue medication use and quality of life were assessed.

Mean UAS declined significantly from baseline to the final 4 weeks of omalizumab treatment (7.50 ± 1.78 to 2.66 ± 3.31, -4.84 ± 2.86, P = .0002). Seven patients achieved complete symptom resolution. In 4 patients, mean UAS decreased, but urticaria persisted. One patient did not respond. Rescue medication use was reduced significantly, and quality of life improved. No adverse effects were reported or observed.

This exploratory proof of concept study suggests omalizumab is an effective therapy for CAU resistant to antihistamines.