Inclusion Criteria:  Diagnosis of CIU refractory to H1 antihistamines for ≥3 months  Exclusion Criteria:  Chronic urticaria with clearly defined underlying etiology Other skin disease associated with itch Evidence of parasitic infection on stool evaluation for ova and parasites History of anaphylactic shock Hypersensitivity to omalizumab or any component of the formulation Required background therapy with other than protocol-defined antihistamines Any medical condition that could jeopardize or would compromise the patient's safety or ability to participate in this study