Given the efficacy of omalizumab in the treatment of moderate to severe allergic asthma, the researchers will conduct a double-blind study to evaluate the safety and efficacy of omalizumab in a small number of patients with chronic urticaria with persistent symptoms in spite of background antihistamine therapy. Omalizumab is currently not indicated for patients with chronic urticaria. The primary hypothesis is that omalizumab will lead to a reduction in serum IgE levels and blood basophil high affinity IgE receptor expression in subjects with chronic idiopathic urticaria. Additionally, clinical outcomes such as quality of life, symptoms scores, and medication use will be explored. This study should allow for further understanding of the role IgE plays in chronic urticaria.