This is a Phase IV, single-site study that will examine blood cells or tissue obtained from CIU patients receiving open-label treatment with omalizumab at the current FDA-approved dose of 300 mg/month for 12 weeks in addition to standard therapy with anti-histamines. Results from the 3 Phase III studies in CIU patients provide evidence that a meaningful change in symptoms is apparent at 1-2 wks. The MID (Minimal Important Difference) is achieved by 70% of patients by 2 wks on multiple background drugs for hives. The goal is to identity the IgE bearing cell type associated with clinical symptom change.