The Effects of Omalizumab (Anti-IgE) on the Late-phase Response to Nasal Allergen Challenge

This research is being done to study the effects of the drug omalizumab (Xolair) in people with cat allergies. The investigators will use omalizumab to study changes in the cells in the nose, cells in the blood and cells in the skin that cause allergies. The investigators will compare the changes in the nose to changes in the skin and blood cells. Objective: To test the hypothesis that treatment with omalizumab will decrease the nasal allergen challenge late-phase eosinophil count in nasal brushings at the time when blood basophils have become hypo-responsive to in vitro allergen exposure.