The purpose of this study is to look at the effectiveness of Xolair® (omalizumab) in people with asthma taking Advair Diskus®. The study will look at the effects of Xolair® on lung function using high resolution computed tomography (HRCT) scans after asthma symptoms are induced with a special substance called methacholine. This study is only taking place at UCLA, where about 13 subjects will be enrolled. Participation requires 10-14 visits over about 26 weeks.