In order to test the above hypothesis, the investigators propose a placebo controlled, double blind, parallel group study to obtain proof of principle that omalizumab exerts beneficial effects on disease control in non-atopic severe adult asthmatics aged 18-60 years . Forty patients will be randomized in a 1:1 ratio to receive omalizumab or matching placebo. Following 12 weeks of treatment with omalizumab/placebo, and as this treatment is continued for a further 8 weeks, anti-asthma treatment will be reduced. Dosages will be administered at 4 or 2 weekly intervals over a 16 week period (5 or 10 doses in total), which corresponds with the time stated as necessary to judge efficacy of therapy according to omalizumab's licensed indications in atopic asthma. Efficacy will be judged by clinical monitoring and by bronchial biopsy to assess effects on bronchial inflammation and local IgE production.