Addition of omalizumab + dexamethasone SD proved an improvement in histamine airway hyperresponsiveness and caused an increase in the bronchorelaxant effect of isoprenaline in the sensitized guine pigs. Whereas, omalizumab alone did not give these effects. Omalizumab when used alone or combined to dexamethasone SD, caused a decrease in both inflammatory cells: eosinophils and lymphocytes. This may show an anti-inflammatory effect for omalizumab. Taken together, these results extended those previously reported regarding the efficacy of omalizumab. Omalizumab as an add-on therapy to corticosteroids in patients with severe asthma on high-dose coticosteroids succeeded to reduce the dose of corticosteroid. This steroid-sparing effect may be of extreme benefit to decrease the adverse effects of corticosteroids. On the other hand, omalizumab caused linear haemorrhagic lesions and mucosal erosions in the gastric mucosa. Also, it exaggerated the response of the gastric mucosa to cold-stress. Moreover, Omalizumab + dexamethasone SD worsened the erosions of the gastric mucosa induced by cold-stress. Therefore, further assessment of the safety profile of omalizumab is mandatory.