Group A: With omalizumab treatment for 6 months; dosage and administration schedule according to body weight and total IgE level (1/2 of the patients). Group B: Placebo (1/2 of the patients). After 4 months of treatment in both groups patients are encouraged to stop all drugs given to reduce mast cell related effects, mainly antihistaminics . In case that disturbing symptoms are reoccurring patients are allowed to restart these drugs. The evaluation will take place after 5 months of treatment.