The present study would allow to offer to the Health System an evidence to evaluate the convenience or not to approve the use of Omalizumab for the new indication of chronic urticaria treatment. It is important to take into account that in the present study the investigators will include both autoimmune and non-autoimmune urticaria, since the efficacy could differ between both urticaria types. In the same way, the Health Authorities (AEMPS) would have independent additional information obtained through adequate methodology in the case that a new indication is requested. The investigators also want to stress that in the near future the company that manufactures this antibody could ask for a new indication for chronic urticaria.