 This was a randomized, double-blind, study that was conducted in six health care centers from Medellín and Bogotá Colombia. This study was conducted in compliance with the ethical principles of the Declaration of Helsinki and with Good Clinical Practice guidelines. Written informed consent was obtained from all subjects or they parents in patients under 18 years. Ethical committee of University of Antioquia Medellín, Colombia approved the protocol. Considering the large number of articles that demonstrate the efficacy of antihistamines as first-line treatment in patients with urticaria, the ethics committee request that all participants would receive an antihistamine during the two months of the study because a placebo group would provide little information for the principal objective and the high risk of airway angioedema. Thirty heath subjects were used as a control group to evaluated the characteristics of the wheal in the prick test with histamine. 