The antihistamines with inhaled steroids are the cornerstone on the symptomatic therapy in the management of patients with rhinitis and the first line of treatment in patients with urticaria. Currently, the use of antihistamines has become popular due to its excellent safety profile and clinical efficacy, however to the investigators knowledge, there are no studies about the pharmacokinetic and pharmacodynamic effects of these drugs in patients of tropical Latin America. The investigators main interest is to evaluate if skin test inhibition correlates with the clinical effect of five anti-histamines.

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.

Inclusion Criteria:

• Clinical diagnosis of persistent allergic urticaria.
• Age over 12 years and at least one year with the disease
• Informed consent filled.
• Be resident of the metropolitan area of Medellin.

Exclusion Criteria:

• • Use of immunosuppressive drugs