Histamine H1 receptor (H1 or HRH1) is a subclass of histamine receptors. It mediates the contraction of smooth muscles, increase in capillary permeability due to contraction of terminal venules, and catecholamine release from adrenal medulla, and neurotransmission in the central nervous system. Antihistamines including H1 receptor antagonists are among the most frequently used pharmacologic agents because of a high incident rate of upper respiratory allergies. Clinical and laboratory evidence on histamine and its actions suggests that it has a pathophysiologic role in asthma. These findings have renewed interest in the potential therapeutic role of H1-receptor antagonists, such as, fexofenadine, which has been investigated as potential therapeutic targets for this disease.