Allegra

Fexofenadine is an antihistamine pharmaceutical drug used to treat allergy symptoms such as hay fever and urticaria. It is a selective peripheral H1 blocker and is classified as a second-generation antihistamine, meaning it is less likely to cause sedation. Fexofenadine is used to relieve symptoms of seasonal allergic rhinitis and to treat hives, including chronic urticaria, and has been shown to be safe for individuals with inherited long QT syndrome. The most common side effects of fexofenadine include headache, back and muscle pain, miosis, nausea, drowsiness, and menstrual cramps, with no significant adverse effects reported in overdose cases. Fexofenadine is a selective peripheral H1 receptor antagonist that blocks the activation of H1 receptors by histamine, preventing allergic symptoms, and it does not readily cross the blood-brain barrier, making it less likely to cause drowsiness.learn more on wikipedia