Fexofenadine is an antihistamine pharmaceutical drug used in the treatment of hay fever, allergy symptoms, and urticaria.It was developed as a successor of and alternative to terfenadine, an antihistamine that caused QT interval prolongation, potentially leading to cardiac arrhythmia. Fexofenadine, like other second- and third-generation antihistamines, does not readily cross the blood–brain barrier, and so causes less drowsiness than first-generation histamine-receptor antagonists. It works by being an antagonist to the H1 receptor. Fexofenadine is indicated for relief from physical symptoms associated with seasonal allergic rhinitis and for treatment of chronic urticaria. It is not a therapeutic drug and does not cure but rather prevents the aggravation of rhinitis and urticaria and reduces the severity of the symptoms associated with those conditions, providing relief from repeated sneezing, runny nose, itchy eyes and general body fatigue.