Generic Name: fexofenadine (FEX oh FEN a deen) Brand Names: Allegra, Allegra ODT What is Allegra? Allegra is an antihistamine that reduces the natural chemical histamine in the body. Histamine can produce symptoms of sneezing, itching, watery eyes, and runny nose. Allegra is used to treat the symptoms of seasonal allergies (hay fever) in adults and children. Allegra is also used to treat skin itching and hives caused by a condition called chronic idiopathic urticaria in adults and children. Please consult your physician before taking this medication.