Overview: Fexofenadine is an antihistamine that is taken to help treat allergy symptoms, such as a runny nose, itchy or watery eyes, sneezing, or an itchy nose or throat. Common side effects may. In general, Zyrtec, Claritin, and Allegra all work similarly well for treating allergies. But some studies suggest Allegra might work slightly better for eye-related symptoms. Allegra (fexofenadine) is a non-drowsy antihistamine used for seasonal allergic rhinitis and chronic idiopathic urticaria. Compared with first-generation agents, it has minimal CNS penetration and is less sedating, making it suitable for daytime use and tasks that require alertness. What is Allegra? Allegra (fexofenadine) is an antihistamine used to treat allergy symptoms, including sneezing, itching, watery eyes, and a runny nose in adults and children. Fexofenadine (Allegra) is an antihistamine that treats and prevents allergy symptoms. It blocks histamine to reduce your symptoms. Antihistamines work by preventing the effects of a substance called histamine, which is produced by the body. Histamine can cause itching, sneezing, runny nose, and watery eyes. Also, in some people histamine can close up the bronchial tubes (air passages of the lungs) and make breathing difficult. Shop Allegra Adult 24 Hour Allergy Tablets, Non-Drowsy Antihistamine and read reviews at Walgreens. Pickup & Same Day Delivery available on most store items. Fexofenadine, the active ingredient in Allegra ®, provides non-drowsy allergy relief with 0% brain interference, relieving allergy symptoms like sneezing, runny nose and itchy eyes. Fexofenadine, sold under the brand name Allegra among others, [10] is an antihistamine medication used in the treatment of allergy symptoms such as allergic rhinitis and urticaria. Allegra allergy relief medicine starts working in one hour for relief from sneezing, runny nose, itchy and watery eyes, and itchy nose or throat. One pill provides 24-hour allergy relief that doesn’t make you drowsy and affect your normal brain function.