Medscape - Seasonal allergic rhinitis, chronic idiopathic urticaria-specific dosing for Allegra (fexofenadine), frequency-based adverse effects, comprehensive interactions, contraindications. 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. While some other oral antihistamines may cause you to be drowsy, Allegra® won't. 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. Allegra is a non-drowsy antihistamine for allergy relief. Here’s our guide for dosing Allegra for kids and adults, and what to do if you miss a dose or take too much. 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. Fexofenadine (Allegra) is an antihistamine that treats and prevents allergy symptoms. It blocks histamine to reduce your symptoms. Get fast-acting relief from seasonal allergies and symptoms like a runny nose, sneezing, itchy, watery eyes, and itchy nose or throat. Allegra ® kicks in within just one hour with 0% brain interference from drowsiness—that's right, it doesn't enter your brain and leave you feeling groggy. 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. Detailed dosage guidelines and administration information for Allegra (fexofenadine hydrochloride). Includes dose adjustments, warnings and precautions. It is a common over-the-counter medication available under many brand names (including Allegra), as well as a generic drug. [11] Therapeutically, fexofenadine is a selective peripheral H 1 blocker.