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 (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. 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. Detailed dosage guidelines and administration information for Allegra (fexofenadine hydrochloride). Includes dose adjustments, warnings and precautions. Want fast, non-drowsy allergy relief? Allegra helps relieve your toughest allergy symptoms, without the drowsy effect, empowering you to live life fully*, everyday. 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. Medscape - Seasonal allergic rhinitis, chronic idiopathic urticaria-specific dosing for Allegra (fexofenadine), frequency-based adverse effects, comprehensive interactions, contraindications. Allegra (Fexofenadine Hcl) may treat allergy, side effects, dosage, drug interactions, warnings, patient labeling, reviews, and related medications including drug comparison. 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.