The active ingredient in Allegra 120 is Fexofenadine Hydrochloride, a second-generation antihistamine known for its ability to block histamine H1 receptors without crossing the blood-brain barrier, which significantly reduces the risk of sedation and drowsiness—a common issue with older antihistamines. Allegra 120 works by preventing the effects of histamine, a chemical naturally produced by the immune system in response to allergens. When histamine is released, it causes inflammation, swelling, itching, sneezing, a runny nose, and watery eyes.
