(R)-Cetirizine, also known as levocetirizine, is the active enantiomer of cetirizine used to treat allergy symptoms such as sneezing, runny nose, itching, and watery eyes. It is particularly effective for seasonal or perennial allergies and in managing chronic urticaria (hives) and other skin allergies by reducing itching and redness.

As a selective H1 receptor antagonist antihistamine, it acts peripherally with minimal crossing into the central nervous system, resulting in less drowsiness compared to older antihistamines or the racemic cetirizine.

Due to its higher bioavailability and potency, (R)-cetirizine is administered at lower doses than the parent compound (e.g., cetirizine hydrochloride) while providing equivalent or superior symptom relief, thereby reducing the risk of side effects and enhancing safety for long-term use.

Commonly available in oral formulations such as tablets or syrup for once-daily dosing, it offers convenient, long-lasting relief and is suitable for both adults and children without significantly disrupting daily activities.