Zyrtec® contains cetirizine hydrochloride, a selective H1-receptor antagonist that helps block the action of histamine, one of the primary substances responsible for allergic reactions. By reducing histamine activity, cetirizine helps relieve symptoms such as sneezing, nasal congestion, itching, watery eyes, and skin irritation.

The medication is widely used for the treatment of seasonal and perennial allergic rhinitis, chronic urticaria (hives), allergic conjunctivitis, and other allergy-related conditions. Its long-lasting action provides effective symptom relief for up to 24 hours with once-daily dosing in many patients.

As a second-generation antihistamine, cetirizine is generally associated with a lower incidence of sedation compared to first-generation antihistamines, making it suitable for daily allergy management in many individuals.

Treatment decisions, dosing schedules, and duration of therapy should always be determined by a qualified healthcare professional.