Zirtek Allergy Tablets Zirtek Allergy Tablets relieve the symptoms of hayfever & year round allergies such as dust or pet allergies & urticaria. They contain the antihistamine cetirizine hydrochloride, which blocks the histamine response involved in allergic reactions to relieve the unpleasant symptoms & discomfort associated with these conditions, such as sneezing, irritated, runny & blocked up nose, itchy, red & watering eyes & skin rashes.