We offer Cetirizine Syrup.. Cetirizine hydrochloride, an antihistamine, is a major metabolite of hydroxyzine, and a racemic selective H1 receptor inverse agonist used in the treatment of allergies, hay fever, angioedema, and urticaria. Cetirizine is a highly potent long-acting peripheral H1-receptor antagonist which acts both on the early and late allergic response.