Cetirizine is a second generation antihistamine which is primarily used in the treatment of conditions such as urticaria, hayfever, allergies and angiodema.

Being a second generation antihistamine, cetirizine crosses the blood brain barrier only slightly, which in turn reduces the sedative side effect associated with older types of antihistamines. Second generation antihistamines also have less of a tendency to induce drowsiness or interfere with memory formation, as some first generation drugs can. Cetirizine works by blocking the H1 receptor, temporarily alleviating the itchiness and redness caused by histamine acting on this receptor.

Some common side effects of cetirizine include headache, dry mouth and fatigue.