Cetirizine, sold under the brand name Zyrtec, is an antihistamine medication used to relieve allergy symptoms such as runny nose, sneezing, itchy eyes/nose, hives, and itching. It works by blocking histamine, a substance released by the body during an allergic reaction. Zyrtec can be used for temporarily relief of common allergy symptoms such as runny nose, sneezing, itchy, watery eyes, and itching of the nose or throat. It is available in multiple forms, including tablets, capsules, gels, dissolve tablets, and liquid. For adults and children 6 years and older, the recommended dosage is one 10 mg tablet once daily, and a 5 mg product may be appropriate for less severe symptoms. It is important to read and follow the label, including the directions, before taking this over-the-counter allergy medication. If you have questions, consult your doctor or pharmacist.