How to use Zyrtec. If you are taking the over-the-counter product to self-treat, read all directions on the product package before taking this medication. One 10 mg tablet once daily; do not take more than one 10 mg tablet in 24 hours. A 5 mg product may be appropriate for less severe symptoms. A 5 mg product may be appropriate for less severe symptoms. Zyrtec (cetirizine) is an antihistamine that reduces the effects of natural chemical histamine in the body. Histamine can produce symptoms of sneezing, itching, watery eyes, and runny nose. Cetirizine, sold under the brand name Zyrtec among others, is a second generation antihistamine used to treat hay fever, dermatitis, and urticaria. It is taken by mouth. Available in 4 fl oz. (118 mL) Children’s ZYRTEC® Allergy Syrup, Dye-Free, Sugar-Free Grape also available in 2-pack of 4 fl. oz *Provides relief of sneezing, runny nose, itchy, watery eyes and itchy nose and throat. Zyrtec Images. What does Zyrtec look like? Note: Multiple pictures are displayed for those medicines available in different strengths, marketed under different brand names and for medicines manufactured by different pharmaceutical companies. Find patient medical information for Cetirizine Oral on WebMD including its uses, side effects and safety, interactions, pictures, warnings and user ratings. Zyrtec is an antihistamine used to treat seasonal allergies and hives. It is available over the counter, though children under six with hives will still need a prescription. Consumer information about the medication CETIRIZINE - ORAL (Zyrtec), includes side effects, drug interactions, recommended dosages, and storage information. Read more about the prescription drug CETIRIZINE - ORAL. See images of Cetirizine (Generic Zyrtec), including the medication and its packaging.