The active component in Zyrtec 10 tablets is cetirizine. This anti-allergic medication is used to treat the symptoms of a variety of allergic disorders, which include hives, fever, rash, sinusitis, runny or blocked nose, watery eyes, and fever. You should take Zyrtec 10 tablets exactly as directed by your physician. Avoid stopping this medication earlier than advised as this could lead to treatment failure. This medication should not be administered to patients with severe kidney problems or to children under the age of six.