Compare to the active ingredient in Zyrtec tablets. One dose of Cetirizine Hydrochloride 10 mg tablets, works for a full 24 hours to relieve allergy symptoms. Cetirizine Hydrochloride Tablets are an antihistamine approved for the treatment of both indoor and outdoor allergy symptoms in adults and children 12 years of age and older. 24-hour temporary relief of these symptoms due to hay fever or other upper respiratory allergies: runny nose; sneezing; itchy, watery eyes; itching of the nose or throat.