Zyrtec Cetirizine HCl tablets 10 mg / antihistamine for indoor and outdoor allergies. 24 hours relief of sneezing, runny nose, itchy, watery eyes, itchy throat or nose. Directions: adults and children 6 years and over - one 10 mg tablet once daily; do not take more than one 10 mg tablet in 24 hour. A 5 mg product may be appropriate for less severe symptoms.