Medically reviewed by Lindsay Cook, PharmD Xyzal (levocetirizine) and Zyrtec (cetirizine) are antihistamines taken to relieve allergy symptoms such as sneezing, runny nose, itchy eyes, and hives.

Diarrhea and coughing have also been observed in children. Cetirizine, the active ingredient of Zyrtec, is a second-generation antihistamine that blocks the action of histamine (a product of the ...