Cetirizine is an antihistamine available in over-the-counter (OTC) medicines that treat symptoms due to hay fever or other outdoor and indoor allergies. It may be written as cetirizine or cetirizine hydrochloride (HCl), but it is the same active ingredient. Cetirizine can be the only active ingredient in an allergy medicine, or it can be found in medicines that relieve other symptoms, such as nasal congestion.
Cetirizine is approved by the U.S. Food and Drug Administration (FDA) and is safe and effective when used according to label directions. But keep in mind that not all medicines are right for all people. For example, cetirizine can pass into breast milk, so it is not recommended for women who are nursing.