Cetirizine hydrochloride, or cetirizine hcl, is an antihistamine used to treat symptoms associated with allergies and the common cold, such as sneezing, runny nose, itching and watery eyes, according to Drugs.com. The most common brand name for cetirizine is Zyrtec, which can be purchased over the counter at drug stores.
Histamine is a naturally present chemical in the human body. When the body encounters an allergen, it produces a higher than normal amount of histamine; antihistamines work to neutralize those histamines, thereby preventing an immune response that results in the symptoms associated with an allergic reaction or cold virus, as explained by TreatAllergies.com.
There are side effects associated with this medication, the most common of which is drowsiness. It is important to speak with a medical provider before taking this medication, notes Drugs.com, especially when already taking medications that cause tiredness.