Cetirizine, which is sold under the trade name, Zyrtec, is a non-sedating second generation antihistamine. An antihistamine prevents sneezing, wheezing, itching of the nasal passages, and itching of the eyes caused by allergic symptoms. The medication blocks the effects of histamines that cause allergic reactions. It is primarily prescribed to treat allergic rhinitis caused by indoor and seasonal allergies to substances such as dust mites, mold spores, tree, grass, and weed pollen, as well as animal dander. It is also used to treat skin allergies like hives (urticaria), angioedema, and hay fever as well as other inflammatory conditions. It is commonly prescribed in combinations with pseudoephedrine hydrochloride, a decongestant.