Hydroxyzine hydrochloride is a sedating antihistamine used mainly to treat anxiety disorder and tension and, in combination with some other medications, to treat anxiety resulting from physical illness. As an antihistamine, it works by preventing the effects of histamine, substances produced by the body that cause itching, sneezing, runny nose, and watery eyes, and other allergic symptoms. It also relieves itching from allergic reactions and has a sedative effect before and after general anesthesia. It is also used to treat motion sickness by reducing nausea. Hydroxyzine hydrochloride has several trade names with Atarax and Vistaril are among the most popular.