Levocetirizine is a second-generation antihistamine that works by preventing the effects of a substance called histamine, which is produced by the body. Histamine can cause itching, sneezing, runny nose, and watery eyes. Levocetirizine is used for the treatment of allergic rhinitis (hay fever) and long-term hives of unclear cause. It is less sedating than older antihistamines.