Levocetirizine hydrochloride tablets are clinical anti-allergy drugs, which are histamine H1 receptor blockers and are mainly indicated for the treatment of allergic rhinitis, urticaria and other allergic diseases. 1 tablet is usually taken once daily, and patients are advised to take it at night before going to bed. Although levocetirizine hydrochloride rarely has the side effect of drowsiness, for a very small number of patients, especially those with high blood-brain barrier permeability, levocetirizine hydrochloride may enter the central nervous system and cause symptoms such as drowsiness. Therefore, it needs to be used with caution for drivers or patients working at height. Also, levocetirizine hydrochloride should not be used simultaneously with macrolide antibiotics and antifungal drugs to avoid damage to liver function.