Antihistamines are currently only available in three generations, not four. Third-generation antihistamines include desloratadine tablets, levocetirizine hydrochloride tablets, etc. They are recommended to be used under doctor’s supervision. Third-generation anti-allergy drugs include desloratadine tablets, levocetirizine hydrochloride tablets and so on. The main features of third-generation anti-allergy drugs are less side effects, higher safety and more rapid anti-allergy effect. They can be used in the treatment of chronic idiopathic urticaria, allergic rhinitis and other diseases. Drugs need to be used under the guidance of a doctor, to avoid self-medication.