Children’s antihistamines are a class of drugs that act as histamine antagonists by binding to histamine receptors, and are mainly used to treat allergic diseases such as urticaria, atopic dermatitis, eczema, and asthma. Antihistamines are clinically divided into three categories, including first-generation antihistamines, second-generation antihistamines and third-generation antihistamines.1. First-generation antihistamines: common in chlorpheniramine maleate, diphenhydramine hydrochloride, cyproheptadine hydrochloride, etc., are easier to cross the blood-brain barrier and may produce central inhibition, so they are also called sedative antihistamines. It can cause adverse reactions such as drowsiness, fatigue and inattention in children. Long-term application may also affect the cognitive function of infants and children, as well as the learning situation of school-age children, so long-term application is not recommended; 2. Second-generation antihistamines: commonly used in loratadine, cetirizine hydrochloride, etc. The chemical structure characteristics are basically similar to the first generation, mainly improving the adverse reactions. Therefore, with the same therapeutic dose, there are no or less central side effects, but there may be occasional cardiac side effects, such as possible panic and palpitations in children; 3. Third-generation antihistamines: common in fexofenadine hydrochloride, levocetirizine hydrochloride, etc., which are safer than second-generation drugs and have more clinical applications, and are also relatively safer drugs. For children who need to learn, they should try to choose third-generation antihistamines. Since the immune function of children is not yet perfect, they are more prone to allergic situations. After an allergic reaction, symptoms such as itching, blistering and sneezing usually occur. It is recommended to clarify the allergen and stay away from it while treating. If the symptoms of allergy in children are more serious, they can be treated with antihistamines as prescribed by the doctor.