We are now in the early fall season, although it is no longer hot and even a little cooler, and at the same time it is the season of harvest, which should be the best. But the discordant thing is that this change of seasons also happens to be the high incidence of allergic rhinitis, urticaria and other allergic diseases. The symptoms caused by allergies such as chest tightness, difficulty in breathing, conjunctival congestion, rashes and nausea can be a bit daunting. What should I do if I have an allergy? For allergies, the first two anti-allergy drugs that should come to our mind are loratadine and levocetirizine hydrochloride, which are two of the more effective anti-allergy drugs. However, there are differences in their use, and in different cases, different anti-allergy drugs are needed. Today we will talk about the differences between them: a. Indications are slightly different, levocetirizine hydrochloride is available in tablets and granules, and is a selective histamine H1 receptor antagonist. It is mainly used to relieve allergic symptoms of allergic diseases, clinically used for the treatment of allergic rhinitis, urticaria, angioneurotic edema and other allergic diseases of the skin and mucous membranes; also used to relieve the allergic symptoms of colds. And loratadine, a second-generation antihistamine, is commonly used to treat allergic symptoms. Compared with the first generation antihistamines, one of its major properties is its non-drowsy effect. It is used for allergic rhinitis, acute or chronic urticaria, allergic conjunctivitis, hay fever and other allergic skin diseases. Second, the dosage should be based on age. 12-year-old children and adults use cetirizine and loratadine are long-acting preparations, easy to take, 10 mg once a day. 2 years to 12 years old children weighing ≥ 30 kg, according to the adult dose; weight ≤ 30 kg, the dose needs to be reduced by half. 1 to 2 years old children can use cetirizine hydrochloride drops, strict control of the dose, if there are adverse reactions Children under 2 years of age are not allowed to use loratadine, there are clear drug interactions and cardiotoxic side effects. children under 1 year of age currently have clinical data from studies proving that the minimum age of children using cetirizine is 6 months. Third, beware of adverse reactions such as drowsiness. Clinical applications have shown that no significant sedative effects were seen when loratadine was taken at the recommended dose (10 mg). Adverse reactions such as drowsiness, dry mouth, headache, malaise, gastrointestinal discomfort, and rare tachycardia and palpitations were common. Cetirizine causes drowsiness, weakness and other adverse reactions are short-lived and transient. If patients who are engaged in driving or working at height need to take these drugs, they can change the time of taking them to night. Although the anti-allergic effect of these two drugs is good, but in the use of medical advice, according to different age and physical condition and the nature of work, choose to take different drugs and dosage, and also the time of taking the drug is also need to pay attention to some.