The fact that the fever is reduced and the fever is raised again proves that the disease in the body is not under control, and the antipyretic medicine can only play the role of symptomatic treatment and can only be maintained for a certain period of time after the fever is reduced, after which the body temperature is still elevated proves that there is an infection or other conditions in the body that are not under control, and the cause of the fever needs to be specifically identified. Infectious fever is often divided into infectious fever and non-infectious fever, common acute fever is often infectious fever, infectious fever in addition to increased body temperature is accompanied by clinical symptoms of the corresponding parts, such as lung infection patients accompanied by cough, coughing sputum, chest pain, dyspnea and other symptoms, it is recommended to do lung CT or chest X-ray examination to clarify the diagnosis; patients with right upper abdominal pain accompanied by nausea, vomiting, mouth bitterness, skin yellowing, etc. The symptoms may be biliary system infection, and ultrasound examination of liver, gallbladder and spleen is recommended. The fever may also be non-infectious fever including rheumatic immune system diseases, tumors, etc. After the fever has subsided, the cause of the fever should be specifically analyzed and treated from the etiology in order to restore the body temperature to normal.