Usually a simple fever of 40°C has no adverse effect on the brain and does not cause any damage to the body. However, if the patient is accompanied by intracranial infection and high fever convulsions, brain cells can be damaged and need to be given aggressive symptomatic treatment. The basic components of brain cells are proteins, which are gradually destroyed only at 42°C or higher. If it is only a simple fever with a temperature up to 40℃, it usually does not cause damage to the brain; if the fever is caused by encephalitis or meningitis, it can affect the normal metabolism and function of brain cells and may induce symptoms such as convulsions and hyperthermia, resulting in functional damage to brain cells, which often has a greater impact on the patient. Therefore, when the patient’s body temperature is as high as 40°C, active symptomatic treatment is required, with oral administration of ibuprofen and other drugs to control the body temperature, drinking more water, and physical cooling. If the patient’s temperature remains high, symptomatic treatment should be given at a fever clinic or internal medicine department without delay.