Continuous fever can be harmful to the body, most often to the brain. However, each person has a different body type and a different degree of tolerance to fever, so there is no way to specify how long it affects the brain. When a person’s body temperature is greater than 42°C, the nervous system is in a state of excitement and the proteins, which are the basic building blocks of brain tissue, are gradually destroyed. In pediatric patients, the neurological system of small children is not well developed, which may lead to transient neurological disorders for a short period of time, and continued development may cause cerebral edema, resulting in serious irreversible damage, as well as dysfunction of cerebral cortical excitation and inhibition, loss of body fluids, reduced secretion of digestive juices, reduced digestive enzyme activity, gastrointestinal disorders, and a series of serious symptoms. In addition, persistent high fever is usually due to the presence of certain inflammatory diseases, viral infections or malignant tumors in the organism, which should be promptly visited to the hospital to identify the cause and provide reasonable treatment for the cause to reduce the damage to the organism. There is no specific definite time when a fever will affect the brain, it varies from person to person. When a person’s body temperature exceeds 38.5℃, it is necessary to take antipyretic drugs in time, and if the effect is not good enough to go to the hospital to avoid serious consequences.