A fever of 40℃ is a super high fever, which is very dangerous and can be life-threatening. A fever of 40℃ will cause more damage to the body organs, resulting in a faster heart rate and increased evaporation of water from the body, which can lead to pneumonia and encephalitis, and the possibility of bacterial meningitis or sepsis is higher. The limit of high temperature that brain cells can tolerate is 41.7°C. If this temperature is exceeded, the cells will deteriorate due to high temperature and cause irreversible damage. Patients often show neurological symptoms, such as irritability and drowsiness, or manifestations such as neck tonicity, headache, and violent vomiting, which are generally more dangerous and even life-threatening. Therefore, when the body temperature reaches this level, active antipyretic treatment is required, and symptomatic treatment such as intravenous fluids, water-electrolyte supplementation, and oral antipyretic drugs are recommended, as well as active etiological examination to determine the etiological typology for targeted treatment.