A fever of 40.5 degrees Celsius, if it remains untreated, may produce irreversible damage and serious sequelae, which is a very dangerous situation. 40.5 degrees belongs to the high fever range. Prolonged exposure to high fever can easily lead to hyperthermic convulsions, generalized weakness, aches and pains, disturbances in water-electrolyte balance, and induced heart failure, among other symptoms. In addition to this, high fever can also damage proteins in the body, causing brain cell degeneration. Therefore, it is necessary to immediately lower the temperature treatment, can use drugs to assist cooling, such as ibuprofen, etc.; at the same time, combined with physical cooling, such as the use of alcohol wipe or ice packs and other methods to dissipate the heat; but the main thing is to treat the original disease. It is recommended to send to the hospital for treatment as soon as possible.