Clinically there is no special effect method to reduce fever quickly with a high fever of 40 degrees Celsius, which can be achieved through physical cooling and the combined use of drugs to achieve the purpose of lowering the temperature. 40 degrees belongs to high fever, usually seen in bacteria, viruses, mycoplasma and other pathogenic infections. The first thing to do is to lower the body temperature to avoid convulsions. You can take oral ibuprofen granules or acetaminophen suspension to relieve fever and analgesia, and at the same time, use warm water to wipe or cold compresses to increase the body surface heat dissipation, to speed up the cooling. Fever-reducing medicines should not be mixed or used alternately. If a fever-reducing medicine is not effective after 2 hours of taking it, take other fever-reducing medicines after an interval of 2 hours. In the face of a high fever of 40 degrees, it is recommended to consult a doctor as soon as possible, and actively search for the cause. After the diagnosis is clear, follow the doctor’s instructions to standardize the treatment. The use of drugs must follow the doctor’s advice, not blindly use their own medicine, so as not to cause adverse consequences.