The baby’s fever of 40 degrees is already high, burning overnight is likely to burn the brain, you need to timely physical cooling, and take the child to the hospital for diagnosis and treatment, under the guidance of the doctor to take antipyretic drugs to prevent complications caused by high fever. The baby’s nervous system is not well developed and is sensitive to high fever. 40 degrees is already a high fever state, if not controlled, there will be febrile convulsions, which can cause lack of oxygen to the brain, resulting in brain damage and even epilepsy and cerebral palsy in severe cases, so the first thing to do is to reduce the heat. Temporary physical cooling can be done, for example, you can use warm water baths, or you can use ice pillows or wear ice caps, which can reduce the temperature of the brain and ensure that the central nervous system is not damaged. You can also take antipyretic drugs, such as ibuprofen suspension, and you can also use antipyretic suppositories. At the same time, parents need to take their children to the hospital in a timely manner for emergency blood tests, C-reactive protein, chest x-ray, etc., to clarify the cause of the high fever and then give corresponding treatment. During the period of fever reduction treatment, parents should actively replenish fluids to prevent dehydration and metabolic disorders, drink more water, and keep the child warm to avoid catching another cold.