Children with a fever of 40 ℃ is certainly dangerous, this is already a high fever, generally 38.5 ℃ below the body temperature is considered a low fever, the problem is not too big, but the high fever will cause a lot of harm, including convulsions, convulsions, for the brain can also cause some damage, so you should go to the hospital in a timely manner, to take medication to reduce the fever or according to the appropriate condition to receive infusion therapy, but also drink more water, pay attention to rest. Children with a fever of 40 ℃ should find the cause of the fever, to see what the cause is, whether it is a bacterial infection or a viral infection. If it is a bacterial infection, it depends on which part of the body is infected, such as pneumonia, urinary tract infection or other parts of the body. If it is a viral infection, it depends on whether it is caused by common virus, cold virus, or influenza virus, so we should go to the hospital in time for different situations, and do not take medicines on your own, so as not to delay the condition.