Fever is usually caused by bacteria, viruses or their metabolites. After fever, the heart rate increases, blood circulation is accelerated, and the amount of blood flowing to the inflamed area increases, which on the one hand can dilute and take away bacteria and the toxins produced, and on the other hand, the number of white blood cells increases, which can directly destroy and devour bacteria and viruses, but also produce an endogenous thermogenic substance to stimulate the production of antibodies that have the ability to kill bacteria or viruses and promote the improvement of the condition. It also temporarily stores iron in the blood in the liver, making it difficult for bacteria to grow as soon as they lack iron. If antipyretic drugs are used just after the onset of fever, not only is it difficult to achieve the above series of changes, but it can also mask the condition. It is generally advocated to use cooling treatment in the following cases: 1. fever in in above 38.5 ℃ ℃; 2. fever discomfort and affect the rest of the child; 3. fever with irritability or agitation, jumping and other convulsive aura; 4. a history of high fever convulsions. Cooling generally use physical cooling (such as cold water soaked towel on the forehead, groin, axilla and other large blood vessels), or head resting on an ice pack, or 50% alcohol rubbing limbs, neck, large blood vessels to the skin red) and drug cooling (such as aspirin, antipyretic suppositories, Advil, etc.). Do not use too much medicine to reduce fever, and pay attention to the child’s mental condition, and let the child drink more water to facilitate sweating to lower the temperature. Once the child’s spirit is not good or the temperature does not drop after medication, you should see a doctor without delay!