Rashes on the body with fever are common in pediatrics for some infectious diseases, such as measles, early childhood emergency rash, rubella, and scarlet fever, and the fever is not consistent with the rash for each disease. There are also blood disorders that can manifest themselves as fever, such as acute leukemia. Patients with measles present with cough, runny nose, and tearfulness in addition to fever, and often present with a rash after 3 to 4 days of fever. Early childhood emergency rash is mainly caused by human herpes virus types 6 and 7 infection. After 3 to 5 days of fever, the body temperature returns to normal and the rash subsides, and some rose-colored maculopapular rash may appear at this time; rubella mainly appears after 1 day of fever; and scarlet fever mainly appears within a few hours to a day of fever, and the body temperature rises when the rash appears. In addition, a red rash after a fever can also be an allergic reaction, such as a drug allergy to fever-reducing medication or antibacterial agents. The fever can be an early manifestation of acute leukemia, and the patient will also appear petechiae or petechiae on the skin; patients with idiopathic thrombocytopenic purpura often have an acute onset, and after the patient develops high fever, petechiae and petechiae on the skin all over the body, and even hematoma and hematoma formation; for these cases of fever and rash, you should avoid blindly applying antipyretic drugs, and promptly seek medical attention to find out the cause of the disease and treat the cause. Treatment, at the same time, some dermatological ointment can be used to wipe the rash to relieve localized skin swelling and pain, itching, etc.