Fever is a common clinical symptom that generally refers to an increase in body temperature above normal levels. There are many causes of fever and therefore a variety of accompanying symptoms, and a red rash on the body with fever is one of them. The first thing you should consider is the possibility of drug allergies. When you have a fever, you often need to take some antipyretic and cold medicine, and due to the different constitutions of individuals, you may have allergic symptoms to the above drugs, and you may get a red rash on your body. If the rash is caused by drug allergy, you should immediately stop using the drug, usually the rash will automatically subside within a short time after stopping the drug, if it does not subside within 3-5 days, you should promptly go to the hospital for medical attention. Secondly, fever caused by viral infection may also appear red rash, there is no need to worry too much at this time, the rash will be automatically eliminated within one to two days after the recovery of the cold and fever. When you have a fever with a red rash, you should keep your body clean and hygienic, pay attention to a light diet, and eat more vegetables and fruits. If necessary, you can take oral anti-viral oral solution, or take some drugs to clear the heat and detoxify the body. There are also some infectious diseases often manifested as fever, rash, especially in young children with a cold and fever red rash on the body, may be infectious diseases, such as chicken pox, rubella, early childhood emergency rash, etc., this time must be taken seriously, to the hospital in a timely manner, and at the same time pay attention to take appropriate isolation measures. In short, the red rash that appears on your body when you have a fever can be mild or severe. Especially in pediatrics, if there is a history of contact with patients with infectious diseases, it must be treated with caution and the cause should be identified and treated.