If your baby has a red rash after a fever, first of all, you have to understand whether it is when the fever is on or after the fever has subsided. If the rash comes on when the fever is on, it can be seen as rubella, measles, chicken pox, etc. If the rash comes on after the fever has subsided, it is considered to be an infant emergency rash. It is advisable to check the blood routine first to understand the specific infection, as well as to observe the pattern of fever and the characteristics of the rash, which is generally caused by viral infections and can also be seen in bacterial infections. The rash that comes out after the fever subsides is considered to be an early childhood emergency rash, also known as early childhood rose rash, which is a common acute rash disease in infancy and early childhood. It is transmitted through the respiratory tract and can develop throughout the year, with winter and spring being the two most common seasons, with the age of onset being 6 months to 2 years. The main clinical features are sudden onset of high fever and fever withdrawal rash. The fever usually lasts 3 to 4 days, the body temperature drops to normal, and a rash appears all over the body when the fever subsides or a few hours to 1 to 2 days after the fever subsides. The rash first appears on the neck and chest and soon spreads to the whole body. Due to the lack of specificity in the symptoms and signs of the disease, it is difficult to make a diagnosis in the early stages until the rash appears all over the body after the fever subsides. If the rash is an early childhood emergency, no special treatment is needed, and the rash can all recede within 1 to 2 days, leaving no discoloration and no flaking. The prognosis for this disease is good, and lifelong immunity can be obtained after getting the disease, which generally does not recur. If it is measles, chickenpox, etc., which is strongly contagious, it is necessary to do a good job of isolation and not to go out to prevent infection. To treat the symptoms and the cause, you can take some oral anti-viral drugs and oral antipyretic drugs for fever over 38.5℃. It is important to observe the child’s mental state, facial color, breathing, and the presence of limb tremors. In serious cases, it is important to prevent complications, such as viral encephalitis and viral myocarditis.