The appearance of a red rash on the body after the MMR vaccination is considered to be probably due to an adverse reaction to the vaccine. The red rash after MMR vaccination is mainly caused by the reaction of some components in the vaccine. Due to the different constitution of individuals, some children may have a red rash on the surface of the body after vaccination, and sometimes it may be accompanied by fever, some heavy and some light, which is mainly caused by the adverse reaction, and it’s a common phenomenon, and it doesn’t need special treatment in general. When the adverse reaction occurs, it is recommended to drink more warm water, eat more fresh fruits and vegetables, keep the local skin clean, change clothes diligently, etc., after a few days, the red rash will basically subside on its own. If the rash has not been relieved, you should go to the hospital in time to find out the cause of the disease and treat the symptoms.