After MMR vaccination, if the rash is localized and mild, usually no treatment is needed. If the rash is more serious or there are other more serious accompanying symptoms, then timely medical treatment is needed. If the rash after MMR vaccination is localized and mild, it is considered to be a general adverse reaction caused by vaccination, which is a normal phenomenon and usually requires no treatment and can subside on its own. However, if the rash is large and increasing, it is considered to be a more serious allergic reaction and requires prompt medical attention. Since there are different types of rashes caused by vaccinations, it is necessary to go to the hospital to get a clear picture of the condition and then follow the doctor’s instructions for appropriate treatment.