After the MMR vaccine, if the rash is mild, it usually does not need special treatment. If the symptoms are more serious, it may be caused by allergy and can be treated with drugs such as dexamethasone. MMR vaccine can be used to prevent measles, mumps and rubella, and is suitable for infants and children over 8 months of age. After receiving the vaccine, there may be swollen lymph nodes in the neck or mild fever or rash, which are common side effects of the vaccine and are not contagious, and can be relieved on their own after a period of time, and usually do not require special treatment. However, if the rash is more serious, it may also be caused by allergy, and can be injected with dexamethasone for anti-inflammatory and anti-allergy treatment by a professional doctor, and can also be taken orally with anti-allergy medications such as cetirizine drops, loratadine syrup, and so on. Parents are advised to consult a doctor for standardized treatment.