Rash after MMR vaccination may belong to normal reaction or allergic reaction, which can be treated without any treatment or by using medication. 1. Normal reaction: If the scope of the rash is very small, the number is very small, and the symptoms are not very serious, this is a normal reaction after vaccination, and it will subside by itself in 2-3 days after MMR vaccination, and this situation can be treated without any treatment. 2. Allergic reaction: after MMR vaccination, if there is a large, widespread rash, etc., accompanied by itching and other symptoms, it is necessary to consult the doctor in time, and it can be considered to be caused by drug allergy, which can be treated by using anti-allergic drugs such as loratadine granules and cetirizine hydrochloride drops. If the condition is more serious, there are respiratory difficulties, laryngeal edema, etc., then it is necessary to go to the hospital for emergency rescue. It is recommended to go to the hospital in time when the above mentioned symptoms occur, standardize the treatment, and follow the doctor’s instructions for medication, so as to avoid delaying the condition.