Red rash after MMR vaccination is mainly considered to be caused by allergy, which can be handled according to the severity of the condition by strengthening observation, general treatment and medication. 1. Enhanced observation: For patients with mild rash, observation should be strengthened. If any abnormal situation occurs, it should be treated by doctor in time. 2. General treatment: During the waiting period, keep the affected area clean and dry, and avoid scratching the affected area with hands. 3. Medication: For patients with severe rashes, apply loratadine, benadryl and other medications under the guidance of doctors. After the use of drugs, nausea, abdominal pain, vomiting and other adverse reactions, must seek medical treatment as soon as possible. Symptoms of rash after vaccination should be taken seriously, observed more closely, and medical help sought. If special medical intervention is required, medical advice must be followed.