Methimazole is a medication used to treat hyperthyroidism, and if an allergy to said medication occurs, immediate desensitization is required at this time. If the degree of allergy is not serious and belongs to mild allergy, but if there is itching of the skin, red rashes, blotchy rashes, maculopapular rashes on the body, or physical discomfort, such as tightness of the chest, shortness of breath, palpitations, it is necessary to go to the hospital for desensitization treatment immediately. Injectable drugs such as methylprednisolone and methylprednisolone can be applied for symptomatic and desensitizing treatment, and oral anti-allergic drugs can also be taken for treatment. In case of severe allergy, epinephrine can be applied, and the patient should be given a large amount of rehydration, and blood pressure, oxygen saturation heart rate, cardiac function and other monitoring should also be carried out.