Patients with hyperthyroidism who receive iodine-131 radiation therapy may experience adverse reactions such as radiation thyroiditis, which can cause swelling and pain in the neck and under the ears. In case of radiation thyroiditis, the vast majority of patients are treated with glucocorticosteroids which are highly effective and provide rapid relief of symptoms, and it is recommended that the medication be used as prescribed by the doctor. The short-term reaction to iodine 131 treatment is mild, with swelling and pain in the thyroid area, which is a common reaction. Some patients can be self-healed, if the pain is not obvious, no special treatment is needed. If radioactive thyroiditis occurs after drinking iodine 131, a small number of patients may have more severe pain that cannot be tolerated, and glucocorticosteroids such as prednisolone can be chosen to relieve the pain. In addition, if you have swelling and pain under the ear in response to drinking iodine 131, you can also choose to go to the nearest medical institution for an interview and treatment.