Insulin is a hypoglycemic hormone and an effective way to control blood sugar in diabetic patients. There are many types of insulin, and the use of insulin requires the selection of a suitable treatment plan under the guidance of a doctor and according to the patient’s weight, blood sugar and complications. If patients have itchy skin and bumps after insulin, the following points should be noted: i. It is recommended to change the injection site to exclude local irritation caused by repeated injections. Second, pay attention to the replacement of insulin injection needles, which are single-use devices and cannot be reused. Third, it is recommended that the patient visit the dermatology department and apply anti-allergy medication if necessary. If it is determined that the patient is allergic to insulin, it is recommended to change to another insulin treatment plan under the guidance of a doctor, as the patient may not be allergic to all insulins. V. Pay attention to regular rechecking of blood glucose and glycated hemoglobin.