A large hard bag on the back may be related to boils, sebaceous cysts, lipomas, etc. Usually, medication and surgical excision can be chosen for treatment. 1. Boil: It is an acute purulent reaction of the hair follicle and its surrounding tissues, often manifested as a red, hemispherical painful nodule centered on the hair follicle, with a pus head in the center of the nodule. You can use topical mupirocin ointment, ichthyol ointment, oral cefuroxime, amoxicillin and other drugs. If there is abscess formation, it can also be incised and drained. 2. Sebaceous cysts: cystic swellings formed by sebaceous gland duct blockage, resulting in sebum retention. It is usually treated by surgical excision. If bacterial infection occurs, anti-infection treatment should be carried out first, and then surgery should be carried out after inflammation is controlled. 3. Lipoma: It is caused by the accumulation of mature fat tissue in the subcutaneous tissue of the back, which can also cause a big hard bag growing on the back, and usually does not need to be treated. If there are other discomforts or the tumor size is too large, surgical resection is needed. If the patient has a large hard bag on the back, it is recommended to go to the hospital in time to find out the cause of the disease, standardized treatment, so as not to delay the condition. Drugs need to be used in accordance with medical advice.