The growth of a bag on the buttocks may be caused by boils, carbuncles and lipomas. 1. Boils: Boils are mostly related to Staphylococcus aureus infection, and may be triggered by skin diseases, high temperature and trauma, etc. Red, hemispherical nodules like peas will appear on the skin of the patient, accompanied by painful symptoms, which are commonly seen in the neck and buttocks, etc. Carbuncles: Carbuncles may be caused by Staphylococcus aureus infection. 2. Carbuncle: the onset of carbuncle may be caused by Staphylococcus aureus infection, sweating, scratching, high temperature and other factors may trigger the disease, the patient’s affected area will appear red, swollen and painful inflammatory hard lumps, the diameter of 3~10cm, most commonly found in the back, shoulders, buttocks and other places. 3. Lipoma: the incidence of lipoma may be caused by the stimulation of tumor-causing factors, and the disease may also be induced by abnormalities of systemic lipid metabolism, heredity and other factors. Any part of the patient’s fatty tissue may be affected, mainly manifested as localized lumps, mostly seen in thighs, buttocks, neck and shoulders. There are more reasons that lead to the growth of large bags on the buttocks, it is recommended that patients go to regular hospitals to clarify the cause of the disease.