Patients with a bag on the buttocks that hurts when touched, the common causes are mainly the following: a. perianal abscess, mostly seen in acute purulent changes caused by bacterial infection of the perianal skin and anal sinusitis, at this time the patient’s skin will show obvious swelling, pain and elevated skin temperature, it is recommended that the patient improve the ultrasound examination, once the nature of the abscess is clear perform surgical incision and drainage as soon as possible, remove necrotic tissue from the trauma and strengthen Most patients can have their pain and infection controlled faster after 5-7 days of treatment. Second, epidermoid cysts combined with infection, because the skin of the buttocks is often in a humid environment, once accompanied by local pore blockage will cause local infection and obvious swelling and pain, patients need to apply local topical ichthyolipid ointment and ruyi gold ointment to promote faster absorption of local inflammation, and after the inflammation of the mass has completely subsided, it is recommended to perform complete surgical excision of sebaceous cysts to avoid recurrence of inflammation.