A growth under the buttocks hurts when pressed is usually caused by sebaceous cyst infection, perianal abscess and folliculitis. Patients can follow the doctor’s instructions through oral medication, local application and surgical drainage for treatment. 1. Sebaceous cyst infection: cysts are formed when sebaceous ducts are blocked, but cysts are easily infected by pathogenic bacteria. Patients can be treated with oral antibiotics, such as amoxicillin capsules and ceftazidime capsules. If sebaceous cysts are large, they need to be treated by surgical removal of the cysts. 2. Perianal abscess: When bacterial infection occurs around the anal canal and rectum, it can lead to acute suppuration and formation of perianal abscess, resulting in a hard and painful bag under the buttocks. You can take metronidazole tablets and cefixime capsules orally for treatment. At the same time, you need to incise the abscess area to drain out the pus inside. 3. Folliculitis: it occurs because of bacterial infection around the hair follicle, resulting in inflammation. Patients can apply topical mupirocin ointment, fusidic acid cream and other ointments. When the folliculitis further develops into pus, surgical incision should be used to drain the pus, and at the same time, oral antibiotics such as cefuroxime tablets and other drugs for anti-infection treatment. Patients with the above symptoms, should go to the hospital in a timely manner, by the doctor to identify the cause of the symptomatic treatment, do not self-medication, to avoid delays in the condition of the adverse consequences.