A rot outside the anus needs to be treated promptly, and you need to see what condition caused it first. You should go to the hospital to thoroughly disinfect the affected area. Use alcohol or hydrogen peroxide to clean the affected area, in order to do the affected area without secondary infection, and then local anesthesia, local debridement surgery. If it is a pus-filled eruption, drainage and debridement are needed. If it is caused by an anal fistula, it is necessary to make an endotomy and debridement or hang the thread therapy. After the operation, you need to carry out intravenous drip anti-infection treatment, and also need to pay attention to change the medicine on time. During the recovery period, you need to pay attention to the hygiene of the affected area, you can take a sitz bath or local cleaning to avoid infection. So when the anus outside the rot should be timely check what causes, and then according to the cause to take timely surgery for treatment.