The anal skin is considered to be caused by external hemorrhoids, perianal abscesses, anal papillomas and other conditions. 1. External hemorrhoids: usually due to perianal skin or subcutaneous tissue inflammation, perianal venous thrombosis, perianal connective tissue hyperplasia and other conditions, but also with poor dietary habits, alcohol consumption, lifestyle and other factors. Patients often appear pain, foreign body sensation, anal swelling, blood in stool and other symptoms, and all types of external hemorrhoids have anal swelling, visible to the naked eye, which will appear anal skin. 2. Perianal abscess: it is mainly caused by the infection of anal crypt, and also related to AIDS, diabetes, radiotherapy and any other factors that lead to low resistance. Patients often appear perianal subcutaneous abscess, sciatic rectal fossa abscess, etc., and sciatic rectal fossa abscess is often manifested as huge redness and swelling of the outer part of anus, which can also be manifested as anal skin flap. 3. Anal papilloma: this disease is mainly benign tumor disease occurring in anal canal, mostly caused by trauma, chronic inflammation, feces and other factors of repeated stimulation. Patients often appear pain, anal itching, defecation and other symptoms, and prolapse of anal papilloma can not be returned to the case, will also occur incarceration, can also appear anal skin phenomenon. When there is anal skin, it is recommended that the patient consult a doctor for examination in a timely manner to clarify the cause of the disease, and strictly comply with the doctor’s instructions to carry out targeted treatment, so as to avoid delays in the condition.