Redness and swelling of the anus without pain may be internal hemorrhoids, rectal prolapse, anal fistula or chronic anal fissure and other perianal diseases, or may be due to the irritation of digestive juices. 1. Internal hemorrhoids: after the occurrence of internal hemorrhoids, the anus may prolapse swelling, sometimes local redness and swelling, internal hemorrhoids symptoms are mainly blood in the stool, and fresh blood, usually without pain. 2. Rectal prolapse: after the occurrence of rectal prolapse, the anus will also come out of the swelling, the local blood circulation will be affected, there may be redness and swelling, but usually no pain. 3. Stimulation of digestive juices: If diarrhea and other diseases occur, digestive juices will have an irritating effect on the anus, which will lead to local redness and swelling, and sometimes itching, but usually no pain. It is recommended that patients go to the hospital, need to improve the relevant examination, such as anoscopy, stool routine, etc., usually can clarify the cause.