There are three main cases of very smelly anus: first, mainly due to the failure to clean the anus in time after a bowel movement resulting in residual stool around the anus, resulting in a very smelly anus. Second, perianal abscess, an acute purulent infection of the perianal space of the rectum. It shows as redness and swelling around the anus, often with severe pain. When the abscess breaks down there is a foul odor around the anus and is accompanied by pus or fluid flowing from the anus. Third, anal fistula is often secondary to rectal perianal abscess, which manifests as intermittent fecal or intestinal fluid flow around the anus, and can be palpated in the anus as a stripe-like mass. The fourth, when the hemorrhoids fall off to form embedded hemorrhoids or thrombosed external hemorrhoids, can also appear very smelly anal phenomenon. When the anus is smelly, you should go to a regular hospital in time to clarify the cause and actively cooperate with the specialist for treatment.