Most causes of anal swelling are benign, but some can be more serious. Learn about the causes of anal swelling and what treatment options are available. Most causes of a swollen anus are temporary and harmless, but some require medical attention. anal bleeding is one of the most common causes of swelling. Anal bleeding may come from the anus itself or may appear when blood is mixed with a persons stools. There are many reasons a person may have bleeding from the anus, including inflammatory bowel disease, rectal cancer, constipation , and ulcers. This section discusses 17 medical conditions causing anal swelling. A simple discussion of these causes with additional information is below. Causes of anal swelling the following medical conditions are some of the possible causes of anal swelling. There are likely to be other possible causes, so ask your doctor about your symptoms. Most anal abscesses are a result of infection from small anal glands. This often appears as a painful boil-like swelling near the anus. Are you experiencing swelling in your anus? A swollen anus may actually be due to a swollen rectum, since the two parts of the body are so closely related. Anal and rectal swelling range in severity, from common conditions that you can treat at home, such as hemorrhoids, to conditions that require a doctors care, such as cellulitis. Read more below to learn what may be causing swelling around.