The anus is the opening at the end of your anal canal. The rectum sits between your colon and anus and acts as a holding chamber for stool. When pressure in your rectum becomes too great, the internal ring of muscle called the anal sphincter relaxes to allow stool to pass through your anal canal, the anus, and out of your body.

The anus consists of glands, ducts, blood vessels, mucus, tissues, and nerve endings that can be highly sensitive to pain, irritation, and other sensations. Depending on the cause, a swollen anus can feel warm, cause sharp or burning pain (especially after a bowel movement), and even produce bleeding and pus.

Anal swelling can have a number of causes. Most of them aren’t concerning but some can be serious. See a doctor immediately if you have:

  • rectal bleeding that won’t stop
  • severe pain
  • fever
  • anal discharge

The cause may be harmless or it may signal something life-threatening, such as cancer. Typical causes of anal swelling are:

Anusitis

This is a common disorder. It usually involves inflammation of the anal lining and is often misdiagnosed as hemorrhoids. Symptoms include pain and a wet, sometimes bloody discharge. Anusitis is commonly caused by:

  • an acidic diet including coffee and citrus
  • stress
  • excessive diarrhea

External hemorrhoids

External hemorrhoids are swollen blood vessels in the mucosal lining of the anus. They’re common, affecting 3 out of 4 adults. They may result from:

  • straining during a bowel movement
  • low-fiber diet
  • chronic diarrhea or constipation

External hemorrhoids can appear as a lump and may be painful and bleed, though some hemorrhoids don’t produce any discomfort.

Anal fissure

An anal fissure is a tear in the lining of the anal canal. It’s caused by:

  • hard bowel movements
  • chronic diarrhea
  • irritable bowel syndrome
  • tight anal sphincter muscle
  • anal tumors or infections, rarely

Anal fissures are common and are often mistaken for hemorrhoids. They can cause:

  • pain during a bowel movement that lasts for up to a few hours
  • bleeding
  • lump near the fissure

Anal abscess

When a gland in the anus becomes clogged and then infected, it can produce an anal abscess. This is technically defined as a collection of pus around inflamed tissue. It can produce:

  • pain
  • swelling
  • lump around the anus
  • fever

According to Harvard Health, more than half of anal abscesses occur in people between ages 20 to 40. Men are also more commonly affected than women.

The gland becomes infected when bacteria, fecal matter, or foreign material invades through tiny cracks. Certain conditions, such as colitis, can increase your risk.

Anal fistula

This is a tunnel that forms inside the anus and exits through the skin on the buttocks. According to Swedish Medical Center in Seattle, half of those who have had an anal abscess will develop a fistula. Symptoms include:

  • anal swelling
  • irritation
  • pain
  • itching
  • stool leakage

Perianal Crohn’s disease

Crohn’s disease is a hereditary condition that causes chronic inflammation of the digestive tract. Most of the time it affects the small intestine, but it can affect the entire digestive tract, including the anus.

According to a 2017 article, up to 43 percent of people with Crohn’s have perianal Crohn’s. Symptoms include anal fissures and fistulas.

Anal sex and play

Anal swelling can occur after rough anal sex or insertion of a sex toy into the anus.

The rectum is connected to the anus via the narrow anal canal. Given their close proximity, it makes sense that what causes swelling in the anus can also cause swelling in the rectum. Conditions that can cause rectal and anal swelling include:

Conditions like hemorrhoids can often be seen visually or felt when a doctor inserts a gloved finger into your anal canal through a digital exam. Fissures or fistulas that aren’t apparent from visual inspection can be identified via:

  • Anoscopy. This is a tube with a light on the end that allows your doctor to see inside the anus and rectum.
  • Flexible sigmoidoscopy. This procedure, using a flexible tube with a light and camera, allows your doctor to look closely at the rectum and lower intestinal tract to see if something like Crohn’s disease is contributing to your symptoms.
  • Colonoscopy. This is a procedure that uses a long, flexible tube with a camera inserted into the anus to allow viewing of the rectum and colon. This is generally used to rule out cancer.

Treatment varies by diagnosis.

Anusitis

  • dietary changes, including removing foods that irritate the digestive tract
  • stress reduction
  • icing the area by wrapping ice in a towel
  • creams with numbing agents
  • hydrocortisone cream to combat swelling
  • warm sitz baths by soaking for 20 minutes two to three times a day
  • ice
  • adding 25 to 35 grams of fiber to your diet per day, including fresh fruits and vegetables, whole grains, and beans
  • high-fiber diet
  • OTC stool softeners
  • warm baths
  • lidocaine cream

External hemorrhoids

Anal fissure

In an older study, 89 percent of people with uncomplicated anal fissures were successfully treated with Botox injections, which help relax the anal sphincter.

Anal abscess

Surgical drainage is considered the most effective treatment. Antibiotics may be recommended for those with underlying diseases, such as diabetes, and those who have a suppressed immune system.

Anal fistula

The fistula’s tunnel may be opened, plugged, or tied off with surgery.

Perianal Crohn’s disease

  • antibiotics
  • surgery
  • periodic icing
  • warm baths
  • OTC pain relievers and anti-inflammatories

Anal sex

Get immediate medical attention if you have:

  • anal bleeding that won’t stop, especially if you feel dizzy or lightheaded
  • increasing pain
  • anal pain with a fever or chills

See a doctor if you have anal pain and:

In most cases, anal swelling is more uncomfortable than dangerous. Try at-home measures like over-the-counter numbing creams, a high-fiber diet, pain relievers, and warm baths.

If you don’t find relief, talk to a doctor about medical treatments that can help reduce anal swelling and get you on the road to recovery.