Ulcerative Colitis Causes

While its exact causes are unknown, what is known is that ulcerative colitis (UC) is a chronic, or ongoing, inflammatory bowel disease (IBD) that primarily affects the large intestineThe lower part of the GI tract; the large intestine is wider and shorter than the small intestine and is typically divided into cecum, colon, and rectum. Much of the function of the large intestine is to reabsorb water and to form feces.. UC can also affect the eyes, skin, and joints. It is not contagious, nor is it caused by something you may have done or eaten.

Ulcerative colitis is thought to be a result of an interaction of factors

  • Heredity: Inherited genes may make you more susceptible to developing UC
  • The immune system: When triggered, it affects the large intestine, causing inflammation that contributes to symptoms
  • Environmental factors: Bacteria, a virus, or some unidentified factor in the environment that triggers an abnormal immune response

Foreign substances (antigens) in the environment may also be a cause of inflammation, or they may stimulate the body’s defenses to produce inflammation that continues without control.

Ulcerative colitis appears to be a result of different factors: heredity, the immune system, and environmental factors

UC is believed to be an overreaction of the immune system.

Researchers believe people with UC experience an overactive immune response. As a result, the large intestines become raw and inflamed (red and swollen)—chronically. This continuous, damaging inflammation leads to ulcerative colitis symptoms.

How your immune system works

  • The immune system is a complex network of cells that interact with each other to defend the body against foreign invaders
  • Circulating white blood cells patrol for foreign invaders, such as bacteria or viruses, “non-self” cells, which are considered dangerous
  • When the white blood cells find these invaders, they trigger an immune response called “inflammation” that results in the destruction and removal of the foreign substances

Inflammation: Your immune system’s weapon

  • Inflammation is your body’s weapon against foreign invaders, such as bacteria and viruses. White blood cells release molecules called “cytokines” —chemical messengers that promote inflammation
  • Inflammation helps the body limit the effects of the invader so it does not spread. Once the foreign invader is destroyed, inflammation goes away
  • Redness, swelling, and pain are all signs that inflammation is occurring in your body—and in ulcerative colitis, this inflammation is chronic (ongoing) unless controlled with an effective treatment plan

Whom does ulcerative colitis affect?

While UC most often starts between the ages of 15 and 30, it can affect people of any age.

Males and females appear to be affected equally. In addition, more people of Jewish-European ancestry develop UC than people from other groups.

Ulcerative colitis affects men and women equally

Understand Your Inflammation

Learn how it can play a role in your symptoms.

See Inside Inflammation

UC Tests and Diagnosis

Find out what tests are used to get diagnosed as well as for ongoing follow-ups.

Learn More

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