Inflammatory bowel disease

Inflammatory bowel disease (IBD) is a term mainly used to describe two diseases, ulcerative colitis and Crohn's disease.

Information written and reviewed by Certified Doctors.



Inflammatory bowel disease (IBD) is a term mainly used to describe two diseases, ulcerative colitis and Crohn's disease.

Both ulcerative colitis and Crohn’s disease are long-term (chronic) diseases that involve inflammation of the gastrointestinal tract (gut).

Ulcerative colitis only affects the colon (large intestine), while Crohn’s disease can affect the entire digestive system, from the mouth to the anus.

It is sometimes difficult to tell the difference between the two main types of IBD. If this is the case, it is known as indeterminate colitis.

There are other, rarer types of IBD called collagenous colitis and lymphocytic colitis. Together these are often called microscopic colitis.

What are the symptoms?

The main symptoms of ulcerative colitis and Crohn’s disease are similar. They include:

Not everyone has all of these symptoms, and some people may experience additional symptoms, including nausea and fever.

The symptoms of IBD can come and go over long periods. People may experience periods of severe symptoms (flare-ups), and go through long periods when they have few or no symptoms at all (remission).

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The exact causes of ulcerative colitis and Crohn’s disease are unclear. It is thought that several factors may play a part, such as:

  • genetics - there is evidence that you are more likely to develop IBD if you have a close relative with the condition
  • disruption to the immune system (the body’s defence against infection) - inflammation may be caused by the immune system attacking healthy tissue inside the digestive system whilst fighting off a virus or bacteria

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There is currently no cure for ulcerative colitis or Crohn's disease. Treatment aims to relieve symptoms and prevent them from returning.

Mild ulcerative colitis may not need treatment as symptoms can clear up after a few days.

Medications used to treat ulcerative colitis or Crohn's disease may include:

  • aminosalicylates, or in more severe cases, corticosteroids - to reduce inflammation
  • immunosuppressants - to block the harmful activities of the immune system

An estimated 20% of people with ulcerative colitis have severe symptoms that often don't respond to medication. In these cases, it may be necessary to surgically remove an inflamed section of the digestive system.

Around 60-75% of people with Crohn’s disease will require surgery to repair damage to their digestive system and treat complications of the condition.

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Who is affected?

IBD is usually diagnosed in people in their late teens or early 20s, but it can appear at any age.

IBD is more common in white people than in black people or those of Asian origin. The condition is most prevalent among Jewish people of European origin.

IBD affects slightly more women than men.

Want to know more?

  • NACC: Inflammatory Bowel Disease Basics
  • Core: What is Crohn’s disease? (PDF, 145kb)
  • Core: What is ulcerative colitis? (PDF, 107kb)
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