Inflammatory bowel disease (IBD) is a long-term condition in which the immune system causes inflammation in the gut. With modern treatment and regular monitoring, most people lead full lives: working, studying, travelling and having families.

What is it?

IBD mainly refers to two conditions:

• Crohn's disease: can affect any part of the digestive tract from mouth to anus, most often the end of the small bowel and the colon. Inflammation can go through the full thickness of the bowel wall
• Ulcerative colitis: affects only the large bowel (colon and rectum), starting at the rectum and extending upwards continuously, involving the inner lining

IBD is not the same as irritable bowel syndrome (IBS). IBD causes visible inflammation and damage; IBS does not.

What causes it?

The exact cause is not known. IBD develops when the immune system reacts excessively to gut bacteria in people with a genetic tendency, influenced by environmental factors such as smoking (for Crohn's disease), diet and antibiotic exposure. It is not caused by stress or a single food, and it is not contagious.

Symptoms

• Diarrhoea, sometimes with blood or mucus
• Urgency to open the bowels, including at night
• Abdominal pain and cramping
• Tiredness, weight loss, anaemia
• In Crohn's disease: pain or discharge around the anus (fistula or abscess)
• Outside the bowel: joint pain, eye redness, skin lesions, mouth ulcers

How it is monitored

Symptoms alone are not a reliable guide, because inflammation can continue without them. Monitoring uses blood tests, the stool calprotectin test, colonoscopy, intestinal ultrasound and MRI. The goal is to control inflammation itself, not only symptoms, to prevent complications such as strictures, fistulas and surgery.

Treatment

Treatment depends on the type, extent and severity of the disease and is tailored to each person. Options include mesalazine (mainly for ulcerative colitis), short courses of steroids for flares, immunomodulators (azathioprine), biologics given by injection or infusion, and newer tablets. Surgery is sometimes the best option and can be life-changing. Separate sheets describe each medicine and test in detail.

Living with IBD

• Take your maintenance treatment even when you feel well; stopping treatment is one of the commonest causes of flares
• Stop smoking, especially with Crohn's disease
• Keep vaccinations up to date and check with your team before live vaccines
• Plan pregnancy with your team: being in remission at conception is the best protection for mother and baby
• Eat a varied diet; there is no single IBD diet, and unnecessary restriction can cause malnutrition

Common questions

This leaflet is general information and does not replace advice from your own doctor. Version 1.0, October 2026. Next review October 2028.