Overview
Inflammatory bowel disease is a term covering two chronic conditions: Crohn's disease and ulcerative colitis. Both cause persistent inflammation of the digestive tract. Ulcerative colitis affects the colon and rectum; Crohn's disease can affect any part of the gastrointestinal tract from mouth to anus. Both involve flares and remissions and require long-term management.
How common is it?
More than 500,000 people in the UK live with Crohn's disease or colitis. IBD can develop at any age, although it often starts in younger adults.
Causes and risk factors
IBD results from an abnormal immune response to gut bacteria in genetically susceptible individuals, triggered by environmental factors.
Common risk factors
- Genetic susceptibility (over 200 genetic variants identified, including NOD2)
- Dysregulated immune response to intestinal microbiome
- Smoking increases the risk and severity of Crohn's disease. It is not recommended to prevent or treat ulcerative colitis.
- Antibiotic use in early life
- Western diet, high in processed foods and low in fibre
- Urban living and hygiene hypothesis
- Appendicectomy for appendicitis has been associated with a lower risk of ulcerative colitis in some studies; this is not a reason for preventive surgery
- Stress (triggers flares rather than causing the condition)
Symptoms
- Persistent diarrhoea, often with blood or mucus
- Abdominal pain and cramping
- Urgency and frequency to open bowels
- Fatigue
- Unintentional weight loss
- Fever during flares
- Anaemia from chronic blood loss
- Crohn's: perianal disease, fistulae, mouth ulcers
- Extra-intestinal: joint pain, eye inflammation, skin rashes (erythema nodosum)
When to see a doctor
See a clinician for persistent bowel changes, blood in stools or unexplained weight loss. Frequent bloody diarrhoea with fever or feeling very unwell needs same-day urgent hospital assessment; contact your IBD team urgently. Severe abdominal pain, heavy or continuous bleeding, or collapse needs immediate emergency care.
Diagnosis
Colonoscopy with biopsies is the key diagnostic investigation. Faecal calprotectin is a non-invasive marker of intestinal inflammation. MRI small bowel for Crohn's extent. Blood tests assess inflammation, anaemia, and nutritional deficiencies.
Treatments
5-ASA drugs (mesalazine)
First-line for mild to moderate ulcerative colitis. Given orally and/or rectally. Maintain remission effectively with long-term use. Less effective in Crohn's disease.
Corticosteroids
Prednisolone or budesonide used to induce remission during flares. Not suitable for long-term use due to side effects. Intravenous steroids for severe flares.
Immunomodulators
Azathioprine, 6-mercaptopurine, or methotrexate used for maintenance of remission. Take 3 months to reach full effect. Regular blood monitoring required.
Biologics and small molecules
Anti-TNF agents (infliximab, adalimumab), vedolizumab, ustekinumab, and JAK inhibitors (tofacitinib, upadacitinib) for moderate to severe IBD not responding to conventional therapy. Highly effective at inducing and maintaining remission.
Surgery
Removing the colon and rectum can treat ulcerative colitis definitively, although surgery has consequences and some problems outside the bowel can remain. Surgery for Crohn's disease treats complications or severely affected bowel but does not cure the disease; the need varies.
Self-care and lifestyle
- Work with a dietitian to identify and manage dietary triggers
- Maintain adequate vitamin D, B12, folate, and iron (commonly deficient in IBD)
- Do not stop medication during remission without specialist advice
- Flu and pneumococcal vaccination is important as immunosuppressants increase infection risk
Prevention
There is no proven way to prevent IBD. A balanced diet and avoiding smoking support general health, but cannot guarantee prevention. Use antibiotics only as prescribed, rather than avoiding needed treatment.
Sources for targeted updates
Updated: 24 October 2026. Urgent-care guidance and the specific treatment or self-care statements corrected in this update; further corrections to urgent-care guidance, prevention, risk factors. This update covers the named sections; a full review of the remaining guide is pending.