Diarrhoea usually occurs when fluid cannot be absorbed from the contents of your bowel, or when extra fluid is secreted into your bowel, causing watery faeces.
Short-term diarrhoea
Diarrhoea is usually a symptom of gastroenteritis (a bowel infection). It can be caused by:
- a virus, such as norovirus or rotavirus
- bacteria, such as campylobacter, Clostridium difficile (C. difficile), Escherichia coli (E. coli), salmonella and shigella – these may all cause food poisoning
- parasites, such as the Giardia intestinalis parasite that causes giardiasis
Diarrhoea caused by contaminated food or water while visiting a foreign country is often known as travellers’ diarrhoea.
Other possible causes of short-term diarrhoea include:
- emotional upset or anxiety
- drinking too much coffee or alcohol
- a food allergy
- appendicitis (painful swelling of the appendix)
- damage to the lining of the intestines due to radiotherapy
Medicines
Diarrhoea can also sometimes be a side effect of medicines, including:
- antibiotics
- antacid medicines that contain magnesium
- some medicines that are used in chemotherapy
- non-steroidal anti-inflammatory drugs (NSAIDs)
- selective serotonin reuptake inhibitors (SSRIs)
- statins (cholesterol-lowering medicines)
- laxatives (medicine used to help empty your bowels if you are constipated)
The patient information leaflet that comes with your medicine should state whether diarrhoea is a possible side effect.
You can also use the medicines A-Z to find out more about your medicine.
Long-term diarrhoea
Conditions that can cause persistent diarrhoea include:
- bowel cancer – this can cause diarrhoea and blood in your stools
- chronic pancreatitis – inflammation of the pancreas, a small organ that produces hormones and digestive juices
- coeliac disease – a digestive condition where you are intolerant to the protein gluten
- Crohn’s disease – a condition that causes inflammation of the digestive system lining
- irritable bowel syndrome (IBS) – a poorly understood condition where the normal functions of the bowel are disrupted
- microscopic colitis – a type of inflammatory bowel disease that causes watery diarrhoea
- ulcerative colitis – a condition that affects the colon (large intestine)
- cystic fibrosis – an inherited condition that affects the lungs and digestive system
Persistent diarrhoea can also sometimes occur following a gastrectomy. This is a surgical operation to remove part of the stomach, for example as a treatment for stomach cancer.
Diarrhoea can also sometimes be caused by bariatric surgery (weight loss surgery used as a last resort to treat people who are dangerously obese).
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