Causes

Diarrhoea usually occurs when fluid can't be absorbed from the contents ofyour bowel, or when extra fluid is secreted into your bowel, causing watery poo.

Short-term diarrhoea

Diarrhoea is usually a symptom of a bowel infection (gastroenteritis) , whichcanbe caused by:

• a virus such as norovirus orrotavirus
• bacteria such as campylobacter, Clostridium difficile (C. difficile) , Escherichia coli (E. coli), salmonella or shigella; these can all cause food poisoning
• parasites such as the Giardia intestinalis parasite that causes giardiasis

Other possible causes ofshort-term diarrhoea include:

• feelings ofanxiety
• drinking too much alcohol
• a food allergy
• appendicitis
• damage to the lining of the intestines as a result of radiotherapy

Medicines

Diarrhoea can also sometimes be a side effect of a medication, including:

• antibiotics
• antacid medicines that contain magnesium
• some chemotherapy medicines
• non-steroidal anti-inflammatory drugs (NSAIDs)
• selective serotonin reuptake inhibitors (SSRIs)
• statins cholesterol-lowering medicines
• laxatives medicine used tohelp empty your bowels

The patient information leaflet that comes with your medicine should state whether diarrhoea is a possible side effect.

Long-term diarrhoea

Conditions that can cause persistent diarrhoea include:

• irritable bowel syndrome (IBS) a poorly understood condition that affects the normal functions of the bowel
• inflammatory bowel disease conditions that cause the gut to become inflamed, such as Crohn's disease and ulcerative colitis
• coeliac disease a digestive condition where you have an adverse reaction to gluten
• bile acid malabsorption where bile produced by the liver builds up in the digestive system
• chronic pancreatitis inflammation of the pancreas
• diverticular disease where small bulges or pockets develop in the lining of the intestine
• bowel cancer this can cause diarrhoea and blood in your stools

Persistent diarrhoea can also sometimes occurafter surgery on the stomach, such as a gastrectomy .