Acute diarrhoea is usually caused by a viral or bacterial infection and affects almost everyone from time to time. A common cause in both children and adults is gastroenteritis, an infection of the bowel.
Bouts of diarrhoea in adults may also be brought on by anxiety or drinking too much coffee or alcohol. Diarrhoea may also be a side effect of a medication.
NHS
Symptoms, causes, treatment and information
Macmillan Cancer Support
Diarrhoea as a result of cancer treatments