What should you know about common causes of diarrhea?

Gastroenteritis and food poisoning can cause sudden loose stools, cramps, nausea or vomiting, sometimes after contact with an infected person or contaminated food. Food intolerance may produce symptoms after a particular ingredient and often recurs with exposure. Persistent or recurring diarrhoea can occur with coeliac disease, Crohn's disease, irritable bowel syndrome or giardiasis. An overactive thyroid can also change bowel activity. The pattern, timing, travel history, medicines and other symptoms help a clinician narrow the possibilities.

Blood, mucus, fever, weight loss or pain may change the urgency of assessment. Diarrhoea itself does not identify one condition.

Drink frequent small amounts of water or oral rehydration fluid, especially after repeated stools. Eat simple foods when you feel able and wash hands carefully. Avoid preparing food for others while unwell. Seek advice before using anti-diarrhoeal medicine if you have blood in the stool, fever or severe pain. Persistent symptoms need assessment rather than repeated self-treatment.

Get urgent help for severe dehydration, fainting, confusion, severe abdominal pain, blood or black stools, or inability to keep fluids down. Arrange prompt medical advice for diarrhoea that keeps returning, follows recent travel or antibiotics, or affects a baby, older adult or person with a weakened immune system.

Ask whether your pattern suggests infection, intolerance or another digestive problem, whether a stool test is useful, how to replace fluids, and which warning signs should prompt reassessment.