1. What you can do right now
Quick help with acute diarrhoea
- Drink: plenty of fluids – best of all an oral rehydration solution (ORS) from the pharmacy. Water, unsweetened tea or clear broth are alternatives.
- Bland diet: rusks, boiled rice, banana, grated apple, carrot soup – easy to digest.
- Avoid irritants: no alcohol, no coffee, no fatty foods, no raw vegetables.
- Loperamide: only sensible short-term with acute diarrhoea without fever and without blood in the stool – not in children under 12 years.
- Check medications: antibiotics, metformin, magnesium preparations and NSAIDs can trigger diarrhoea.
See a doctor immediately!
With bloody or black stool, high fever (over 39 °C), severe abdominal pain, signs of dehydration (dark urine, dizziness, skin folds that remain standing) or diarrhoea in infants, toddlers or older people, seek medical help immediately. With acute circulatory failure, call the emergency number 112 (in the US: 911)!
2. Understanding diarrhoea – what happens in the body?
We speak of diarrhoea when the stool is unformed, watery or mushy and is passed more than three times a day. Diarrhoea is not a condition in its own right but a symptom – the causes range from harmless gastrointestinal infections to chronic bowel diseases.
Acute diarrhoea (under two weeks) is usually triggered by gastrointestinal infections, spoiled food or medications. If the diarrhoea lasts longer than four weeks, doctors speak of chronic diarrhoea – and it is worth searching specifically for the cause. Decisive in both cases: the body must get enough fluid and electrolytes, otherwise a dangerous dehydration threatens.
A simple self-test: skin fold test and urine colour
If you lift a fold of skin on the back of your hand and it remains standing instead of springing back at once, that is a sign of fluid deficiency. Dark-yellow, strong-smelling urine and a dry mouth also point to dehydration – then it is essential to drink more, best of all ORS.
3. Common causes of diarrhoea
3.1 Acute diarrhoea (under two weeks)
Gastrointestinal infection (gastroenteritis): by far the most common cause. Viruses (above all noroviruses, rotaviruses) or bacteria (e.g. salmonella, campylobacter, E. coli) trigger watery stools, nausea, vomiting and abdominal cramps. Colloquially, gastric flu.
Food poisoning: food contaminated by bacterial toxins (e.g. Staphylococcus aureus, Bacillus cereus). Symptoms often begin within a few hours after eating.
Traveller's diarrhoea: a bacterial infection through unfamiliar germs in drinking water or food – it affects a considerable proportion of all long-haul travellers. More: Medications when travelling.
Stress and agitation: acute stress can speed up bowel movement and trigger diarrhoea – it is often underestimated.
Alcohol: it irritates the intestinal mucosa and disrupts water absorption in the gut.
3.2 Chronic diarrhoea (over four weeks)
Irritable bowel syndrome: the most common cause of chronic diarrhoea in young adults. A functional bowel disorder with changing bowel habits, bloating and abdominal cramps.
Inflammatory bowel disease: Crohn's disease and ulcerative colitis – usually with bloody or mucousy diarrhoea, abdominal pain and weight loss.
Coeliac disease: gluten intolerance – diarrhoea, bloating, tiredness and deficiency symptoms. It is often recognised only late.
Food intolerances: lactose intolerance (milk sugar), fructose malabsorption (fruit sugar), sorbitol intolerance – diarrhoea in each case after consuming certain foods.
Overactive thyroid: it speeds up the bowel transit and can cause chronic diarrhoea.
Microscopic colitis: a frequently overlooked cause of watery chronic diarrhoea, especially in older women. The intestinal mucosa looks normal at colonoscopy – only the tissue sample shows the inflammation.
4. Diarrhoea in children and infants
In infants and toddlers, diarrhoea is to be taken particularly seriously, because the small body dehydrates faster than in adults. Watch for the following signs of dehydration: a dry nappy (fewer than six wet nappies a day in infants), a sunken fontanelle, dry lips, listlessness or crying without tears.
Oral rehydration solutions (ORS) from the pharmacy are the treatment of choice – not cola, not pretzel sticks. Breastfeeding or formula milk should be continued during the diarrhoea. Loperamide is generally not recommended in children under twelve years. In infants under six months with diarrhoea, a medical review is generally always advised.
Infants and toddlers: when in doubt, see a doctor
In infants and small children, dehydration can become dangerous within a few hours. Better to go to the paediatrician or the emergency department once too often than too late.
5. Treating diarrhoea – what really helps
Fluid and electrolytes
The most important thing with diarrhoea. Drink plenty of water, unsweetened tea or clear broth. With more severe or persistent diarrhoea, oral rehydration solutions (glucose-electrolyte mixtures) from the pharmacy are sensible – they replace water, salts and sugar in the right composition.
Bland diet
Easily digestible foods such as rusks, boiled rice, grated apple, bananas, carrot soup or toast. The old BRAT diet (banana, rice, apple, toast) is not strictly evidence-based but does no harm. More important than the choice of foods is sufficient fluid intake.
What to avoid?
Very fatty foods, raw vegetables, alcohol, coffee, dairy products (if lactose intolerance is suspected) and very sugary or carbonated drinks can intensify the diarrhoea.
Cola and pretzel sticks are not recommended
The old tip is outdated: cola contains too much sugar and too little sodium, pretzel sticks provide only sodium without potassium. Oral rehydration solutions from the pharmacy are clearly better – they have the right ratio of water, salts and glucose.
With bloody stool, high fever, severe dehydration or diarrhoea in infants, seek medical help immediately!
