Diarrhoea: Causes, Treatment, Dehydration Signs and Prevention

Diarrhoea is extremely common, but it should not always be dismissed as a minor stomach problem.

For many otherwise healthy adults, an episode of acute diarrhoea improves within a few days. However, diarrhoea can become dangerous when the body loses too much water and electrolytes, leading to dehydration.

Babies, young children, older adults and people with certain medical conditions can become seriously ill more quickly.

The most important immediate goal is therefore not simply to “stop” every bowel movement.

It is to:

• replace lost fluids and electrolytes,
• prevent dehydration,
• continue appropriate nutrition,
• identify warning signs,
• and treat the underlying cause when necessary.

What Is Diarrhoea?

Diarrhoea generally means passing three or more loose or watery stools in a day, or passing loose stools more frequently than is normal for you.

Simply passing formed stools several times a day is not necessarily diarrhoea.

Likewise, normal loose stools in breastfed babies should not automatically be classified as diarrhoea.

Acute, Persistent and Chronic Diarrhoea

Not every episode of diarrhoea is the same.

Acute diarrhoea

Acute diarrhoea begins suddenly and commonly lasts a few days.

According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), acute diarrhoea typically lasts less than one week.

Common causes include:

• viral gastroenteritis,
• food poisoning,
• and side effects of medicines.

Persistent diarrhoea

Persistent diarrhoea continues for more than two weeks but less than four weeks.

Chronic diarrhoea

Chronic diarrhoea generally lasts four weeks or longer or repeatedly comes and goes over an extended period.

Chronic diarrhoea needs proper investigation because the causes can be very different from a short episode of infectious diarrhoea.

What Causes Acute Diarrhoea?

Infections are among the most common causes.

They can be caused by:

• viruses,
• bacteria,
• or parasites.

These microorganisms may spread through:

• contaminated food,
• contaminated drinking water,
• poor hand hygiene,
• contaminated surfaces,
• or close contact with an infected person.

Viral Gastroenteritis

Viral gastroenteritis is a common cause of acute diarrhoea.

Viruses that can cause gastroenteritis include:

• norovirus,
• rotavirus,
• adenovirus,
• and astrovirus.

Symptoms may include:

• watery diarrhoea,
• abdominal cramps,
• nausea,
• vomiting,
• and sometimes fever.

The term “stomach flu” is sometimes used for viral gastroenteritis, but influenza viruses do not cause ordinary viral gastroenteritis.

Food Poisoning

Food poisoning can result from eating or drinking something contaminated with harmful microorganisms or their toxins.

Possible organisms include certain strains or species of:

• Salmonella,
• Campylobacter,
• Escherichia coli (E. coli),
• Staphylococcus aureus,
• Clostridium perfringens,
• and many others.

Food can become contaminated during:

• production,
• processing,
• transport,
• preparation,
• cooking,
• or storage.

Parasites Can Also Cause Diarrhoea

Parasites are another possible cause.

For example, Cryptosporidium can spread through contaminated water and can cause watery diarrhoea.

Other parasitic infections may occur depending on:

• geographic location,
• sanitation,
• travel,
• water quality,
• and exposure.

Persistent diarrhoea after travel may therefore require professional assessment.

Medicines Can Cause Diarrhoea

Not all diarrhoea is caused by an infection.

Medicines can also cause it.

Examples include some:

• antibiotics,
• antacids containing magnesium,
• cancer treatments,
• laxatives,
• and other medicines.

Antibiotics can also alter the intestinal microbiome and increase the risk of infection with Clostridioides difficile (C. difficile) in some people.

If significant diarrhoea develops during or after antibiotic treatment, seek medical advice rather than simply treating the symptom yourself.

Food Intolerances Can Cause Diarrhoea

Some people develop diarrhoea because they cannot properly digest particular substances.

Examples include:

Lactose intolerance

Lactose is the natural sugar in milk and dairy products.

People with lactose intolerance may develop:

• diarrhoea,
• bloating,
• abdominal discomfort,
• and gas

after consuming lactose.

Fructose intolerance or malabsorption

Some people have difficulty absorbing fructose, a sugar found naturally in fruit and honey and added to many drinks and processed foods.

Sugar alcohols

Sweeteners such as:

• sorbitol,
• mannitol,
• and xylitol

can cause diarrhoea in some people, particularly when consumed in large quantities.

These are often found in sugar-free sweets, chewing gum and other products.

Digestive Conditions Can Cause Chronic Diarrhoea

Long-lasting or recurrent diarrhoea may be associated with conditions such as:

• irritable bowel syndrome (IBS),
• inflammatory bowel disease,
• Crohn's disease,
• ulcerative colitis,
• coeliac disease,
• pancreatic disorders,
• small intestinal bacterial overgrowth,
• and other digestive conditions.

Diarrhoea can also occur after certain abdominal operations.

Persistent symptoms therefore should not automatically be treated as a simple infection.

What Are the Symptoms of Diarrhoea?

The defining symptom is frequent loose or watery stools.

Other symptoms can include:

• urgent need to use the toilet,
• abdominal cramps,
• abdominal pain,
• nausea,
• vomiting,
• fever,
• bloating,
• and loss of bowel control.

Certain infections may also cause:

• blood in the stool,
• mucus or pus,
• fever,
• chills,
• dizziness,
• or more severe abdominal pain.

The Biggest Immediate Danger: Dehydration

Diarrhoea causes the body to lose both water and electrolytes.

Electrolytes are minerals such as sodium and potassium that are important for normal body function.

If these losses are not replaced, dehydration can develop.

Severe dehydration can be life-threatening.

This is particularly important in infants and young children, who can deteriorate rapidly.

Signs of Dehydration in Adults

Watch for:

• excessive thirst,
• dry mouth,
• urinating less frequently,
• dark-coloured urine,
• tiredness,
• dizziness,
• light-headedness,
• sunken eyes,
• and weakness.

Severe dehydration may cause:

• confusion,
• fainting,
• very little or no urine,
• rapid heartbeat,
• and signs of shock.

These require urgent medical attention.

Signs of Dehydration in Babies and Children

Children can become dehydrated more quickly than adults.

Warning signs may include:

• fewer wet nappies/diapers,
• no wet diaper for several hours,
• dry mouth,
• no tears when crying,
• sunken eyes or cheeks,
• unusual sleepiness,
• irritability,
• poor feeding,
• and reduced activity.

A baby or young child with significant diarrhoea or signs of dehydration should be assessed promptly.

Oral Rehydration Solution Can Save Lives

One of the most important treatments for diarrhoea is oral rehydration solution (ORS).

ORS contains a carefully balanced mixture of:

• clean water,
• glucose,
• and electrolytes.

The glucose helps the intestine absorb sodium and water efficiently.

ORS does not necessarily stop the diarrhoea immediately.

Instead, its crucial purpose is to replace the water and salts being lost and prevent or treat dehydration.

Why ORS Is Better Than Plain Water in Significant Diarrhoea

Plain water replaces fluid, but it does not replace electrolytes in the same balanced way as properly prepared ORS.

For significant diarrhoea—especially in children, older adults or people developing dehydration—commercially prepared ORS can be particularly valuable.

Use ORS according to the packet instructions.

Do not make it stronger or weaker than directed.

Don't Guess the Amount of Water for an ORS Sachet

Different ORS products may be formulated for different amounts of water.

Always read the instructions.

Using too little water can make the solution too concentrated.

Using too much water can make it too dilute.

If you are uncertain, ask a pharmacist or healthcare professional.

Can Homemade ORS Be Used?

Where commercially prepared ORS is unavailable, WHO recognizes oral rehydration based on clean water, salt and sugar as an important life-saving intervention.

However, measurement errors can make homemade mixtures unsafe.

Whenever possible, use a properly manufactured ORS sachet and follow its preparation instructions exactly.

If commercial ORS is unavailable and dehydration is a concern, obtain local healthcare guidance on the recommended home preparation used in your country rather than guessing the quantities.

What Should Adults Drink?

Most adults with mild acute diarrhoea should drink enough fluid to replace what they are losing.

Suitable options can include:

• water,
• oral rehydration solution,
• broth,
• and other appropriate fluids.

If you are vomiting, try taking small, frequent sips rather than drinking a large amount at once.

People with severe diarrhoea or signs of dehydration may benefit particularly from ORS.

Special Considerations for Some Medical Conditions

People with conditions such as:

• kidney disease,
• heart disease,
• diabetes,
• or other illnesses affecting fluid or electrolyte balance

may need individualized advice about the amount and type of fluid they should consume.

If you have one of these conditions and develop significant diarrhoea, contact your healthcare professional.

Should You Stop Eating?

Usually, no.

The old idea that people should “starve” diarrhoea is not good general advice.

When your appetite returns, most people can resume their normal diet.

Children should generally continue receiving appropriate nutritious food.

Breastfed babies should normally continue breastfeeding.

Formula-fed infants should generally continue their normal feeding unless a healthcare professional advises otherwise.

What Foods Can You Eat?

There is no single mandatory “diarrhoea diet.”

Choose foods that you can tolerate.

Examples may include:

• rice,
• potatoes,
• bread,
• oats,
• bananas,
• soups,
• vegetables,
• eggs,
• lean protein,
• and other familiar foods.

The priority is maintaining hydration and adequate nutrition rather than following an unnecessarily restrictive diet.

Do You Need the BRAT Diet?

The traditional **BRAT diet—bananas, rice, applesauce and toast—**is sometimes recommended for diarrhoea.

These foods can be eaten if tolerated, but there is generally no need to restrict yourself only to these four foods.

A very restrictive diet may not provide adequate nutrition, particularly for children.

Should You Avoid Dairy Products?

Not everyone with diarrhoea needs to avoid dairy.

However, some people temporarily have difficulty digesting lactose after a gastrointestinal infection.

If milk or dairy clearly worsens your diarrhoea, bloating or cramps, temporarily reducing lactose may help.

Persistent problems should be discussed with a healthcare professional.

What About Sugary Drinks?

Very sugary drinks may worsen diarrhoea in some situations because large amounts of sugar can draw additional water into the intestine.

They are not a substitute for properly formulated ORS when significant rehydration is needed.

Can Adults Take Anti-Diarrhoeal Medicine?

Some adults with uncomplicated acute watery diarrhoea may use over-the-counter medicines such as loperamide.

However, these medicines are not appropriate for everyone.

Do not simply suppress diarrhoea when there are warning signs suggesting a potentially serious infection.

When Should Loperamide Be Avoided?

Seek professional advice rather than self-treating with loperamide if you have:

• blood in the stool,
• high fever,
• severe abdominal pain,
• suspected severe infection,
• or significant diarrhoea associated with antibiotic use.

Anti-diarrhoeal medicines are generally not routinely recommended for infants and young children without professional advice.

Always follow local medication guidance and product instructions.

Do You Need Antibiotics?

Usually not.

Many cases of acute diarrhoea are caused by viruses and improve without antibiotics.

Antibiotics do not treat viral gastroenteritis.

They may be appropriate for certain bacterial or parasitic infections, but the decision depends on:

• the suspected organism,
• severity,
• patient risk factors,
• travel history,
• laboratory results when needed,
• and local antimicrobial resistance.

Unnecessary antibiotic use can cause side effects and contribute to antimicrobial resistance.

Don't Use Leftover Antibiotics

Do not use leftover antibiotics from a previous illness or another person's prescription to treat diarrhoea.

The wrong antibiotic may:

• be ineffective,
• cause side effects,
• disrupt normal intestinal bacteria,
• increase the risk of C. difficile infection,
• and contribute to antibiotic resistance.

What About Zinc for Children?

WHO recommends zinc supplementation as part of the management of acute diarrhoea in children in relevant settings.

WHO guidance describes a 10–14 day course and age-based dosing.

Because formulations and national recommendations can differ, parents and caregivers should obtain the correct product and dose through a healthcare professional, pharmacist or local child-health programme.

Zinc is used alongside rehydration and continued feeding, not instead of them.

Rotavirus Vaccination

Rotavirus is an important cause of severe diarrhoea in infants and young children.

Vaccination against rotavirus can substantially reduce severe rotavirus disease.

Rotavirus vaccination schedules vary between countries.

Parents should follow their country's childhood immunization programme and healthcare guidance.

How Can Infectious Diarrhoea Spread Around a Home?

Infectious diarrhoea can spread when microscopic amounts of stool or vomit contaminate:

• hands,
• toilets,
• bathroom surfaces,
• food,
• water,
• kitchen surfaces,
• or frequently touched objects.

Some viruses, particularly norovirus, spread very easily.

Good hygiene is therefore especially important when someone in the household has vomiting or diarrhoea.

Wash Your Hands Properly

Wash your hands thoroughly with soap and safe running water:

• after using the toilet,
• after changing a baby's diaper,
• after cleaning vomit or diarrhoea,
• before preparing food,
• before eating,
• and before feeding another person.

Handwashing is one of the most important ways of reducing transmission of many diarrhoeal infections.

Food Hygiene Matters

Reduce the risk of foodborne illness by:

• washing your hands before food preparation,
• keeping raw and cooked foods separate,
• cooking food thoroughly,
• keeping food at safe temperatures,
• refrigerating perishable foods appropriately,
• washing fruits and vegetables when appropriate,
• and using safe water.

Discard food that may have been contaminated by vomit or stool.

Don't Prepare Food for Others While Ill

If your diarrhoea may be infectious, avoid preparing food for other people while you are sick.

Some infections can continue to spread for a period after symptoms improve.

Local public-health recommendations vary depending on the infection and whether you work in areas such as:

• food service,
• healthcare,
• childcare,
• or schools.

Follow applicable local guidance before returning to work or food handling.

Clean Contaminated Surfaces

Promptly clean areas contaminated by stool or vomit.

Use a disinfectant appropriate for the suspected organism and follow the product's instructions regarding:

• dilution,
• contact time,
• ventilation,
• and surface compatibility.

Never mix household cleaning chemicals unless the manufacturer specifically says it is safe.

Mixing some products can release dangerous gases.

Use Safe Drinking Water

Unsafe drinking water is an important cause of diarrhoeal disease worldwide.

Use water from a safe source for:

• drinking,
• preparing food,
• making ice,
• brushing teeth,
• and preparing infant feeds.

Where the safety of water is uncertain, follow local public-health guidance regarding:

• boiling,
• filtration,
• disinfection,
• or another approved treatment method.

When Should an Adult Seek Medical Care?

Adults should seek prompt professional advice if diarrhoea is accompanied by:

• signs of dehydration,
• frequent vomiting,
• severe abdominal or rectal pain,
• high fever,
• blood or pus in the stool,
• black or tarry stools,
• six or more loose stools in a day,
• or inability to drink enough fluid.

Adults should also seek advice if diarrhoea persists for more than about two days, particularly if symptoms are not improving.

Who Should Seek Advice Earlier?

Some people have a greater risk of complications.

These include:

• babies and young children,
• older adults,
• pregnant people,
• people with weakened immune systems,
• people currently taking antibiotics,
• and people with significant underlying health conditions.

These groups may need medical advice sooner.

When Should a Child Receive Medical Attention?

Diarrhoea can become dangerous rapidly in babies and young children.

Seek prompt professional advice if a child:

• shows signs of dehydration,
• cannot drink adequately,
• repeatedly vomits,
• has blood in the stool,
• has severe abdominal pain,
• becomes unusually sleepy or difficult to wake,
• has frequent watery diarrhoea,
• or appears seriously unwell.

Newborns and young infants deserve particular caution.

Do not wait several days if an infant appears dehydrated or unwell.

When Is Diarrhoea an Emergency?

Seek urgent medical care if someone with diarrhoea develops:

• severe dehydration,
• fainting or loss of consciousness,
• confusion or markedly reduced responsiveness,
• inability to keep fluids down,
• very little or no urine,
• severe persistent abdominal pain,
• significant blood in the stool,
• signs of shock,
• or rapidly worsening illness.

Contact your local emergency medical service if the person's condition appears life-threatening.

What If Diarrhoea Lasts for Weeks?

Long-lasting diarrhoea should not simply be treated repeatedly with anti-diarrhoeal medicine.

A healthcare professional may need to investigate for:

• persistent infection,
• inflammatory bowel disease,
• coeliac disease,
• food intolerance,
• medication effects,
• malabsorption,
• irritable bowel syndrome,
• pancreatic disease,
• or other conditions.

Tests may include:

• stool testing,
• blood tests,
• and additional investigations depending on symptoms and history.

The Bottom Line

Most episodes of acute diarrhoea improve without complicated treatment.

But the most important principle is:

Do not focus only on stopping the diarrhoea—focus on preventing dehydration.

Replace lost fluids and electrolytes, use properly prepared oral rehydration solution when appropriate, continue suitable nutrition and watch carefully for warning signs.

For infectious diarrhoea, safe water, proper sanitation, handwashing and food hygiene can reduce transmission.

Remember:

Blood in the stool, severe dehydration, inability to drink, persistent vomiting, severe abdominal pain, confusion or rapidly worsening illness require prompt medical attention.

Babies and young children can become dehydrated particularly quickly.

Medical Disclaimer

This article provides general health information for an international audience and is not a substitute for diagnosis or treatment by a qualified healthcare professional. Recommendations for medicines, zinc supplementation, oral rehydration products and childhood vaccination may vary between countries. Babies, young children, older adults, pregnant people and people with chronic medical conditions may require individualized advice. Seek urgent medical care for severe dehydration, significant bleeding, inability to keep fluids down, severe pain, confusion, fainting or other potentially serious symptoms.

Sources and Further Reading

World Health Organization — Diarrhoeal Disease

https://www.who.int/news-room/fact-sheets/detail/diarrhoeal-disease

World Health Organization — Diarrhoea

https://www.who.int/health-topics/diarrhoea

World Health Organization — Zinc Supplementation in the Management of Diarrhoea

https://www.who.int/tools/elena/bbc/zinc-diarrhoea

National Institute of Diabetes and Digestive and Kidney Diseases — Diarrhea

https://www.niddk.nih.gov/health-information/digestive-diseases/diarrhea

NIDDK — Symptoms & Causes of Diarrhea

https://www.niddk.nih.gov/health-information/digestive-diseases/diarrhea/symptoms-causes

NIDDK — Treatment of Diarrhea

https://www.niddk.nih.gov/health-information/digestive-diseases/diarrhea/treatment