Diarrhoea: what should you do? Understand its causes, ways to stop it, and foods to avoid.

As Hong Kong people who enjoy eating and drinking, we have probably all experienced diarrhoea, commonly known as an upset stomach. In most cases, it is simply a temporary gastrointestinal disturbance that resolves within a few days. However, if the condition persists, dehydration occurs, or there is blood in the stool, you should be more vigilant. In fact, diarrhoea can have various causes. Understanding the common causes, symptoms and incubation periods, as well as learning the correct ways to stop diarrhoea and manage your diet, can help prevent dehydration and recurrent episodes.

The incubation period for diarrhoea varies depending on the source of infection. In general, the incubation period for bacterial infections ranges from a few hours to 5 days, while viral infections typically develop within 1 to 3 days. In most cases, the discomfort is temporary, and symptoms usually resolve naturally within a week with adequate hydration and rest.

Diarrhoea can generally be divided into two types: acute diarrhoea and chronic diarrhoea. Although their symptoms may appear similar, their causes and severity differ. Understanding the difference can help with early management and prevent the condition from being delayed.

Acute diarrhoea

Acute diarrhoea generally lasts for less than two weeks and is mostly caused by viral or bacterial infections, such as norovirus, Salmonella or Escherichia coli. When the intestines are irritated by external pathogens or affected by food poisoning, intestinal movement speeds up, meaning the water in the stools cannot be fully absorbed, resulting in watery stools.

Common symptoms include:

• Frequent bowel movements, with watery or loose stools
• Abdominal cramps, bloating or an urgent need to use the toilet
• Nausea, vomiting or a mild fever
• Dehydration in severe cases, such as a dry mouth, weakness or reduced urine output

Most cases of acute diarrhoea are mild and usually resolve on their own within 1 to 2 weeks. Patients should replenish fluids and electrolytes and keep their diet as light as possible. However, if blood appears in the stools, a high fever develops or symptoms persist for more than two weeks, medical attention should be sought as soon as possible to avoid missing the optimal time for treatment.

Chronic diarrhoea

Chronic diarrhoea refers to a condition that persists for four weeks or more, or recurs intermittently. Its causes are more complex. In addition to intestinal conditions, such as irritable bowel syndrome, it may also be related to impaired absorption, endocrine disorders or long-term medication use.

Typical symptoms may include:

• Loose or watery stools, which may contain mucus, streaks of blood or undigested food
• Abdominal pain and bloating, sometimes accompanied by a mild fever
• Weight loss, poor appetite and easy fatigability
• Malnutrition or anaemia may develop over time

If diarrhoea persists for more than four weeks, the stools contain blood or there is significant weight loss, a colonoscopy or laboratory tests should be arranged as soon as possible to identify the underlying cause and provide appropriate treatment.

Diarrhoea, or watery stools, is most commonly caused by an intestinal infection or consuming contaminated food. The following are common triggers:

• Viral infections: such as norovirus, rotavirus and sapovirus, which are the main causes of acute gastroenteritis.
• Bacterial infections: such as Salmonella and Vibrio parahaemolyticus, which are usually associated with food poisoning.
• Food-related issues: consuming spoiled food or lactose intolerance.
• Gastrointestinal conditions: conditions such as irritable bowel syndrome and inflammatory bowel disease.
• Medication side effects: particularly after taking antibiotics, which may cause an imbalance in the gut microbiota.
• Excessive artificial sweetener intake: consuming excessive amounts of sorbitol or erythritol, for example.
• Post-COVID-19 symptoms: some patients experience impaired intestinal function after infection, making them more prone to diarrhoea.

If diarrhoea is caused by a viral or bacterial infection, the pathogens can spread through contact with an infected person’s faeces or vomit, or through contaminated food and water sources. Outbreaks are more likely to occur in places with many people, such as residential care homes, schools or households. To prevent transmission, maintain good hygiene practices, such as washing your hands frequently, ensuring that tableware and kitchen utensils are clean, and avoiding sharing tableware or towels.

When diarrhoea persists or recurs, the doctor will arrange different tests based on the symptoms and physical condition to identify the cause. Not every patient needs to undergo bowel investigations; this will be determined according to the individual circumstances.

Medical Consultation and Medical History Review

The doctor will review the medical history, recent medication use, dietary habits and travel history to make an initial assessment of whether the diarrhoea is caused by an infection, food intolerance, a medication reaction or another condition. If infectious diarrhoea is suspected, the doctor will also ask whether the patient has been in contact with anyone who is ill or eaten any suspicious food.

Stool Tests

A stool sample can help the doctor determine whether there is a bacterial, viral or parasitic infection, and identify the pathogen causing the diarrhoea. It can also sometimes detect visible blood or occult bleeding in the stool.

Blood Tests or Imaging Tests

Blood tests can assess the degree of dehydration and changes in electrolyte levels, such as whether sodium or potassium levels are abnormal. If the doctor suspects other abdominal problems, such as intestinal obstruction or chronic inflammation, an abdominal ultrasound or computed tomography (CT) scan may also be arranged for further assessment.

Hydrogen Breath Test

If lactose intolerance is suspected to be causing the diarrhoea, the doctor may recommend a hydrogen breath test. The patient drinks a liquid containing lactose, after which the concentration of hydrogen in the exhaled breath is measured to determine whether the intestines are unable to break down lactose effectively.

Upper Gastrointestinal Endoscopy

This test allows the doctor to examine the stomach and upper small intestine to determine whether ulcers, inflammation or lesions are present. Tissue samples may be taken for laboratory analysis if necessary.

Flexible Sigmoidoscopy or Colonoscopy

If the diarrhoea persists or is accompanied by bloody stools or weight loss, the doctor may recommend a colonoscopy or sigmoidoscopy. This helps to check whether there is chronic inflammation, polyps or tumours in the intestines, and tissue samples (biopsies) can be taken at the same time for further analysis. However, not all cases of diarrhoea require a colonoscopy.

It is advisable to see a doctor as soon as possible if any of the following occur:

• Symptoms persist for too long: symptoms continue for more than one week
• Severe symptoms: fever, severe abdominal pain or bloody stools
• Unable to eat: severe vomiting, or unable to eat or drink water
• Signs of severe dehydration: dry mouth and tongue, or a significant reduction in urine output
• Feeling dizzy or weak High-risk groups: the patient is an older adult, young child or someone with a chronic illness
• Abnormal stools: bloody stools or stools containing pus

1. Can I drink Pocari Sweat when I have diarrhoea?


It can be consumed in moderation. Sports drinks such as Pocari Sweat contain electrolytes, which can help replenish the fluids and minerals lost through diarrhoea. However, some drinks contain high levels of sugar, so it is recommended to dilute them and drink them slowly to avoid irritating the gastrointestinal tract. If symptoms are severe or dehydration occurs, oral rehydration salts (ORS) are a more effective choice.

2. Should I take anti-diarrhoeal medication immediately when I have diarrhoea?


It is not recommended to take anti-diarrhoeal medication at the outset. Most cases of acute diarrhoea are part of the body’s natural process of eliminating pathogens, and taking anti-diarrhoeal medication too early may cause bacteria or viruses to remain in the intestines, worsening the condition. Short-term use may be considered only when diarrhoea is frequent or affects daily life, but you should first seek advice from a doctor or pharmacist.

3. How long does diarrhoea have to last before it is considered serious and requires medical attention?


Mild diarrhoea generally improves within a few days. If symptoms persist for more than 2 to 3 days, or if you experience bloody stools, a high fever, severe abdominal pain, persistent vomiting or obvious dehydration (dry mouth, reduced urination or dizziness), you should seek medical attention immediately. Older adults, young children and people with chronic illnesses should seek an examination as early as possible.

4. Can I eat century egg and lean pork congee when I have diarrhoea?


It is not recommended. Century eggs are high in fat and have a strong flavour, which may irritate the gastrointestinal tract and worsen diarrhoea. It is recommended to choose plain congee or congee water, and gradually resume a normal diet after the symptoms improve.

Recommended Foods

During a bout of diarrhoea, opt for mild, easily digestible foods to give the digestive system sufficient time to rest and recover.

• Choose low-fibre, easily digestible foods to reduce intestinal irritation.
• You may eat starchy staple foods such as plain congee, white rice, white toast, water biscuits, noodles and steamed buns.
• Choose low-fat protein foods such as fish, chicken breast, tofu or steamed egg.
• Choose tender leafy vegetables or gourds, and avoid vegetables containing coarse fibre.
• For fruit, choose peeled apples or bananas, as the pectin they contain may help relieve diarrhoea.
• Eat small, frequent meals, chew slowly and thoroughly, and cut food into small pieces to aid digestion.
• Use cooking methods such as steaming, stir-frying with a little water, blanching or stewing, and avoid deep-fried or strongly flavoured dishes.

Foods to Avoid

• Avoid milk and dairy products to prevent lactose intolerance or gastrointestinal discomfort.
• Avoid foods that are high in oil or fat, such as fried, spicy or strongly flavoured dishes.
• Avoid vegetables with coarse fibre, such as burdock, celery and vegetables with fibrous stems, to prevent irritation of the intestinal wall.
• Avoid high-fibre fruit or fruit with the skin on, such as guava, unpeeled apples or grapes.
• Avoid raw or chilled foods, such as raw vegetable salads, soft-boiled eggs or cold drinks.
• Avoid drinks or ice cubes from unknown sources to prevent consuming contaminated water.

Dietary Tips

During a bout of diarrhoea, the body can lose water easily. Therefore, take small sips of water regularly. You may choose plain water or electrolyte drinks to help maintain the body's fluid balance and prevent dehydration. As the digestive system gradually settles, start with starchy foods such as plain congee and white rice, then add low-fat proteins such as fish and tofu, and finally gradually increase your intake of vegetables and fruit to replenish nutrients. In general, choose light foods and eat small, frequent meals. Do not eat too much at any one time, and avoid greasy, spicy or strongly flavoured foods to reduce the burden on digestion.

Ordinary diarrhoea usually improves within a short period. The following are several common ways to relieve and treat it, which can help the digestive system gradually return to normal.

Acupressure

Traditional Chinese medicine practitioners believe that gently massaging specific acupoints may help regulate digestive function. You can gently press the “Tianshu” acupoint (approximately three finger widths on either side of the navel) and “Zusanli” (approximately four finger widths below the outer side of the knee), applying gentle clockwise pressure for 1 to 2 minutes. This may help promote intestinal movement and relieve abdominal pain and bloating. However, this is a complementary therapy that can be used alongside medication or dietary adjustments. If you experience severe abdominal pain or a high fever, seek medical attention immediately to avoid delaying treatment.

Antidiarrhoeal medication

Common antidiarrhoeal medicines such as Loperamide can temporarily slow intestinal movement and reduce the frequency of bowel movements, making them suitable for managing mild diarrhoea. However, they are not recommended if diarrhoea is accompanied by a high fever, bloody stools or a bacterial infection, as the medicine may cause pathogens to remain in the body and worsen the condition. It is best to consult a doctor or pharmacist before taking them, and they should not be taken long term without medical advice.

Antibiotics or antiparasitic medication

If diarrhoea is caused by a bacterial or parasitic infection, a doctor will prescribe the appropriate medication based on the results of stool tests. However, antibiotics are ineffective against viral diarrhoea, such as norovirus, and recovery depends on the body’s immune system. Do not purchase medication without medical advice, as this may lead to antibiotic resistance or an imbalance in the gut microbiota.

Fluid replacement therapy (intravenous fluids or oral electrolyte solutions)

If severe dehydration or persistent vomiting occurs, a doctor may recommend intravenous fluids or oral electrolyte solutions to replenish fluids and minerals and help stabilise bodily functions.

Probiotics

Probiotics may help balance the gut microbiota and shorten the duration of diarrhoea. They are particularly suitable for people who have taken antibiotics or have a weaker digestive system. They can be taken in the form of capsules, powders or probiotic drinks, but low-lactose or dairy-free products should be chosen to avoid further irritating the intestines.

Maintain a bland diet

During an episode of diarrhoea, you should allow your intestines to “rest”. It is recommended to eat bland, low-fat and easily digestible foods, such as congee, noodles, steamed fish or tofu, and to avoid spicy, fried and strongly flavoured foods to reduce the burden on the digestive system.

Replenish fluids and electrolytes

Diarrhoea can cause the body to lose large amounts of fluids and electrolytes, such as sodium and potassium, which can easily lead to dehydration. In mild cases, you can replenish fluids by drinking oral rehydration salts (ORS), clear soup or diluted fruit juice.

Although diarrhoea is usually a temporary discomfort, if it recurs or requires further examinations (such as colonoscopy, CT, MRI, etc.), the medical costs can often be considerable. Taking out suitable medical insurance early can not only ease the financial burden, but also enable you to receive treatment promptly when needed.

Under the Voluntary Health Insurance Scheme, CT, PET and MRI examinations are categorised as “specified diagnostic imaging tests”. As long as there is a written recommendation from the attending doctor, they are eligible for reimbursement whether carried out during hospitalisation, at a clinic or in a day surgery centre.

There is a wide range of medical insurance products on the market, each with different coverage terms. If you would like to understand more clearly which product best suits your personal needs, or need assistance interpreting the policy terms, please feel free to consult 10Life’s licensed insurance advisers for professional advice.

Further reading
【MRI Price Comparison 2025】A comprehensive guide to MRI scan costs and contrast agent side effects
【Voluntary Health Insurance Scheme】How should you choose between a standard ward and a semi-private room plan? (Including a comparison of premiums from 7 insurance companies)
【Which Voluntary Health Insurance Scheme is best in 2025】Comparison of “5-star” plans: which one is the choice for middle-class families?
 

Last updated: 17 November 2025

This English version of this article has been generated by machine translation powered by AI. It is provided solely for reference purposes. In the event of any discrepancy or inconsistency between this translation and the original Chinese version, the Chinese version shall prevail.