What is diarrhoea?
Diarrhoea is the passing of loose, watery stools more frequently than normal. It is a very common problem that almost everyone experiences from time to time, and is usually short-lived. Acute diarrhoea lasts a few days and is typically caused by an infection, while diarrhoea lasting longer than a few weeks (chronic) is less common and more likely to have an underlying cause worth investigating.
In most cases, diarrhoea is the body's way of clearing an infection or irritant from the gut, and it settles on its own. The main concern, particularly in young children, older adults and those who are unwell, is dehydration from the loss of fluids, which is why replacing fluids is the key part of looking after yourself or others with diarrhoea.
Common causes
Diarrhoea has many possible causes, most of them temporary. Common causes include:
- •Viral infections, such as norovirus or rotavirus
- •Bacterial infections, often from contaminated food or water (food poisoning)
- •A reaction to medication, such as some antibiotics
- •Anxiety or stress, in some people
- •Food intolerances
- •Longer-lasting conditions, such as irritable bowel syndrome or inflammatory bowel disease, for chronic diarrhoea
Treatment and staying hydrated
Most diarrhoea clears up on its own without specific treatment, and the most important thing is to stay hydrated by drinking plenty of fluids in small, frequent sips. For most adults, water is suitable, and oral rehydration sachets from a pharmacy can help replace lost salts and fluids, which is especially useful for those at higher risk of dehydration.
Eating can usually continue when you feel able, starting with small, plain meals. Anti-diarrhoeal medicines are available from pharmacies and can reduce symptoms in adults for short-term relief, though they are not suitable for everyone or in all situations, so a pharmacist can advise. Most importantly, watch for signs of dehydration and seek help if they appear, particularly in young children and older adults.
Preventing diarrhoea
Since diarrhoea is often caused by infections spread through contaminated food, water or contact, good hygiene is the main way to reduce the risk. Washing your hands thoroughly with soap and water, especially after using the toilet and before preparing or eating food, is one of the most effective measures. This is particularly important when someone in the household has diarrhoea, as infections like norovirus spread easily.
Food and water safety also help: storing, preparing and cooking food properly, and being cautious with food and water when travelling in areas where standards may differ. If you have diarrhoea from an infection, staying off work or school until you have been free of symptoms for a couple of days helps avoid passing it on. These simple steps significantly reduce the spread of the infections that most often cause diarrhoea.
Diarrhoea in babies and children
Diarrhoea is common in babies and children, often from viral infections, and usually clears up within a few days. However, children — especially babies — can become dehydrated more quickly than adults, so keeping them hydrated is the main priority and a reason to be more watchful than with adults.
Encourage a child with diarrhoea to drink fluids regularly. For breastfed babies, continuing breastfeeding is recommended, and oral rehydration solutions may be advised for replacing fluids and salts, particularly if there is a risk of dehydration. A pharmacist or doctor can advise on the right approach for a child's age.
Seek medical advice early for a baby or young child with diarrhoea, particularly if they show signs of dehydration (such as fewer wet nappies, dryness, drowsiness or sunken features), have blood in their stools, are vomiting persistently, have a high fever, or seem unwell. Because young children can deteriorate quickly, it is always better to seek advice sooner rather than later.
When diarrhoea becomes long-lasting
Most diarrhoea is acute, lasting only a few days. When diarrhoea persists for weeks, or keeps coming back, it is considered chronic and is more likely to have an underlying cause that benefits from investigation. This is different from the short-lived infections that cause most cases, and warrants a conversation with a doctor.
Causes of longer-lasting diarrhoea include conditions such as irritable bowel syndrome (IBS), inflammatory bowel disease, food intolerances like lactose intolerance, and reactions to medications. Some of these are managed with dietary changes, others with specific treatment, so identifying the cause is the key step. A doctor can arrange any tests needed and guide treatment.
If your diarrhoea has lasted more than a couple of weeks, keeps returning, or comes with other symptoms such as unexplained weight loss, blood in the stools, or persistent tummy pain, it is worth seeing a doctor. While many causes of chronic diarrhoea are manageable, getting to the cause allows the right treatment and rules out anything that needs closer attention.