Gastroenteritis in children

by | Kids and Teens Health

Gastroenteritis – often simply called ‘gastro’ in Australia – is very common among young children. Gastroenteritis means inflammation of the stomach and bowel, and results in vomiting and/or diarrhoea. In children, gastroenteritis is usually caused by an infection – most often with a virus, but it can also be caused by bacteria or parasites.

Most children recover from gastroenteritis in a few days. Keeping your child hydrated by encouraging them to drink frequently is important, as dehydration can be serious.

What are the symptoms of gastroenteritis?

Gastroenteritis often comes on suddenly with nausea (feeling sick in the stomach), vomiting and/or diarrhoea (more frequent, loose or watery bowel movements). Children may also have a fever, reduced appetite and abdominal pains.

Symptoms usually last from 24 hours to a week, depending on the cause of the gastroenteritis. Sometimes diarrhoea may persist for slightly longer. Gastroenteritis caused by an infection with a parasite can cause longer-lasting diarrhoea that comes and goes, as well as tiredness and weight loss.

Gastroenteritis and dehydration

The major concern in children with gastroenteritis is that they may become dehydrated (dry and lacking water) because of fluid loss through vomiting and diarrhoea. Babies and young children are particularly prone to dehydration.

The main symptoms of dehydration are being thirsty and not passing very much urine (in babies, having fewer wet nappies than usual). Other signs of dehydration may include a dry mouth and skin and feeling faint or light-headed. Signs of more severe dehydration include drowsiness, rapid or deep breathing, and cold hands or feet. Dehydration can be serious, so if you think your child may be dehydrated, take them to see your doctor as soon as possible or take your child to emergency.


Gastroenteritis in children is usually caused by an infection. Sometimes a reaction to a new food or medicine can cause gastroenteritis in children.

Infectious gastroenteritis

Most cases of gastroenteritis in children are caused by viruses. Viruses are often very contagious and spread easily from person to person. They sometimes cause outbreaks of gastroenteritis in places such as childcare centres and schools, where children are in close contact with each other. Viral gastroenteritis usually lasts one to 3 days.

Viruses that commonly cause gastroenteritis in children include the following.

  • Norovirus is the most common cause of gastroenteritis in older children. It is sometimes called the winter vomiting bug or virus even though it’s possible to be infected at any time of year. Norovirus causes sudden severe vomiting and is highly contagious.
  • Rotavirus was the most common cause of severe viral gastroenteritis in young children before routine vaccination was introduced. Severe infection is now less much less common in Australia.
  • Adenovirus usually affects babies and young children, causing fever, vomiting and diarrhoea.
  • Astrovirus usually causes diarrhoea (vomiting is uncommon).

Bacteria that commonly cause gastroenteritis include E. coli, Salmonella or Campylobacter. Bacterial gastroenteritis is usually caught by eating contaminated foods or water. When you get gastroenteritis from food it may be called food poisoning. Some bacteria produce toxins that can cause severe food poisoning, resulting in stomach cramps and vomiting a few hours after eating.

Bacterial gastroenteritis can also sometimes develop during or after taking a course of antibiotics, often due to infection with the bacterium Clostridium difficile. This type of gastroenteritis is relatively uncommon but can be serious.

Gastroenteritis can also be caused by parasites such as Giardia and Cryptosporidium, usually via contaminated water or close contact with others.

Another way you can catch gastroenteritis is though swimming or playing in contaminated water, such as at a water park, swimming pool, lagoon or river. Public swimming pools and water parks should be frequently tested and carefully monitored for bacteria. Always check for signs around lagoons or rivers to make sure they are not polluted and are safe for swimming.


Your doctor will ask about your child’s symptoms and how long they have been sick. They may also want to know whether other family members or people you’ve recently been in contact with have been unwell. Let your doctor know if your child has recently travelled overseas or taken any medicines.

When examining your child, your doctor will look for signs of dehydration. In most children with mild gastroenteritis no tests are needed. The diagnosis can usually be made based on their symptoms and physical examination.

Testing may be recommended if your child has any unusual symptoms, symptoms that have lasted more than a few days, or if they have recently travelled overseas. Your doctor may ask you to collect (or help your child to collect) a stool sample (poo sample). The sample will be sent to a microbiology laboratory to help work out the type of germ that has caused the gastroenteritis. Occasionally blood tests may also be recommended.

Children who have severe gastroenteritis or who are dehydrated may need further tests and treatment in hospital – your doctor may recommend you go straight to emergency for immediate treatment.


Children with mild gastroenteritis can usually be cared for at home with rest and adequate fluids to prevent dehydration. Encourage your child to rest as much as possible while recovering. Children with more severe symptoms and babies are at risk of severe dehydration – they need to be monitored closely and may need treatment with fluids and medicines in hospital.


The main treatment for gastroenteritis is to keep your child well hydrated by encouraging them to drink plenty of fluids. If they are vomiting or feeling sick, drinking small amounts of fluid frequently is often the best approach. Babies and children should be offered a drink after each time they vomit.

Suitable fluids may include the following.

  • Breast milk for babies who are being breast fed.
  • Oral rehydration solutions, which are available from the chemist (e.g. Gastrolyte, Repalyte, Hydralyte). Oral rehydration solutions are available as ready-made solutions, ice blocks or jelly-ice blocks or can be made up with water from powder sachets or effervescent tablets.
  • Clear fluids such as fruit juice or flat lemonade that has been diluted appropriately (for example, 20 mL of apple juice mixed with 80 mL of water) or diluted cordial (for example, 100 mL of water added to 5 mL of cordial concentrate). Clear fluids are suitable only if your child is not dehydrated, otherwise oral rehydration solutions are a better option. Clear fluids should be made up with cooled, boiled water for babies younger than 12 months.

Your doctor can advise as to the type of fluid and how much to give in your child’s case.

Babies who are exclusively breast fed should continue to be breast fed and should be offered smaller amounts of breast milk more frequently than usual. In addition to breast milk, oral rehydration solution (ORS) or cooled, boiled water can be given in a bottle. Make sure you get advice from your doctor or pharmacist about how to make up the oral rehydration solution and how much to give.

Bottle-fed babies should be given ORS or clear fluids instead of formula for the first 12 hours while they are vomiting. Using a slow teat on the bottle can help stop your baby drinking too quickly, which can help them keep the fluids down. Aim to get them back to formula feeds (formula does not need to be diluted) within 12-24 hours. Give them smaller feeds more frequently. Drinks of ORS can also be offered. See your doctor if they are not back on formula within 24 hours.

Children with more severe gastroenteritis may need to be admitted to hospital to be given fluids via a nasogastric tube (a tube through the nose into the stomach) or intravenous fluids (through a drip into a vein).


Children may be offered easily digested foods when they feel like eating. In general, it’s best to resume eating within 24 hours. It’s a good idea to start them with small amounts of food at first. Suitable foods include toast, plain crackers, jelly, bananas and rice.

Some children may have difficulty digesting dairy products, such as cow’s milk, cheese or yoghurt, for days or weeks after a bout of gastro due to temporary lactose intolerance. Lactose-free foods and formula may be recommended for a few weeks.


In some cases doctors may prescribe medicine to relieve severe vomiting. This is generally only done when children are being treated in hospital. Ondansetron is a medicine that can be used to relieve vomiting in children and help prevent dehydration. It is available in a wafer that dissolves in the mouth, making it easier to take.

Medicines to stop diarrhoea (such as Imodium) are NOT recommended for children, as they are not helpful and may be harmful.

In some cases, babies or children with bacterial or parasitic gastroenteritis may be treated with antibiotics to reduce the length and severity of the illness or to prevent complications.

What not to do when your child has gastroenteritis

Don’t give sports drinks, energy drinks or soft drinks. Don’t give your child undiluted cordial, lemonade or fruit juice – there is too much sugar in these drinks when not diluted with water, which can make your child’s diarrhoea worse.

Don’t give fatty or rich foods while your child is sick or when they are recovering.

Don’t send your child to school or daycare until they have been completely clear of symptoms for at least 24-48 hours.

When to see a doctor

See a doctor if your child’s symptoms last for more than one to 2 days. If you think your child may be dehydrated you need to see a doctor straightaway. The risk of your child becoming dehydrated is generally higher the younger they are. Babies with gastroenteritis should be closely watched, and need to see a doctor sooner. In particular, babies younger than 6 months of age can become dehydrated very quickly.

If your child has mucus or blood in their stool, you should also take them to the doctor as soon as possible. This may indicate a bacterial cause for the gastroenteritis.

If you are worried about a persistent tummy ache or fever in your child, you should also seek medical care.


Infectious gastroenteritis can be easily passed on, so children with gastroenteritis should not go to school or childcare, or mix with other children. To avoid spreading the infection to others, it’s also advised that children with diarrhoea do not go swimming in public swimming areas. Wait 24-48 hours from the last episode of vomiting or diarrhoea until resuming usual activities.

One of the most important things you can do to stop the spread of infection is to wash your hands. Washing thoroughly with soap and running water for at least 10-20 seconds, especially before food preparation and after changing nappies, helps prevent spread of infection. Anyone who has been sick with gastro should avoid preparing food for others until they have been clear of symptoms for about 2 days. Keeping food at the correct temperature and taking care with food preparation and storage helps prevent gastroenteritis due to food poisoning.

Clean and disinfect any surfaces or objects that have been vomited on straight away. Also, wash any clothes or bedding that have been soiled as soon as possible, using a long wash cycle, and dry in the sun or a clothes dryer. Regularly clean other hard surfaces, such as taps, benches and doorknobs, as well.

A vaccine against rotavirus is available and given in Australia as one of the routine childhood immunisations, at 2 months, 4 months and sometimes also 6 months of age. This vaccine has been very effective in reducing the number of infants and young children developing severe gastroenteritis due to rotavirus infection.