When your baby has a stomach bug, the first goal is to prevent dehydration. The Assurance Maladie (France's national health insurance service) recommends offering an oral rehydration solution (ORS) in very small amounts, several times an hour, and carrying on with breastfeeding or your baby's usual milk. Under 3 months, and as soon as any signs of dehydration appear, see a doctor the same day.
These pointers come from the fact sheets of the Assurance Maladie and Santé.fr, the French public health information service. They don't replace a doctor's advice, but they help you know what to do in the first few hours and when not to wait.
What is a stomach bug in babies?
Gastroenteritis is an inflammation of the digestive tract. In children, it is most often caused by a virus. The Assurance Maladie names rotavirus as the most common cause, ahead of adenovirus. Less often, a bacterium passed on through food is to blame, such as salmonella.
It mainly affects children under 2, with a peak between 6 and 12 months. Outbreaks happen in group childcare settings, nurseries and schools, especially in winter. According to the Réseau Sentinelles, a French network of GPs that monitors infections, cited by the Assurance Maladie, around 4.7 million people saw a GP for acute diarrhoea in 2013. Children under 5 accounted for 16% of these appointments.
The usual symptoms
- Runnier and more frequent stools, more than three a day.
- Vomiting, often sudden, which usually lasts one to two days.
- Cramps or tummy pain, loss of appetite.
- Sometimes a fever and great tiredness.
The diarrhoea itself can go on for one to two weeks. Most of the time, the illness clears up well. The main risk lies elsewhere: the younger the child, the faster dehydration can set in.
Stomach bug in babies: how do you rehydrate them?
Oral rehydration solution is the basic treatment. It is sold in pharmacies, in sachets to dissolve in water. Santé.fr reminds parents never to rehydrate a child with plain water. The Assurance Maladie also advises against fizzy drinks, drinks that are simply sweet and any change to the dilution on the pack.
The right way to give the solution
- At first, offer it several times an hour, in very small amounts.
- If your baby is vomiting, give it every 5 to 10 minutes, in small sips or with a spoon.
- Once the vomiting eases off, let them drink as much as they like, according to thirst.
- Keep the made-up solution in the fridge for 24 hours at most. Served cool, it often goes down better.
Milk and meals
For a breastfed baby under 2, breastfeeding carries on. If your baby drinks formula, the Assurance Maladie advises replacing it with the solution, then going back to the usual milk after 4 to 6 hours at most. The solution is then offered between bottles.
After the age of 2, children keep eating a varied diet, avoiding foods that are hard to digest. Rice, grated or stewed apple, banana, quince purée and toast are mentioned. Vegetable broths also help them drink.
Which signs of dehydration should you watch for?
A dehydrated baby doesn't complain of thirst the way an adult does. It's their behaviour and appearance that should alert you. The Assurance Maladie lists several signs that mean you should see a doctor straight away or go to A&E:
- restlessness or, on the contrary, unusual drowsiness, a baby who is hard to wake;
- fast breathing;
- a dry tongue, a pale complexion, sunken eyes with dark circles;
- weight loss of more than 5%;
- vomiting that continues despite the solution.
Weighing your baby at the start of the illness gives you a useful point of comparison. For a child weighing 8 kg, 5% is 400 g.
When should you see a doctor for a stomach bug?
For a baby under 2, the Assurance Maladie advises seeing a doctor after as few as three watery stools within a few hours. Santé.fr specifies that a baby under three months should always be seen the same day. Babies under 6 months are described as more vulnerable to dehydration.
At any age, see a doctor without delay in these situations:
- repeated vomiting with refusal to drink;
- a child who stops eating and drinking;
- diarrhoea that lasts more than two days or gets worse;
- a temperature above 38.5 °C;
- mucus or blood in the stools.
Your baby's regular check-ups are a good time to ask questions calmly, for example during an appointment at the PMI (France's mother and child health service).
Medicines to avoid without medical advice
It's tempting to want to stop the vomiting or diarrhoea. Yet the Assurance Maladie advises against several products for children:
- anti-sickness medicines;
- loperamide, not recommended under 12;
- clay-based gut coating remedies under 2, because of possible traces of lead;
- intestinal antiseptics sold over the counter;
- anti-inflammatories for a fever.
If the fever is bothering your child, paracetamol is the go-to pain reliever. The dose is worked out by weight, as explained in our article on the paracetamol dose for babies.
Limiting the spread at home and at nursery
Stomach bug viruses are very hardy. The Assurance Maladie states that they stay active for about four hours on hands, and for several days or even several weeks on objects. A child can stay contagious for a few days after they seem to have recovered.
- Wash your hands with soap after every nappy change and before preparing meals.
- Throw nappies away in a sealed bag and clean the changing mat.
- Wash soiled laundry separately, along with any toys that have been in the mouth.
- As soon as your child is able, help them learn to wash their hands.
For nursery, the rules on returning vary depending on the setting and the child's condition. Practical pointers are covered in our article on a poorly baby at nursery.
The rotavirus vaccine
Santé.fr points out that two oral vaccines, Rotarix and RotaTeq, are available against rotavirus. They are given between 6 weeks and 6 months and aim to limit severe cases. Coverage figures and the schedule are set out in our article on the rotavirus vaccine.
Key takeaways
With a stomach bug, the first thing to watch in a baby is hydration. Oral rehydration solution, given often and in small amounts, remains the key step. Breastfeeding carries on, and formula comes back quickly. Under 3 months, or at the slightest sign of dehydration, see a doctor the same day.
Sources
- Assurance Maladie, “Diarrhée et gastro-entérite de l'enfant : que faire et quand consulter ?”, ameli.fr, 23 March 2021.
- Assurance Maladie, “Symptômes et causes de la gastro-entérite chez l'enfant”, ameli.fr, 24 April 2017 (data from the Réseau Sentinelles, 2013).
- Santé.fr, “Diarrhée et gastro-entérite de l'enfant”, updated 12 August 2026.
