A stomach bug in babies can begin abruptly: a normal feed, then vomiting or an unusually watery nappy. Most cases improve with time, but babies can lose fluid faster than older children. The first priority is not stopping every loose stool. It is keeping your baby hydrated while recognising when symptoms need medical attention.
Viral gastroenteritis is a common cause of a baby stomach virus. You may also hear it called an infant stomach bug. The practical questions are the same: what counts as illness, which fluids help, and which changes should never be watched at home?
What does a stomach bug look like in a baby?
Typical symptoms include sudden vomiting, diarrhoea, reduced appetite, fussiness and sometimes a mild fever. Vomiting may arrive before loose stools. Some babies seem tired or uncomfortable between episodes but remain alert and respond normally when comforted.
Diarrhoea means a noticeable change from your baby’s usual pattern, not simply one soft nappy. Breastfed babies often have naturally loose, seedy stools. A sudden increase in watery nappies, especially alongside vomiting, is more suggestive of gastroenteritis.
Viruses such as norovirus and rotavirus can cause these symptoms. Bacterial infections and conditions unrelated to infection can look similar, however, so do not assume every vomiting baby has a harmless virus. Your baby’s age, temperature and behaviour matter as much as the number of nappies.
Why hydration matters more than appetite
With a stomach bug in babies, vomiting and watery diarrhoea remove both water and important salts. Infants, especially those under six months, have smaller fluid reserves and are more vulnerable to dehydration. A baby who misses several feeds while continuing to lose fluid deserves prompt medical advice.
Keep breast milk or formula going
Continue breastfeeding, offering shorter, more frequent feeds if your baby seems nauseated. If formula-fed, continue the usual formula prepared at its normal strength; never dilute it to replace lost fluid. If your baby vomits after a feed, give the stomach a brief chance to settle, then try a smaller amount more frequently.
For a baby already eating solids, milk feeds remain especially important during illness. Once they are interested and adequately hydrated, offer familiar foods without forcing a meal. A day of lighter eating is usually less concerning than declining fluid intake.
When an oral rehydration solution helps
An oral rehydration solution, or ORS, contains balanced water, salts and glucose. A healthcare professional may recommend it when diarrhoea is frequent, vomiting makes feeding difficult or dehydration is beginning. Follow age-appropriate instructions and mix a commercial product exactly as directed. Do not substitute juice, fizzy drinks, sports drinks or homemade salt mixtures.
Small, repeated amounts can be easier to keep down than a large drink. If your baby refuses fluids or vomits every attempt, seek urgent medical assessment rather than repeatedly trying at home. Babies under six months should receive professional advice early about significant vomiting or diarrhoea and how to use ORS.
How to spot dehydration before it becomes severe
Look at trends over several hours, not just one nappy. Warning signs include noticeably fewer wet nappies than usual, dark urine, a dry mouth, fewer tears when crying, sunken eyes or a sunken soft spot on the head. Unusual sleepiness, irritability or cool hands and feet add concern.
Imagine your baby normally has regular wet nappies but has produced none for around eight hours after repeated watery stools. Even if they briefly smile or seem settled, that lack of urine warrants urgent medical advice. Do not wait for every dehydration sign to appear.
A record of feeds, vomiting episodes, watery nappies and wet nappies makes conversations with a clinician clearer. For more detail, a guide to signs of dehydration in babies is a useful companion to this checklist.
Red flags: when to get medical help
Seek emergency care now
Call emergency services or go to an emergency department if your baby is difficult to wake, unresponsive, struggling to breathe, has a seizure, appears severely weak or shows signs of shock such as pale, mottled skin and very cold extremities. Green vomit, blood in vomit, a markedly swollen abdomen or severe persistent abdominal pain also needs immediate assessment.
Contact a clinician urgently
Get prompt medical advice for blood in the stool, repeated vomiting that prevents feeds, suspected dehydration, or a baby who is getting worse rather than better. A temperature of 38°C (100.4°F) or higher in a baby younger than three months needs urgent medical assessment, even if a stomach bug seems likely. Very young babies with diarrhoea should also be assessed promptly.
If you are worried about an infant under 12 months, particularly under six months, contact a healthcare professional early. A separate guide to fever in babies explains why age changes the urgency.
Making the next 24 hours more manageable
Keep your baby comfortable, change soiled nappies promptly and gently clean and dry the skin to reduce irritation. Offer feeds frequently, allow rest and avoid overheating. Do not give over-the-counter anti-diarrhoea or anti-vomiting medicine to a baby unless a clinician specifically prescribes it. Antibiotics do not treat viral gastroenteritis.
Vomiting from gastroenteritis often settles within one to three days, while diarrhoea can last around five to seven days and sometimes longer. Persistent symptoms, renewed fever or a baby who seems increasingly unwell deserve reassessment rather than assuming the virus is running its course.
Wash hands with soap and water after changing nappies and before preparing feeds. Clean contaminated surfaces and wash soiled clothing. Hand sanitiser alone is less dependable against norovirus. Follow your childcare provider’s illness policy; many settings require a child to be free of vomiting and diarrhoea for at least 48 hours before returning.
Frequently asked questions
Can a baby have a stomach bug without diarrhoea?
Yes. Vomiting can appear first, and some infections cause mainly vomiting. But vomiting without diarrhoea can have other causes, so seek advice for persistent episodes, green vomit, pain or a baby who seems unwell.
Should I stop formula during a stomach bug?
No. Continue normal-strength formula unless a healthcare professional gives different instructions. Smaller, more frequent feeds may be easier after vomiting. Never water down the formula.
How long does a baby stomach virus usually last?
Vomiting commonly improves within a couple of days. Loose stools may continue for a week and occasionally up to two weeks. Duration alone is not a reason to ignore dehydration, blood in stool or worsening behaviour.
Is it safe to give a baby plain water for diarrhoea?
For young infants, breast milk or correctly prepared formula should remain the main fluid. Plain water is not a replacement for lost salts, and too much can be unsafe. Ask a clinician whether ORS is appropriate for your baby’s age and symptoms.
Helping your baby recover safely
Most babies recover from viral gastroenteritis with supportive care, but the safest plan follows your baby’s hydration and behaviour rather than a fixed timetable. Keep usual milk feeds going, note wet nappies and act promptly on warning signs. When something feels noticeably different from your baby’s normal behaviour, ask for medical advice. A guide to caring for a sick baby at home can help with everyday comfort while recovery continues.
