Vomiting is one of the most common reasons parents call a health professional in the first three years. Most of it is a stomach bug that runs its course in a couple of days. The harder bit is knowing the small set of patterns that mean stop reading and pick up the phone — and the smaller set that mean go straight to A&E. For a comprehensive overview, see our complete guide to child health.
What's Usually Going On
Two patterns make up most of what parents call about:
Posseting in babies. Small mouthfuls of milk brought up calmly after feeds, usually in the first six months, no distress, weight gain on track. That's reflux, not vomiting. A muslin and a bit of patience.
Viral gastroenteritis. Sudden-onset vomiting, often joined by diarrhoea a few hours later, sometimes a low fever, sometimes off food. It tends to start dramatically — repeated retching for a few hours — then settle, and the diarrhoea is usually what hangs around longest. One to three days is the typical course in a previously well child. Most of it can be managed from the sofa.
Same-Day GP or NHS 111
The signs that mean don't wait until tomorrow:
Dehydration. This is the single most important thing to read. The signs to watch in this order:
- Wet nappies dropping off. Fewer than usual in the last 6–8 hours, or a nappy that's been on for hours and is barely damp.
- Dry mouth and no tears when they cry.
- Sunken fontanelle in babies whose soft spot is normally flat or slightly raised.
- Sleepier or floppier than usual. Hard to engage, eyes that look dull, less wriggly than baseline.
- Mottled or pale skin, cool hands and feet.
Dehydration moves much faster in babies than in older children. A toddler can compensate for a day; a four-month-old cannot.
Other red flags for same-day:
- Vomiting going past 24 hours in a baby under one year
- No urine produced for more than eight hours
- Pain that's getting worse, or pain that's continuous rather than coming in waves (gastro cramps come and go; constant severe pain points elsewhere)
- A child who's getting more lethargic rather than less
- Vomiting in a child with diabetes, or any chronic illness that complicates fluid balance
When to Go Straight to A&E or Call 999
A short list, all worth knowing in advance:
Bile-stained (green) vomit. Bright green or yellow-green vomit in any baby or young child is treated as a surgical emergency until proven otherwise. It points at obstruction below the level of the bile duct — most concerning is volvulus (a twist of the gut), where minutes-to-hours matters. Don't wait, don't try food, don't ring the GP — go to A&E.
Blood in vomit. Either fresh red, or "coffee grounds" (older, partially digested). A few streaks after a particularly forceful vomit may be a tear in the oesophagus that resolves on its own, but you can't tell without an assessment.
Projectile vomiting in a 2–8-week-old. Vomit that genuinely shoots — across the room, not just runs — after every feed, in a baby in this age window, points at pyloric stenosis. The classic giveaway is that the baby is ravenously hungry again immediately after vomiting, because the milk never got past the stomach. Treatment is a small operation (pyloromyotomy) with an excellent outcome, but the baby needs assessing within hours, not days.
Any vomiting in a baby under two months. Newborn vomiting is treated more cautiously because sepsis, meningitis, and surgical causes all sit higher on the list of possibilities. Get them seen.
Distended, hard, or tender abdomen. Combined with vomiting, suggests obstruction or perforation.
Signs of meningitis. Vomiting alongside any of: a non-blanching rash (does not fade under pressure with a glass), neck stiffness, dislike of light, a high-pitched or unusual cry, drowsiness, a bulging fontanelle. Call 999.
Head injury followed by vomiting. Particularly if the vomiting starts later, or repeats more than once or twice.
Looking After Them at Home
For straightforward gastroenteritis:
- Little and often. Once the worst of the retching settles, offer 5–10 ml of fluid every five minutes for a small child — a syringe or a teaspoon works well. Pushing a full cup will come straight back up. Build the volumes up over an hour or two.
- Don't stop milk. Breastfed babies should continue to breastfeed; formula-fed babies should continue formula. NICE specifically advises against switching milks during gastroenteritis.
- Oral rehydration solution (ORS — Dioralyte, Electrolade) is the right fluid in older babies and toddlers if vomiting is significant. It replaces salts and sugars in the right ratio for absorption. Sip it cool, slowly.
- Skip fruit juice, squash, and sports drinks. They're too sugary and can pull water into the gut, making diarrhoea worse.
- Food, when they want it. Once vomiting has settled for a few hours, offer whatever they'll eat. The old "BRAT" diet (banana, rice, apple, toast) isn't necessary — current advice is normal food as tolerated. Plain, bland things often go down easier in the first day.
- Anti-sickness medication (ondansetron) is occasionally prescribed for older children with severe vomiting where home rehydration is failing. It's a GP or A&E decision, not over the counter.
Tracking the Wet Nappies
The single most useful thing to keep an eye on is urine output. Count nappies, note the times, and you'll know within a few hours whether things are getting better, holding steady, or sliding. Most vomiting episodes never reach the point of needing assessment — but the families who get caught out are usually the ones who didn't notice the gap between wet nappies stretching from three hours to seven. Healthbooq makes that easier; a notes app or a piece of paper on the fridge does the job too.
If you're not sure, NHS 111 is built for the call where you're not sure. They are not annoyed when it turns out to be nothing.
Key Takeaways
Most vomiting in toddlers is viral gastroenteritis and clears in one to three days with little-and-often fluids. Same-day GP review for: dehydration (fewer wet nappies, dry mouth, drowsy, mottled), vomiting past 24 hours in a baby under one, no urine for over eight hours, or pain that's getting worse rather than going off in waves. Urgent / 999 review for: green-stained (bile) vomit at any age, blood in vomit, projectile vomiting in a 2–8-week-old, vomiting in a baby under two months, distended hard abdomen, or vomiting with non-blanching rash, neck stiffness, photophobia, or a bulging fontanelle. Don't stop milk for breastfed or bottle-fed babies; oral rehydration solution is the fluid of choice in older infants and toddlers; no fruit juice or sugary drinks.
