Vomiting in children: rehydrating properly, and the signs that mean get help
Last updated September 3, 2026.
A vomiting child is usually a stomach bug doing its worst for a day or two, and your one real job is preventing dehydration: small sips, very often. The instinct to give big drinks to replace what is lost backfires, because a full stomach triggers the next vomit. Slow, steady, relentless is the method that works.
What is usually going on?
In children, sudden vomiting is most often viral gastroenteritis, frequently with diarrhea and mild fever following. Food poisoning, coughs that trigger retching, travel sickness, and eating too much too fast account for many others. It typically settles within 24 to 48 hours. Babies posset (small milky possets after feeds), which is normal and not vomiting; vomiting is forceful and larger. The patterns that mean something else: green (bile-stained) vomit, blood, severe or worsening tummy pain, vomiting after a head injury, or projectile vomiting in a very young baby.
What actually helps?
- Oral rehydration solution in tiny, frequent amounts: pharmacy ORS sachets mixed exactly to the packet instructions, given as a few teaspoons every 5 to 10 minutes. If that stays down for an hour or two, gradually increase the amount. This replaces water and the salts plain water misses.
- Keep breast or formula feeds going: do not stop feeding babies; offer smaller feeds more often, plus ORS between them. Breast milk is the best fluid for a vomiting baby.
- Food when they ask, plain first: once vomiting settles, offer normal foods as appetite returns; there is no need to starve a bug, and early refeeding helps the gut recover. Start plain (toast, rice, banana) if that is all they fancy.
- What to avoid: no fizzy drinks, fruit juice, or sports drinks as the main fluid (the sugar load worsens vomiting and diarrhea; ORS is different because of its exact balance), no anti-vomiting medicines without medical advice, and no forcing large drinks.
- Contain it at home: gastroenteritis spreads through households fast: scrupulous handwashing, a separate towel for the child, cleaning vomit promptly with hot water and detergent, and keeping them off school or nursery until 48 hours after the last vomit or loose stool.
When is it an emergency?
Dehydration is the danger, so know its signs: far fewer wet nappies or trips to the toilet (roughly half normal), no tears when crying, a dry mouth, sunken eyes (or a sunken soft spot in a baby), and unusual drowsiness or floppiness. Those need same-day care. Call 999 (or 911/112) or go to the emergency department for: green bile-stained vomit, blood in vomit, severe or constant tummy pain, a swollen or tender tummy, a non-blanching rash, a stiff neck, vomiting after a head injury, or projectile vomiting in a baby under about 12 weeks. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
How do I rehydrate a vomiting child?
With oral rehydration solution (ORS) in small, relentless sips: a few teaspoons every 5 to 10 minutes, using pharmacy sachets mixed exactly to the instructions. Big drinks trigger vomiting; tiny frequent amounts absorb. Once sips stay down for an hour or two, increase the amount gradually. ORS beats water for stomach bugs because it replaces the salts lost in vomit and diarrhea. If even sips will not stay down after a few hours of trying, that is the threshold for being seen.
How long does a vomiting bug last in children?
The vomiting phase of viral gastroenteritis typically lasts 24 to 48 hours, with diarrhea often following and trailing on for several days. Energy and appetite lag a few days behind. Vomiting persisting beyond 2 days, or a child who is not clearly improving by then, deserves a medical look, as does vomiting that is the main feature for more than a day in a baby under 1 year.
When can my child eat normally again?
As soon as they want to. The old starvation approach is outdated: once vomiting settles, offer normal food as appetite returns, starting with plain options if that is what they fancy. Early refeeding actually helps the gut lining recover. Milk feeds for babies should not be stopped; breast milk especially continues through the illness. The only pause is during active vomiting itself, when fluids in sips take priority.
My baby is projectile vomiting. Is that the same thing?
No, and the age matters. Posseting, small milky dribbles after feeds, is normal baby behavior. Forceful vomiting after most feeds in a baby roughly 3 to 6 weeks old, with a baby who stays hungry and starts losing weight, is the classic picture of pyloric stenosis, a narrowing of the stomach outlet that needs same-day assessment and a small operation. In older babies and children, forceful vomiting with a bug is common and follows the usual rules, but green bile-stained vomit at any age is always urgent.
When should I take my vomiting child to the doctor?
Same-day for: signs of dehydration (wet nappies or toilet trips under half normal, no tears, dry mouth, sunken eyes or fontanelle, drowsiness), vomiting that will not let even sips stay down, green or bloody vomit, severe or worsening tummy pain, a swollen or tender tummy, a non-blanching rash, a stiff neck, vomiting after a head injury, or a baby under 1 year vomiting for more than a day. Trust your read on your own child; a parent saying this is not normal for them carries real weight.
How do I stop the bug spreading through the house?
Handwashing with soap and water after the toilet, after cleaning up vomit, and before food, noting that alcohol gels do not kill norovirus, the usual culprit. Give the child their own towel, clean vomit promptly with hot water and detergent then disinfect, and wash soiled clothing and bedding hot. Keep the child off school or nursery until 48 hours after the last vomit or loose stool, and do not prepare food for others while you are ill or in that 48-hour window.
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