Diarrhoea and Vomiting in Children: When to Worry

In short: most diarrhoea and vomiting in children is caused by a virus, and it gets better on its own within a few days to a week. The one thing that turns it dangerous is dehydration. Keep small amounts of fluid going, watch for dry nappies, sunken eyes, unusual sleepiness or no tears, and go to a doctor straight away if your child cannot keep any fluid down, has green or blood-stained vomit, blood in the stool, or seems floppy and hard to wake.

It usually starts the same way. A child is fine at dinner, then wakes at 2am and vomits over everything, and by morning the diarrhoea has started too. As a paediatrician in Kuala Lumpur, I see this every single week, and in most cases the WhatsApp panic is worse than the illness itself.

Here is what I want every parent to hold onto: with a simple tummy bug, the diarrhoea and vomiting are usually not the emergency by themselves. They are the body clearing the infection. The emergency, when there is one, is dehydration, and there is a short list of other warning signs below. So that is what we watch.

What is gastroenteritis, and why does the danger come from dehydration?

Gastroenteritis is an infection of the gut. In children it is usually viral, most often rotavirus or norovirus, and it spreads easily through nurseries, tadika, and family homes. It can also come from food or water that is not clean, which matters in our climate.

The vomiting and diarrhoea are the symptoms everyone notices. But a small child has very little spare fluid in their body, and they can lose it fast through watery stools and vomit. Younger children lose it fastest. That is why a baby with a stomach bug needs closer watching than an older child with the same bug.

So the whole job at home is simple to say and harder to do at 3am: replace the fluid faster than they are losing it, and watch for the signs that they are falling behind.

How long does diarrhoea and vomiting usually last?

For most children, the shape of it is predictable.

• Vomiting usually settles within one to two days, and almost always within three.

• Diarrhoea usually lasts five to seven days, and settles within two weeks.

This is the pattern described by the UK's NICE guidance, and it matches what I see in clinic. If the vomiting is still going strong after two days, or the diarrhoea is still there after a week, that is your cue to have your child looked at, even if everything else seems fine.

The warning signs that mean see a doctor

Most children ride this out at home. But some need to be seen. Take your child to a doctor, or to the nearest emergency department if it is out of hours, if any of these appear:

• They cannot keep any fluid down. Every sip of water or rehydration solution comes straight back up.

• Signs of dehydration: fewer wet nappies or not passing urine for many hours, a dry mouth and tongue, no tears when crying, sunken eyes, or a sunken soft spot on a baby's head.

• Unusual drowsiness, floppiness, or being hard to wake. A child who is difficult to rouse is a same-day concern, always.

• Green (bile-stained) vomit, or vomit with blood in it.

• Blood in the diarrhoea.

• Diarrhoea lasting more than seven days, or vomiting lasting more than two to three days.

• A baby under six months with a lot of vomiting or diarrhoea. Small babies dehydrate quickly, so the threshold to be seen is lower.

• Severe, constant tummy pain, rather than the usual cramp-then-relief of a tummy bug.

A quick word on that last handful. Green vomit and blood are on this list because they can point to something other than a simple tummy bug, and they are worth a doctor's eyes the same day. This is the same principle I wrote about with fever in children and with dengue: it is not about panicking at every symptom, it is about knowing the few that change the plan.

Not sure if your child is dehydrated?

That judgement is hard to make at home, especially with a baby. If you are watching the nappies and still not sure, that uncertainty is itself a good reason to check. You can book an e-consult for guidance, or make an appointment to have your child seen.

What to do at home

The aim is not to stop the diarrhoea. The aim is to keep your child hydrated while their body clears the bug.

• Give fluids little and often. Small, frequent sips beat a big drink that comes straight back up. A spoon or a syringe every few minutes works better than a full cup once an hour.

• Use oral rehydration salts (ORS). These are the sachets you dissolve in water, sold at any pharmacy here. They replace water and salts in the right balance, which plain water alone does not. Offer more after every watery stool or vomit.

• Keep feeding. Keep breastfeeding right through the illness, more often if anything. If your child is on formula or solids, go back to their normal feeds once the worst of the vomiting has passed. Starving a child through a tummy bug does not help and slows recovery.

• Ask about a short course of zinc. The World Health Organization recommends zinc for young children with diarrhoea, because it shortens the illness and lowers the chance of it coming back over the next few months. The usual course is 10 to 14 days: 20 mg a day for children aged 6 months and older, and 10 mg a day for babies under 6 months. Zinc is sold at pharmacies here, so ask your pharmacist for the right one for your child.

• For fever or discomfort, paracetamol can help. Dose it by your child's weight, not their age, and check the label or ask your pharmacist. My fever guide walks through this.

Many parents here were raised on air garam gula, homemade sugar-and-salt water. The instinct is exactly right, that is what ORS is. The reason I still point parents to the pharmacy sachets is that the concentration matters, and it is very easy to get the homemade mix too salty or too sweet, which can make a dehydrated child worse. The sachets are pre-measured, so you take the guesswork out.

What not to do

• Do not give fizzy drinks or fruit juice to rehydrate. Sweet drinks like fruit juice, cordial, or carbonated drinks can pull more water into the gut and worsen the diarrhoea. This includes isotonic sports drinks like 100 Plus, which are made for sweating adults, not for a dehydrated child. ORS is what you want.

• Do not reach for anti-diarrhoea or anti-vomiting medicines for a young child unless a doctor has told you to. In small children these can do more harm than good.

• Do not expect antibiotics to help. Gastroenteritis is almost always viral, and antibiotics do nothing to a virus. Your doctor will decide in the uncommon cases where they are actually needed.

When your child should be in hospital

Some children need more than home care. A child should be assessed, and often admitted, if they show signs of significant dehydration or shock: very sleepy or hard to wake, sunken eyes, cold hands and feet, pale or mottled skin, breathing fast, or a racing heart. Children under one, and especially under six months, are watched more closely because they tip into dehydration faster.

If your child cannot keep the rehydration solution down at all, they may need fluids given another way, either through a tube or a drip, until they can drink again. That is a normal, routine step, not a sign that something has gone terribly wrong.

Can you prevent it?

You cannot childproof against every tummy bug, but you can cut the odds:

• Handwashing, properly and often, especially after nappy changes and before meals. This is the single most effective thing.

• Clean water and well-cooked food, and care with reheated food in the heat.

• The rotavirus vaccine. Rotavirus is one of the most common causes of severe diarrhoea in young children. The vaccine is given by mouth in the first months of life and is very effective at preventing the severe, dehydrating cases that land babies in hospital. In Malaysia it is not part of the free government schedule, but it is available at private clinics, and it is worth asking me or your own paediatrician about. More on this on my vaccinations page.

The bottom line

A tummy bug is miserable, and cleaning up at 3am is nobody's idea of fun. But for most children it is a passing illness that their body handles well. Your job is to keep the fluids going in small sips, watch the nappies, and know the short list of signs that mean it is time to be seen. Get those right and you have done the important part.

And if you are unsure, you do not have to decide alone.

Frequently asked questions

How long does diarrhoea and vomiting last in children?

Vomiting usually settles within one to two days and almost always within three. Diarrhoea usually lasts five to seven days and clears within two weeks. If vomiting lasts more than two to three days, or diarrhoea more than seven, have your child seen, even if they otherwise seem well.

How do I know if my child is dehydrated?

Watch the nappies first. Fewer wet nappies, or none for many hours, is the earliest practical sign. Others are a dry mouth, no tears when crying, sunken eyes, unusual sleepiness, and in a baby a sunken soft spot on the head. Any of these means your child should be seen the same day.

What can I give my child to stop the diarrhoea and vomiting?

The goal is not to stop it but to replace the fluid being lost. Give oral rehydration salts (ORS) from the pharmacy, in small frequent sips, and offer more after each watery stool or vomit. The World Health Organization also recommends a short course of zinc for young children, which shortens the illness, so ask your pharmacist. Avoid anti-diarrhoea and anti-vomiting medicines in young children unless your doctor advises them.

Should I stop milk or breastfeeding when my child has diarrhoea?

No. Keep breastfeeding right through the illness, more often if you can. For formula or solids, return to normal feeds once the worst of the vomiting has passed. Stopping milk does not help and can slow recovery.

Can I give my child 100 Plus, fruit juice or flat soft drink?

Better not. Sugary and fizzy drinks, including isotonic sports drinks, can pull water into the gut and make diarrhoea worse. Oral rehydration salts are designed for exactly this and are the safer choice.

Do antibiotics help with a stomach bug?

Usually not. Gastroenteritis in children is almost always caused by a virus, and antibiotics do nothing against viruses. They are only needed in the uncommon cases a doctor identifies, so they are not something to start at home.

Can the rotavirus vaccine prevent this?

It prevents the most severe cases. Rotavirus is a leading cause of severe, dehydrating diarrhoea in young children, and the oral vaccine given in early infancy is very effective against it. In Malaysia it is available privately rather than through the free government schedule. Ask your paediatrician.

When should I take my child to hospital?

Go straight away if your child cannot keep any fluid down, has green or blood-stained vomit, blood in the stool, is unusually drowsy or floppy, or shows signs of dehydration such as no urine for many hours and no tears. Babies under six months should be seen sooner rather than later.

Dr Nisa Khalil is a consultant paediatrician with a special interest in child development, with 18 years in paediatrics. She sees babies and children at ParkCity Medical Centre, Kuala Lumpur.

This article is general health information and does not replace an individual assessment by your own doctor. If you are worried about your child, seek medical care.