My Child Has Never Been the Same After a Stomach Bug

What parents need to understand when the infection is gone but the gut has not caught up.

Written and clinically reviewed by Bahee Van de Bor, RD, BCAPSc PGDipDiet, Specialist Paediatric Dietitian, former specialist dietitian at Great Ormond Street Hospital, with over 20 years of clinical experience in paediatric digestive health.

It started like any other school bug.

Vomiting, diarrhoea, a couple of days off, and then the fever passed.

The GP said it was viral, nothing to worry about, and sent you home.

That was two months ago.

Your child is still running to the toilet after meals.

Still getting tummy pain that arrives from nowhere.

Still having stools that look nothing like they did before.

And the tests, if you managed to get any done, came back completely normal.

You are not imagining it.

And your child is not doing it for attention.

This is one of the most common ways I see ongoing gut symptoms begin.

Most parents get told the same thing at this point.

Wait and see.

Give it time.

These things settle.

Often that is true.

Most children do recover fully.

But when weeks turn into months, wait and see stops being a plan.

And what nobody tends to explain is why.

Here is the question I would rather you asked.

Not when will this go away, but what is my child’s gut actually doing, and what does it need?

That question has answers.

This post is for parents who do not need the science right now.

If you want the mechanisms and the research, I have written that separately: Can a Stomach Bug Trigger IBS in Children?

This one is for when you just need someone to look at what you are describing and say: yes, I recognise this.

The infection may be gone. But the gut has not fully moved on yet.

The first place almost every family goes is: the infection must still be there.

The stools are still loose.

The pain is still there.

So something must still be causing it.

In most children the bug itself has long gone.

What you are seeing is the gut reacting to its own changed state, not to an active infection.

So what has actually changed?

The Rome V criteria, the framework used internationally to diagnose gut disorders in children, describe five mechanisms that can drive these conditions.

They are worth knowing by name, because between them they explain most of what follows.

• Abnormal gut motility. How quickly, or how slowly, things move through.
• Visceral hypersensitivity. The gut’s pain signalling turned up louder, so gas, food moving through and the ordinary stretch of a full stomach can hurt in a way they never used to. This heightened sensitivity is real, even though nothing shows up on a standard test.
• Impaired intestinal barrier function. The gut lining becomes more permeable than usual, and can stay mildly inflamed.
• Changes in the intestinal microbiota. The community of bacteria shifts, in variety and in balance. More on that in a moment.
• Abnormal brain-gut interaction. A change in how the brain reads the signals coming up from the gut.

Gastroenteritis is one recognised trigger for this kind of change.

Which of these it disturbs in your child, and how much, varies.

That is why these conditions sit in a group called disorders of gut-brain interaction, rather than being called a gut disease.

None of that is permanent damage.

It is several systems working differently at the same time.

It is confusing because it can look exactly like an ongoing infection.

And that difference changes everything about what helps.

Repeating the same stool culture over and over, hunting for a bug that has already cleared, is rarely what moves things forward.

But testing itself is not the enemy, and I want to be clear about that.

Checking for coeliac disease where diarrhoea is the main symptom, using faecal calprotectin to screen for inflammation, and considering parasites depending on where you live are all standard, and all worth doing.

NICE also says stool investigation is worth considering if diarrhoea has not improved by day seven.

And occasionally an infection has not fully cleared, which is one of the things a proper assessment is there to pick up.

If your child has ongoing loose stools, those are questions worth answering properly.

Ongoing gut symptoms after a stomach bug: six patterns I see in clinic

Ongoing symptoms after a stomach bug do not look the same in every child.

These are the six patterns that come up most often in my clinic.

Your child may fit one of them, or parts of two.

Loose stools or urgency that will not settle

The diarrhoea should have stopped by now.

It has not, or not completely.

Stools are looser than they used to be, more frequent, or harder to hold on to.

Some children start having accidents they are mortified by.

None of this is within your child’s control.

Urgency is frightening, and an accident at school is humiliating.

Plenty of children start quietly planning their day around where the nearest toilet is, long before they mention it to anyone.

Several things can cause this, which is exactly why guessing does not work.

The common ones are changes in gut movement or in the microbiota after the infection, temporary lactose malabsorption, a stool backlog leaking around itself, a diet that quietly narrowed during the illness, or occasionally an infection that has not fully cleared.

Which one it is matters, because the fix for each is different.

What changes in the gut microbiota

When researchers have looked at the gut bacteria of children with ongoing symptoms, they tend to find a change in the microbiota profile.

For example, fewer different species than in children without those symptoms, and a different overall mix among the ones that remain.

That is why, in my clinic, the aim is not to remove more foods at random.

It is to restore the gut, and to rebuild both the variety and the numbers of what lives in it.

So that your child stops feeling miserable about their tummy.

So that they can poo comfortably, without urgency and without pain.

And so that they can get back to doing normal kid things with their friends.

When foods that were fine stop being fine

Some children do find that foods they managed perfectly well before the bug now cause trouble.

That is real.

It is not fussiness, and you are not imagining the pattern.

For some children, easing back on certain foods for a while does help.

But which foods, how much, and for how long is not something to work out by trial and error at the kitchen table, and it is not the first thing to try.

Keep reading.

There is more on this further down, in the sections on tummy pain and on what actually helps.

More on this: Why Your Child’s Loose Stools Keep Coming Back

New constipation, or constipation with soiling

Some children go the other way entirely.

This surprises almost every parent, because a stomach bug means diarrhoea, surely.

Not always.

In that same prospective study, constipation was the most commonly diagnosed gut problem in the months after an infection, ahead of both tummy pain and IBS.

Worth knowing that the disorders which stood out most clearly against the children who had not been infected were the pain-related ones, so this is about what turns up often, not about what the infection is proven to cause.

Here is how it happens.

The bug left your child eating and drinking less.

The first poo afterwards may have been hard or painful.

And something filed that away as: avoid the toilet.

So they hold on.

A backlog builds.

Then the backlog starts leaking liquid stool around itself, which looks for all the world like diarrhoea or accidents.

If your child’s tummy is bloated or uncomfortable alongside what looks like loose stools, ask your GP whether overflow could be the cause.

It is easily missed, and the management is very different from ordinary diarrhoea.

More on this: Why Is My Child Still Constipated After a Stomach Bug?

Tummy pain and bloating that keeps coming back

The illness is over, but pain is a regular feature now.

Around meals.

After certain foods.

Sometimes with no trigger you can spot at all.

After a gut infection, the gut’s pain signalling can turn up louder.

The clinical name is visceral hypersensitivity, and it means the gut is working normally but its alarm system fires too easily.

Think of it as the volume dial being stuck up.

Same amount of gas, same food moving through, much louder signal.

Your child is not making it up.

You have probably also noticed that certain foods seem to set it off.

That is not your imagination either.

What about FODMAPs?

According to the Rome V criteria, more than nine in ten children with IBS can name at least one food that makes their symptoms worse.

Often the thread running through those foods is a group of carbohydrates called FODMAPs.

The name stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols.

In plainer terms, a group of carbohydrates that the small intestine absorbs poorly.

They draw water into the gut and then ferment, and the result can be tummy pain, bloating and a change in stool pattern.

You will find them in everyday foods.

Apples, onions, wheat, milk, and some sweeteners.

So can FODMAPs be a genuine trigger for your child?

In some children, yes, they can.

In my clinic, the children who respond best to adjusting FODMAPs tend to be those whose main problem is loose stools and chronic tummy pain.

But that is a pattern I notice, not a rule you can apply to your own child.

Every child needs assessing individually.

The difficulty is knowing where to start.

Before the pattern has been properly assessed, it is too early to assume FODMAPs are the problem.

Broadly removing them is more likely to narrow your child’s diet than to settle their gut.

There is also a point where the diagnostic picture changes, and it is worth being precise about what changes and what does not.

To be clear, you can see your GP at any point you are worried.

Nothing here asks you to wait.

But if your child is six or over, and still has tummy pain alongside a change in their usual stool pattern, and that has been going on for at least eight weeks, this is the earliest point at which a doctor can meaningfully consider IBS.

That is what the Rome V criteria ask for.

Pain on average at least four days a month, linked to going to the toilet or to a change in how often or how formed the stools are, present for at least two months.

Rome V sets six as the minimum age for the diagnosis, because no studies have described IBS in children younger than that.

That is about the label, not about your child.

A younger child with the same symptoms still needs assessing, and can still be helped.

Now, a diagnosis is one thing.

What to do about food is another, and the two do not run to the same timetable.

Whether adjusting FODMAPs is worth considering depends on your child’s symptoms, how severe they are, their growth and what they are already eating.

Not on a date in the calendar.

In some children, carefully targeted changes to particular FODMAPs help.

In others, something else matters more.

And whatever the diet, any restriction in a child should run under the supervision of a registered paediatric dietitian trained in working with children with suspected IBS, never attempted alone.

Dairy suddenly seeming to cause problems

Milk, yoghurt and cheese were fine before the bug.

Now they seem to bring on bloating, cramping or loose stools.

This is real, and it is well described.

During and after a bout of gastroenteritis, children can temporarily stop producing enough lactase, the enzyme that digests the sugar in milk.

The infection damages the gut lining, and lactase is made right at the tip of that lining, so it is the first thing to go.

The lactose then sits undigested and ferments, which is what causes the bloating and the loose stools.

What does the research tell us?

A Cochrane review pools every trial that has asked the same question, rather than resting on any one of them.

The one covering this pulled together 33 trials and 2,973 children.

It found that removing lactose shortened diarrhoea by around 18 hours on average, and roughly halved the chance of treatment failing.

That evidence is about the acute illness and the days just after it, not about symptoms still going weeks later.

The good news is that lactase production usually recovers as the gut lining heals.

Here is the part worth holding on to.

Where tummy pain has become the main problem rather than the diarrhoea, lactose is usually not the culprit.

When researchers have tested this properly, giving children lactose or a placebo without them knowing which, most trials found no difference.

Not all of them, so it is not a closed question.

But in children who do have lactose intolerance, dealing with the lactose does help.

Giving the lactase enzyme reduced bloating, diarrhoea, pain and wind.

So the question is not whether to fear dairy.

It is whether lactose is actually your child’s problem, and that is worth knowing before you take a whole food group away.

More on this: Is My Child Suddenly Reacting to Dairy After a Stomach Bug?

Eating less, or getting anxious around food

Your child is eating less than they were.

Refusing things they used to like.

Nervous before meals in a way that was not there before.

For a lot of children this is learned.

They worked out that eating leads to pain, so they eat less to stay comfortable.

And often, by this point, you have been removing foods too, hoping to find the culprit.

Dairy goes first.

Then gluten.

Then certain fruits.

The reactions keep happening.

Here is what is often driving that.

Not a new intolerance to one specific food, but a gut that has become more reactive to eating itself.

The signal between gut and brain is amplified, so a normal meal can trigger a stronger response than it used to.

Often, it is not the food that changed.

It is the gut’s reaction to the act of eating.

That is not the whole story for every child.

Temporary lactose malabsorption, or particular FODMAPs, do contribute in some, which is exactly why it is worth looking rather than guessing.

Which is why I do not recommend removing foods at random at this stage.

The diet narrows, fibre and nutrient intake can fall, and mealtimes get frightening for everybody.

By the time I see these children, some are eating fewer than ten foods.

And this is where it stops being only about symptoms.

The Rome V criteria are explicit about it: because of the risk of disordered eating and avoidant restrictive food intake disorder, a dietitian should be involved in any restriction diet in a child, and the restriction should be loosened again as soon as it can be.

Not eventually.

From the start.

The intervention is not always the problem.

The sequence is.

Normal test results, with symptoms that carry on

Bloods have been taken.

Everything came back normal.

And you are sitting with a child who is still not right, wondering how someone who looks fine on paper can feel this unwell.

Tests are chosen to look for particular causes.

Inflammation, coeliac disease, infection, another medical condition.

Normal results are real reassurance about the things those particular tests were designed to find.

What they cannot do is measure every aspect of how the gut is working.

So normal results do not mean nothing is going on.

Here is the part that rarely gets explained.

There is no single blood test, biomarker or scan that confirms IBS.

Conditions like IBS are diagnosed from the pattern of symptoms, which is exactly how the Rome V criteria are written.

So if IBS turns out to be the explanation, routine tests were never going to confirm it.

That does not always mean the wrong tests were done.

It means the tests that were done cannot answer this particular question.

The investigation needs to shift from structure to function.

And a normal result does not, on its own, confirm a gut-brain disorder like IBS either.

That is a positive diagnosis, made from the whole picture: your child’s history, the pattern of their symptoms, and proper clinical assessment.

Why some children take longer to recover

You have seen the GP.

Most children come through this needing nothing more than time and a normal diet.

Some do not.

In my clinic, some of the children whose symptoms persist were already prone to gut symptoms before the bug.

Separately, the Rome V criteria cite a systematic review linking continuing tummy pain in children with a number of factors, gastroenteritis among them, alongside lifetime stress, poor sleep and having a parent with IBS.

If you want the mechanisms and the research behind post-infectious IBS in full, I cover all of it here: Can a Stomach Bug Trigger IBS in Children?

What actually helps a child’s gut recover after a stomach bug

The most common dead end I see is a family still searching for an infection, long after it has cleared.

Most children do recover.

Some need support to get there, and that support has to come in the right order.

So the first job is working out which pattern your child actually has.

A child with post-infectious constipation needs a different approach from a child with ongoing loose stools, and different again from a child whose main problem is pain and a shrinking diet.

Treat one as though it were another and progress stalls.

This is why I do not start with food exclusions or a list of supplements.

I start with assessment.

• What is the gut doing?
• What changed, and when?
• What have you already tried, and what happened when you did?

Once that picture is clear, the plan follows from it.

And then we build back.

Slowly, deliberately, rebuilding the variety the gut needs.

For some children this moves quickly.

For others, especially those who have been on restricted diets a long time, it takes a while.

But the direction of travel is towards more food, not less.

That is not just my preference.

For children who follow a reduced FODMAP trial, Rome V sets out three phases.

1. Restriction, for no more than four to six weeks.
2. Reintroduction.
3. Personalisation.

Restriction is a phase.

It was never the destination.

When to see your GP

Many children whose symptoms carry on turn out to have what doctors call a functional cause.

That means the gut is working differently, not that the infection has damaged it.

But do not assume that until a doctor has properly assessed your child.

Some features need your GP to look at first.

The Rome V criteria list these important symptoms for children with ongoing diarrhoea.

Symptoms you might notice at home:

• Unexpected weight loss
• Poor nutrition, delayed puberty, or growth slowing down
• Loss of appetite
• Signs of dehydration
• Diarrhoea at night, or very large volumes
• Vomiting that keeps returning, or happens at night
• Blood in the stool
• Blood in the urine
• Tummy pain alongside the diarrhoea
• Swelling, a distended tummy, or tenderness when you press
• Fever
• A skin rash, or joints that are sore or swollen
• A visible parasite passed in the stool
• A family history of inflammatory bowel disease, coeliac disease or bowel cancer
• Stools that are pale, greasy or unusually foul-smelling

One exception, and it matters. Green or yellow-green vomit is not a wait-for-the-GP symptom. NHS advice is to call 999 or go to A&E.

Your GP may also check for anaemia, a low platelet count, a raised white cell count, or raised calprotectin, CRP or ESR.

Those are all on the same Rome V list, and they are the reason a blood or stool test is sometimes worth repeating even when an earlier one was clear.

Now, on timing.

For children under five, NICE guidance says diarrhoea usually lasts five to seven days and has stopped within two weeks in most children.

Vomiting usually lasts one to two days and stops within three in most.

So if a young child’s diarrhoea is still going beyond two weeks, speak to your GP rather than waiting it out.

Beyond that, please do not wait for a milestone before asking for help.

If you are worried, see your GP.

That holds at two weeks just as much as at two months.

Daily tummy pain, missed school, growing fear of food, or a whole family reorganising itself around one child’s gut are all reason enough on their own.

So is having already tried removing foods, without any lasting improvement.

The eight-week mark mentioned earlier is a different thing entirely.

It is not the point at which you are allowed to be concerned.

It is the point at which a doctor can meaningfully consider IBS, because the Rome V criteria ask for tummy pain alongside a change in stool pattern, present for at least two months.

That applies to children aged six and over.

Rome V sets six as the minimum age, because no studies have described IBS in younger children. That is a limit on the label, not on getting your child seen.

Frequently Asked Questions

References

1. Pensabene L, Talarico V, Concolino D, et al. Postinfectious functional gastrointestinal disorders in children: a multicenter prospective study. The Journal of Pediatrics, 2015;166(4):903-907.E1.
2. Di Lorenzo C, Saps M, Chumpitazi BP, et al. Lower and Biliary Disorders of Gut-Brain Interaction: Child and Adolescent. Gastroenterology, 2026;170(6):1367-1387.
3. Saps M, Pensabene L, Di Martino L, et al. Post-infectious functional gastrointestinal disorders in children. The Journal of Pediatrics, 2008;152(6):812-816.E1.
4. MacGillivray S, Fahey T, McGuire W. Lactose avoidance for young children with acute diarrhoea. Cochrane Database of Systematic Reviews, 2013, Issue 10, Art. No. CD005433.
5. Nurko S, Benninga MA, Solari T, Chumpitazi BP. Pediatric aspects of nutrition interventions for disorders of gut-brain interaction. The American Journal of Gastroenterology, 2022;117(6):995-1009.
6. Lebenthal E, Rossi TM, Nord KS, Branski D. Recurrent abdominal pain and lactose absorption in children. Pediatrics, 1981;67(6):828-832.
7. Dearlove J, Dearlove B, Pearl K, Primavesi R. Dietary lactose and the child with abdominal pain. British Medical Journal (Clinical Research Edition), 1983;286:1936.
8. Gremse DA, Nguyenduc GH, Sacks AI, DiPalma JA. Irritable bowel syndrome and lactose maldigestion in recurrent abdominal pain in childhood. Southern Medical Journal, 1999;92(8):778-781.
9. Medow MS, Thek KD, Newman LJ, Berezin S, Glassman MS, Schwarz SM. Beta-galactosidase tablets in the treatment of lactose intolerance in pediatrics. American Journal of Diseases of Children, 1990;144(11):1261-1264.
10. National Institute for Health and Care Excellence. Diarrhoea and vomiting caused by gastroenteritis in under 5s: diagnosis and management (CG84). NICE clinical guideline CG84, published 22 April 2009, last reviewed 31 October 2018.