stomach flu in kids

Handling the Stomach Flu in Kids – Everything Parents Need to Know

When to call the doctor, what to expect, and how to help your little one feel better!

by Steve Silvestro, MD  @zendocsteve

You can also listen to this article as a podcast on your favorite podcast app or click on the player below:


Ah, vomiting and diarrhea! It’s a topic that no one really loves, but every single  parent will have to deal with—and probably more often than you’d like.

So, chances are that you’re reading this right now because either 1). you are a studious parent and want to make sure you’re prepared for all the potential challenges that you’ll face in the world of parenting (hats off to you!)—or 2). your child currently has a stomach flu, you’re in between changing sheets for the third time, and you’d like to figure out how not to make it a fourth time!

Either way, just about everything you need to know about handling vomiting and diarrhea in your child is covered right here.

And while this is the exact information I would give to my own patients, please remember that I unfortunately can’t treat your child via an article, so call your pediatrician should you have any concerns about your child.

We’ll start with some basics on when to call, then dive into exactly what you can do to help your child & what to expect.

*Note: While commonly called a “stomach flu” or “stomach bug,” these illnesses are almost always caused by viruses—and not necessarily the flu virus. I’ll use “stomach flu” and “stomach virus” interchangeably throughout this article.


I often get calls from parents who’ve panicked after their child has thrown up a few times and they’re unsure what to do.

The truth is that even though they can be unsettling to witness, most episodes of vomiting or diarrhea are not emergencies and can be easily managed at home (more on that later). However, there are certain situations that demand a call to your doctor, sometimes urgently. So I’ve broken these down into “call now” and “call during business hours” categories:


Call Your Doctor Now (Day or Night)

The following situations are urgent enough that you should call your doctor no matter what time of day it is, as some of these may require a visit to the ER.

  1. Your baby is less than 3 months old, has a distended belly, and is vomiting.

This could be something called “malrotation,” whereby the intestines are turned the wrong way and can kink. It’s quite rare and can technically happen at any age, but 50% of the time it occurs in the first month.

  1. Your child is showing signs of dehydration—explained in detail below.
  1. There is a significant amount of blood in diarrhea or vomit. If you can fill a shot glass with blood, I want to hear about it right away.
  1. If your child simply can’t keep any amount of fluid down over the course of a few hours—even if you only offer a teaspoon at a time.
  1. If your child has vomiting alone (meaning no diarrhea) and ANY of these:
    • Stiff neck
    • The light hurts your child’s eyes
    • Fever that won’t come down at all within 1-2 hours of giving the right dose of Tylenol or ibuprofen (download my free dosing guide at the blue bar on this page to make sure you’re giving the most accurate dose).
    • If your child has vomited 2 or more times after hitting her head


Call Your Doctor During Business Hours

The following are issues that your doctor should be told about, but that can usually wait until normal business hours. They may need treatment, but aren’t typically urgent emergencies.

  1. If there is a very small amount of blood in multiple bowel movements or vomits.

When a very small amount of blood is present in one hard poop, it’s usually due to a small tear in the anus caused by constipation. Likewise, when a very small amount is present with one episode of diarrhea or vomiting, it’s usually from minor irritation. But if there is blood—even a small amount—present in multiple bowel movements or episodes of vomiting, then it may be due to other issues that your doctor will need to evaluate.

  1. If diarrhea has lasted longer than 2 weeks.

It sounds crazy, but “normal” diarrhea from a stomach flu can last for several days, especially in kids. But if it’s gone on longer than two weeks, then your doctor should check for less common infections or other problems that might need treatment.

  1. If your child can keep most things down, but is throwing up a couple times a day for more than 3-4 days in a row.

Also, talk to your doctor if your child doesn’t throw up every day, but seems to throw up a few days a week for several weeks.


In case you haven’t noticed, babies make life a bit more complicated. The same is true when trying to tell whether your baby threw up or just spat up, or whether that blowout diaper should qualify as diarrhea.

Most babies spit up at some point, and some babies spit up all day long. And for others (like my first…), it can occasionally seem like they’re bringing up everything they just ate. The result is that it can sometimes be hard to tell whether your baby is just spitting up or vomiting.

The best way to determine what’s what is to get a sense of how what you’re seeing compares to what you usually see. Is it a whole lot more—as in, usually a burp cloth will do, but suddenly today you both need three extra showers?

Another way to tell is to look at how often it’s coming up. When a baby vomits because he’s sick, the gut usually spasms—meaning that you’re likely to see more episodes over the next few hours. So multiple large episodes over a couple of hours means you’re more likely dealing with real vomiting rather than spit-up.

A similar approach can help you tell whether your baby has diarrhea. It’s not uncommon for babies to have blowouts here and there. But if every diaper is suddenly leaking out the bottom and up the back—especially if the poop seems more watery than slimy—then your baby probably has diarrhea.

Call your doctor if your baby is less than 3 months old and seems to have projectile vomiting (as in, “here to the wall”) after every feeding. This may be a condition called “pyloric stenosis” whereby the muscle between the stomach and small intestine is too large. It’s somewhat rare and stereotypically occurs more often in first-born boys around a month of age—but it can develop in any baby in the first few months of life and requires surgery to fix, so call your doctor if this seems to be happening in your baby.



Okay, before we dive into the nuts & bolts of stomach viruses and how to treat them, let’s wrap up this “what to watch for” section by talking about dehydration.

Dehydration is the big baddie when it comes to stomach viruses—it’s the complication that can not only make kids feel worse, but also potentially land them in the hospital. So this is the thing you really need to know how to assess.

Some of the more common signs you’ll read about have to do with your child simply looking “dry.” She might not make any tears when she cries, or his mouth will be very dry or sticky. In a baby, you might notice that the soft spot on the top of the head is very sunken (keep in mind that the soft spot can change, sinking a little sometimes or raising slightly at others—but a big change may be worrisome).

But the most useful way to monitor dehydration is to look at how much your child is peeing. This is usually the first sign of dehydration and the best one for you to use to judge at home. My general breakdown is that a child under 12 months of age needs to give you about 4-5 good wet diapers over 24 hours. Or it could be the equivalent—if you’re getting maybe 8 or 9 half-diapers, that counts, too. For a child who’s 12-18 months old, we want to see about 3-4 wet diapers in a day; an older child needs at least 2 or 3 really good diapers or pees over 24 hours. Some people will even break it down to say that you want at least one every 8 hours.

If you’re not hitting these numbers, then that’s your first sign that your child is dehydrated. If that’s the case, you can try the hydration techniques we’ll discuss below—and if that still doesn’t work, then you need to call your doctor (remember, of course, that you can always call your doctor any time you are concerned!).


What follows are a few sentences of the science of what’s going on when your child has a stomach flu—but don’t skip it! Understanding this goes a long way in understanding how to properly feed/rehydrate your child and why some complications come up later.

When you eat food, it goes down your esophagus, to your stomach, then small intestine, then large intestine, then out. Your small intestine is lined by finger-like projections called “villi.” Imagine going through a tunnel and instead of it being smooth, the walls, ceiling, and floor are lined by those brushes in a drive-through carwash. That’s the inside of your intestine. The space all along these finger-like projections is where nutrients from food get absorbed.

With a stomach flu, those finger-like villi get flattened out. That means that you can’t absorb things as well as you usually should. The result is that the inside of the intestine is more concentrated than usual, which causes more water to spill in by osmosis—ultimately resulting in watery diarrhea. Vomiting can be caused by this inflammation, as well as inflammation in the stomach itself or a host of other issues.

One of the biggest things in kids’ diets that gets absorbed along the intestinal villi is lactose from dairy—which is why when your child has a stomach flu and those villi are flattened out, giving regular milk can sometimes either make the diarrhea worse or make it stick around a lot longer.

It takes several days for those intestinal villi to heal and function properly. In the meantime, you might see that your child’s appetite isn’t quite normal, and he might complain that his tummy hurts.

All of this combines to leave your child feeling miserable and you feeling miserable for your child!

So enough of that—let’s talk about what you can do to help.



Helping your child through vomiting can feel like a slog, but it’s really very simple when you break it down: “Go slowly and focus on hydration.”

Follow these steps to help with vomiting:

  1. Hold off on food.

We parents have a hard time seeing our kids not eating. But here’s the thing—if you had an upset stomach, you probably wouldn’t eat for a day or two. Food is great and all, but remember that the most important thing is to keep your child hydrated. Focus on hydration first—it’s okay if your child doesn’t eat for a few days as long as she stays hydrated.

  1. Know what drinks you should give.

If your child can’t keep any food down, then don’t try to keep her hydrated with water. Giving water alone will dilute out the electrolytes in your child’s bloodstream. This is bad. Instead, you need to give something that has a small amount of sugar, plus sodium and potassium. Oral rehydration fluids like Pedialyte (found at most pharmacies and grocery stores) are designed to perfectly match what the body needs to stay hydrated. Sports drinks like Gatorade are a somewhat acceptable second choice if you can’t find Pedialyte or need something in a pinch.

For babies, breastmilk or formula are fine, as long as your baby can keep it down. The best approach is to start with small volumes of milk, which brings us to #3.

  1. Start with frequent, small amounts of fluids.

*This is the most important step—and skipping it is the most common reason parents have a hard time with vomiting. If you give your child a full bottle or glass of something to drink, you’re basically asking them to throw it back up at you.

For an infant, offer only 1-2 teaspoons (5-10mL) of fluids every 10-15 minutes. If your child can keep that down for about 2-3 hours, you can try twice as much for a while. Once 6-8 hours have passed since the last time your child vomited, you can return to normal volumes of feeds.

For kids over a year old, you can start with a tablespoon (15mL) every 5-10 minutes for the first 1-2 hours. If they can keep that down, then you can try to slowly advance to bigger volumes.

  1. Know when to bring food back.

If your child hasn’t thrown up for at least 8 hours, you can bring food back on board. When parents call me in the late afternoon to report that their child has started vomiting, I tell them not to even bother trying dinner. When you bring foods back on, start with bland foods first—think crackers, apple sauce, toast. However, be sure to get back to regular food within about 24 hours so that you can provide adequate nutrition and help your child recover faster.

  1. Monitor closely for dehydration using the guidelines above.


Remember how I said you should call your doctor if your child’s diarrhea lasts for more than two weeks? Diarrhea can stick around for a while and still be considered a “normal” stomach virus. Luckily, the worst period with the most frequent episodes of diarrhea will usually only be the first few days, with the number of episodes ideally slowing down as the illness moves on.

Like with vomiting, the key things to remember are to focus on hydration and know when you start feeding your child again.

Follow these steps to help with diarrhea:

  1. Replace each episode of diarrhea with about an 1-2 ounces of fluid (30-60 mL) if your child is able to keep it down.

Of course, if your child is also vomiting, then you’ll have to do the frequent-small-amount approach we just talked about until she can keep bigger volumes down.

  1. Know what fluids to give—and avoid.

Again, if there is a lot of diarrhea, you’ll want to give fluids that have a small amount of sugar, plus some sodium and potassium—something like Pedialyte. If your child has only a small amount of diarrhea—say, once or twice a day—isn’t vomiting and is over 6 months old, then water should likely be fine.

A breastfed baby can keep drinking breastmilk. If you give formula, however, you may want to consider a lactose-free or soy formula for a few days. (Remember: lactose is absorbed along those intestinal villi—and those villi aren’t working so well right now.)

Avoid milk and high-sugar sports drinks. Remember: lactose and other sugars are absorbed along the intestinal villi—and those villi aren’t looking so hot right now. As a result, that sugar hangs out inside the small intestine & pulls more moisture in by osmosis—essentially worsening or prolonging diarrhea. We want the opposite to happen, so avoid these drinks if you can!

  1. If your child only has diarrhea and isn’t vomiting, then you can keep with a regular diet.

We used to talk about giving a BRAT diet—bananas, rice, apple sauce, and toast—but now many pediatricians will say that if your child can keep food down without vomiting, then you should give real food. The idea here is that you’re going to add more bulk to your child’s bowel movements, plus you’re going to give better nutrition than you would with a BRAT diet.

Now, if there is very frequent diarrhea, then you may want to give the BRAT diet for part of a day or even a full day just to help slow things down—but don’t do it for more than a day.

  1. Monitor closely for dehydration using the guidelines above.



When it comes to vomiting and diarrhea, it’s not always over when you think it is…

Delayed Return to Normal Appetite

Almost every parent I know stresses out when their child isn’t eating. It doesn’t help that grandma is always telling you your kid looks skinny—and after a stomach virus, he really might look a bit worse for the wear.

But it can take several days after your child has stopped with vomiting or diarrhea before her appetite can seem back to normal. Why so long? Remember those little intestinal villi? After the virus has cleared and the inflammation is gone, those little guys have to get back to normal size and function again. Not only that, all the normal, healthy bacteria that populate the gut and help keep us healthy have to get their act back together, too.

All of this can take a bit of time—it might be a full week after your child seems well before her belly feels comfortable enough to eat normally again.

Expect the Stinger of Vomiting!

Sometimes, however, a kid on the mend will eat before his gut is healthy enough to handle it. I can’t tell you how many times I get this phone call:

“My child vomited for a day or two and then seemed fine, but then threw up again two days later! The stomach bug isn’t getting better!”

This is so common, in fact, that I make a point to warn parents about it when I first diagnose their child with a stomach bug (partly to preventatively ease their worries and, yes, partly to save myself the phone call!).

What’s happening here is that the child’s gut has started to heal enough that his appetite is coming back—but not healed enough to handle the type or amount of food he just ate.

In this scenario, your child isn’t getting sick again; he’s on the mend, but needs to go a bit more slowly with the food for a few more days.

Expect Rebound Constipation After Diarrhea

Yup, out of the frying pan and into the fire.

We talked about how the intestinal villi in the small intestine help absorb nutrients from food. Well, we haven’t talked about the large intestine. This guy’s only job is to suck water out of poop so that you don’t have diarrhea all the time. That’s it.

With a stomach virus, the large intestine isn’t usually affected—at least, not as much as the stomach and small intestine usually are. And that’s helpful, because if the large intestine couldn’t do its job during a stomach virus infection, then diarrhea would be WAY worse.

When your child has diarrhea, the large intestine starts to work overtime, sucking as much water out of the poop as possible to try and minimize the diarrhea. But after the small intestine’s villi start to heal and the poop making it to the large intestine is getting less diarrhea-like, there can sometimes be a lag in how quickly the large intestine recognizes that. Add this to the fact that there hasn’t been much solid food in your child’s belly for a while and the result is that many kids with diarrhea will end up constipated for a few days after the diarrhea has gotten better.



Sure. Maybe. We don’t know.

See, the problem with talking about “probiotics” is that it’s a lot like talking about “antibiotics”—you really need to know which strain you’re talking about, what dose you’re giving, and what aim you’re targeting. The field of gut bacteria is rapidly developing and we’re learning more information (and asking more questions!) all the time.

The truth is that for an acute stomach virus lasting just a few days, a probiotic supplement may not work fast enough or strongly enough to make the symptoms end significantly faster.

A better approach is to fortify your child’s gut bacteria before she even gets sick. We know the food good gut bacteria eat is fiber from plants, and that the people with the most plants in their diets have the widest variety of gut bacteria. So keep working on getting those fruits and veggies into your kids!

For more on this topic, see my interview with gut health expert Dr. Will Bulsciewicz here.



It’s okay to admit that after a few days of cleaning up bodily fluids from every possible orifice, you’re probably feeling ready to get your kid out of your house as soon as possible.

But here’s the bad news first: For many common stomach viruses, your child can keep passing the virus in her poop for anywhere from a few days to a couple of weeks.

And here’s the good news: However, most of us pediatricians will say that your child can go back to school or daycare 24 hours after she’s stopped throwing up.

If diarrhea is the main issue, it’s really all about your child’s comfort level and hygiene. For older kids who are in school, it’s okay to send them if 1). They’re good about washing their hands after using the bathroom (otherwise they might spread the germs), and 2). They aren’t going so frequently that they’ll be uncomfortable in class all day.

As for children in daycare or preschool, ask about the daycare or preschool’s policy. Diarrhea from a common stomach flu can last as long as two weeks, so as long as everyone washes their hands well, diarrhea really shouldn’t be a factor that keeps a child home for more than a day or so. Vomiting is a much stronger reason to be kept home.



“Glove up before cleanup.”

Hey, I love my kids. I want to comfort them and help them when they’re sick.

But I also know that if I catch a stomach virus while I’m trying to care for them, we’re both screwed.

So as harsh as it might sound to some, when my kids were young and would throw up when sick, I wouldn’t rush to their side first. Instead, I’d take the extra minute to go find the box of nitrile gloves I keep at home and glove up before I’d go to help them clean up.

I suggest you do the same. Your child’s already sick and feeling crummy. An extra two minutes to make sure you don’t end up feeling the same is well worth it. It’s hard to nurse your kid back to health when you’re the patient, too!

Well, look at that—this turned out to be 9 pages about vomiting and diarrhea… But unlike other medical sites & resources that just give you a paragraph or two and some bullet points, it’s important to me that you understand the whole picture when it comes to your kids’ health—what’s going on, why it’s going on, what to do, what to watch for, and what to expect.

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Handling the Stomach Flu in Kids - Everything Parents Need to Know