Fever in Children: What to Do & When to Worry
This is EVERYTHING parents need to know about fevers!
by Steve Silvestro, MD @zendocsteve
This article can also be listened to as a podcast in your favorite podcast app or in the player below:
Disclaimer: Your child’s health is important—really important. The advice from a doctor in an article cannot match your own insight about your child and the advice of the doctor who knows your family best. If you ever have any concern about your child’s health, please call your pediatrician.
A few years ago, I received a voicemail that I’ll never forget.
The mom of an 18-month-old called because her daughter had a fever of 100.8. Now that’s not an unusual story to hear, lots of toddlers get little fevers. What stood out was that on the voicemail, the mom was crying. And when I called her back, she was still crying—because it was her daughter’s first fever, and she, the mom, was scared.
I talked with her, I listened as she spoke about how her daughter was feeling; we talked about how to help her feel better, and what she should look out for. Afterward, I went onto Facebook and I wrote a post with about 15 bullet points about fevers—why we get them, how to treat them, when you do and don’t have to worry, etc.—and I made the post public. Within days, it had dozens of comments and hundreds of likes. I was astounded by how well people responded to the information, and the experience gave birth to The Child Repair Guide Podcast, now an award-winning podcast that’s still growing.
Fever is universal, everyone gets fevers, most especially kids, and yet they can still inspire so much anxiety in us as parents. It’s gotten to be that a fever alone is something that is seen as scary.
But it doesn’t have to be this way.
My hope is that the information in this article is going to help your child having a fever become less of an intimidating experience because you’re going to know exactly what to do and when you do or don’t need to worry.
So in this article, we’ll cover:
- What a fever is & how to check for it
- What numbers matter and for whom
- We’re going to talk about how the exact number doesn’t actually matter for most people—and what does instead
- When a fever should warrant a phone call to your doctor, or even a trip to the Emergency Room
- How and when to best treat a fever (for more details, download my FREE Children’s Medication Dosing Guide via the blue bar at the bottom of this article)
- How to know when your child is better & not contagious
WHAT IS A FEVER?
More often than not, a fever is part of the body’s response to help fight off an infection.
Many of the viruses and bacteria that cause infections like to hang out at body temperature, but they don’t do so well when the temperature gets higher. So, the body releases natural chemicals to elevate your temperature in an effort to kill off as many of those germs as possible.
Kids are prone to getting fevers—and sometimes pretty high fevers, even with common colds—because their bodies are seeing these germs for the first time or the second time. As a result, they mount a strong response to try and fight those germs off.
We adults get sick less often because we’ve already built up immunity against many germs—our bodies don’t need to bring out the big guns to fight a cold, so we’re more likely to just get a runny nose or a cough without a fever.
But because the average child is expected to get sick between 8 and 12 times a year, you can expect that a fever will be a common occurrence in your household.
WHAT COUNTS AS A FEVER?
Now when we talk about fever, there is a very specific number that we doctors use as the cutoff to say that you officially have a fever: 100.4°F or 38°C.
Of course, there’s some variability depending on where you check. The National Institute of Health (NIH) says that a fever is when you have a:
- rectal temperature of: 100.4°F (38°C)
- 99.5°F (37.5°C) measured in the mouth (orally)
- 99-99.5°F (37.2°C) measured under the arm (axillary).
You’ll get some different thoughts from other sources about how much variation there is between rectal, oral, and armpit measurements, but this is a good rough idea.
However, many of us doctors will really hold firm to the idea that you don’t have a fever unless you get 100.4—no matter where you check—so it’s a little up in the air.
WHAT THERMOMETER SHOULD YOU GET?
When parents ask me which thermometer they should buy, I tell them to get an oral/axillary/rectal thermometer that costs less than $10.
It’s true—I’m a pediatrician, and the thermometers I use with my family are generic, cheap-o thermometers from CVS and Target.
Because the exact number doesn’t actually matter that much, unless 1). Your child is under 3 months old, or 2). Your child has a medical condition where having a fever is a big deal—and we’ll get to that shortly.
There are a few other things you should think about when buying a thermometer:
1). Rectal temperature is the gold standard—especially for infants.
As uncomfortable as it might be, it’s the most accurate way to measure the body’s core temperature. And for babies under 3 months, it’s the only way to get an accurate temperature. The issue with babies is that they have so much surface area for their size, that they lose heat everywhere—that’s why hats are important for newborns when the temperature drops—so the only way to accurately check in a baby is a rectal temperature.
2). Ear thermometers are easy, but not always accurate.
I’m not really fond of ear thermometers because there can be so much variability—coming in from the cold or wearing a hat can affect the temperature you get—but I know that they’re easy to use, especially on a feisty kid who doesn’t want to sit still. A fever in the ear is roughly close to either the oral or armpit measurements.
3). Affordable forehead thermometers aren’t always accurate, either.
With forehead thermometers (also called temporal thermometers), some researchers will say that they’re close to a rectal temp—so, close to the true body temperature—but there’s some variability there, too. You can go onto Amazon and buy a forehead thermometer for as little as $30 and as much as $300+—and there’s a mighty difference in the accuracy between the two. We use an expensive forehead thermometer in my office, but I wouldn’t recommend spending that much for home use.
4). Basic thermometer rule:
When choosing a thermometer, you want one that seems to give you reasonable numbers (so no one should be hitting 94s) and tends to be pretty consistent, meaning that you’re not getting 98.3°F in one moment, then 100.8°F five minutes later.
THE HEIGHT OF THE FEVER DOESN’T MATTER, UNLESS…
Okay, so I said a few moments ago that unless your child is under 3 months old or has certain medical conditions, then the exact temperature doesn’t really matter. Before we discuss why that’s true, let’s talk about these two categories of kids first.
For a baby less than 12 weeks old, a fever is a big deal.
The issue here isn’t that an infant’s immune system is weak—it’s actually pretty strong. No, the problem is that a baby’s nervous system is immature for the first few months.
That means that a baby who’s less than 12 weeks old and has a fever might look and act the same whether the fever is due to a cold or something much nastier, like meningitis. Plus, newborns are susceptible to bacteria from delivery—and can therefore get nasty infections like meningitis—through the first several weeks of life.
As a result, if a baby has a rectal fever of 100.4°F or higher, then you need to go to the ER. [Of course, you may call your pediatrician first, but she will likely send you to the ER]. Don’t give your baby acetaminophen (Tylenol) before you go, because the doctors need to see whether or not there really is a fever before they start testing to find out why.
A fever can be serious if your child has certain medical conditions.
If your child has certain medical conditions—cancer, HIV, sickle cell, and any one of a handful of other things (and if your child is in this category, then you probably already know this), or is on immunosuppressive medications—then your child is at risk for either more serious infections or for worse outcomes with even just common infections.
So, if your child falls into any of these categories, then any time a fever is present it has to be taken seriously—call your doctor.
However, for anyone else, the height of a fever doesn’t actually matter too much.
So what number should make you drop everything and go to the ER, no matter what time of day or night it is?
I notice a lot of jaws drop whenever I say this, but: the “drop everything and go to the ER at 2AM” number is 107°F.
Luckily, your child should never really get that high (I’ve only seen it once & it was bad). And yet, many common illnesses—including certain benign viruses, ear infections, strep, flu, and pneumonia—can give a child 105°F quite easily.
Why? Because their immune systems are 1). Quite strong, and 2). Seeing many germs for the first or second time. The result is that kids mount strong responses to infections—and thus big fevers.
Therefore, if fever is the main symptom, and your child isn’t under 3 months old or has any of those special medical conditions, then there is almost never any need to go to the ER at 2AM based on the height of the fever alone.
However, if we’re talking just numbers, I will usually say that if your child hits 104°F, she should probably be seen in the next 24 hours—because the higher a fever gets, the higher the odds that the infection is something we can treat, like strep throat, an ear infection, or pneumonia.
You should also know that the body’s temperature gets higher as the day goes on—so higher fevers usually come in the afternoon or evening.
This is why it’s important to wait a full 24 hours after the last fever before you decide that your child is better—a fever one night that’s gone the next morning might creep back up again by that second night.
WHAT MATTERS MORE THAN THE HEIGHT OF THE FEVER?
Ultimately, and this might be surprising to some, it isn’t the number itself that really matters.
If fever is the primary symptom, meaning that if either the worst part of the infection—or maybe even the only sign of an infection—is fever alone, then there are two things that matter more than how high it is:
1). Whether or not you can make the fever budge with medicine
Let’s say your child has a fever of 104.1°F. You might not bring that fever down to 98.6°F with medicine, and that’s okay. But if you can’t make it budge at all, if you try the things that we’re going to talk about in a few minutes and you can’t crack 104°F, then that’s a worry. That could be a sign of a more serious infection, and that’s worth getting checked out right away.
2). How many days the fever stays
When it comes to the number of days, remember the number ‘5.’ While the average cold for a child lasts between 15 and 25 days, most common colds won’t give you 5 or more days of fever.
So, if your child hasn’t been seen by a doctor yet but has had a fever for 4 or 5 days, go get checked out. Or, if your child has already been seen by a doctor but the fever has now stuck around to a 5th day, then you should give your pediatrician another call.
There are two reasons why 5 days is the cutoff:
- There are certain types of diseases that we have to start thinking about when a fever goes to 5 days or more. Maybe that infection we thought was just a cold at the first doctor’s visit isn’t actually a cold at all…but back when the fever had only been around for a day or two, a cold seemed like it was the most likely cause. Now that the fever’s been around for 5 days, we have to think differently.
- Sometimes the reason that a fever is sticking around for so long is that now the infection has progressed into something else—for example, maybe the fever was there at the start because your child had a cold, but now the fever is sticking around because that cold has led to a “secondary infection,” like an ear infection.
This second reason also touches on why we pediatricians sometimes suggest that a parent sit on a fever for a day or so to see what happens.
So often, we’ll get a phonecall from a parent saying: “Daycare just called and my 2-year-old has a fever—so I’m picking him up and coming straight to you!” But if a fever’s only been around for a couple of hours, there might not have been enough time for signs of what’s causing it to have blossomed. There might not be enough pus behind the ear for your doctor to notice an ear infection; or there might not be enough bacteria in the throat yet to get a positive strep test. So what ends up happening is that we’re left saying, “Everything looks okay right now, but if the fever sticks around, then come back.” Sometimes the infection just needs time to “declare itself.”
THE DOORWAY TEST
Let’s flesh out this idea of the number mattering less than we might think.
A moment ago, I wrote that if we were going to say what number should send you to the ER at 2 in the morning, I would say 107°F. And I know that that sounds insane!
But the thing is, besides how long it’s been around or whether or not you can make it budge, it’s not really the number itself that matters—instead, it’s what’s going on around that number, what’s going on around the fever, that really matters.
One of my mentors in medical school and residency was a doctor named Wolfgang Rennert, a wonderful pediatrician who grew up in Germany and practiced medicine for a long time in South Africa.
I remember him saying: “You American doctors are like John Wayne with your stethoscopes! You walk into a room and the first thing you do is reach for your stethoscope like you’re reaching for your pistol…No. What you need to do is examine the child from the door. And from the doorway, you can start to assess: ‘How sick is this child?’Is she happy and playing? Is he crying out in pain? Is she drowsy and confused?”
What’s going on around the fever can give you an idea of how much you really need to worry.
This isn’t just something for medical students and doctors. This is an approach that you can use, too.
WHEN TO CALL THE DOCTOR
Let’s talk about some of the things that can occur with or around a fever that should make you call your child’s doctor.
I’m going to break this down into 3 categories:
- When to go to the ER (not an urgent care**)
- When to call your doctor, no matter what time of day or night it is (in this category, if it takes your doc over an hour to respond, then you may want to go to the ER)
- When to get your child checked out within the next 24 hours
**Now before we dive in, I want to point out something that’s important. An “urgent care” isn’t really for something that’s “urgent”—especially when it comes to kids. An urgent care is for convenience only. If your pediatrician’s office is closed and you really don’t want to wait until the next day for a strep test or drops for pinkeye or swimmer’s ear, that’s what an urgent care is for. But for that is serious, for something that’s important enough for you to get checked out at 2AM, you need to go to an ER.
***I also want to note that this list isn’t exhaustive—so just because something isn’t on this list, doesn’t mean that it might not be important—so use your best judgement. These are just some of the most common problems that might be encountered with a fever in kids.
- CALL 911—If your child is burning up and is difficult to arouse. Of course, kids will often be drowsy with a fever, can feel crummy and sleep more than usual. But if your child has a fever and you really can’t awaken him, that’s an emergency.
- GO TO THE ER—If your child has a fever you can’t get your child to settle down and get comfortable, despite giving medication [see below], giving the medicine enough time to work (usually at least an hour), and trying other comfort measures.
- GO TO THE ER—If your child has a fever and has difficulty breathing. If your child has any of the signs of distress discussed HERE, get checked out immediately. With breathing, I also want to point out that kids will often breathe quickly with a fever—kind of like a puppy panting to blow off hot air—and that’s not necessarily a worry. But if you bring the temperature down with medicine and your child is still breathing faster than normal, then get checked out urgently—as this could be a sign of pneumonia, wheezing, or other potentially serious infections of the airway.
- GO TO THE ER—If your child has fever with a stiff neck or severe back pain. In this case, of course, we’re worrying about meningitis.
CALL YOUR PEDIATRICIAN IMMEDIATELY
- If your child has a fever and is limping or is refusing to walk. This could be a fairly benign process called transient synovitis, but it could be something worse, like a joint infection or a bone infection, so it’s worth getting looked at to make sure that’s not the case.
- Similar to this is fever with joint pain—worth calling about at any time of day or night, and possibly needs to get looked at quickly
- Fever with bruising—call at any time if your child has a fever and is suddenly developing what look like bruises despite only minor or no injuries.
- Fever with a seizure—Fevers can cause seizures at any temperature over 100.4, NOT just high temperatures. A seizure is usually marked by violent shaking of the body, and the child will not be responsive—she won’t interact with you while it’s happening. Chills, on the other hand, might cause your child to shake, but she’ll be able to talk to you through them. Luckily, febrile seizures are actually not harmful—they’re scary to watch, but don’t harm kids in any way. Even so, if your child experiences a seizure with a fever, call your doctor right away. Depending on the situation, she may want your child seen to make sure it was just a simple febrile seizure.
CALL YOUR PEDIATRICIAN WITHIN 24 HOURS
- If your child has fever with painful urination. This could very well be a urinary tract infection, and anyone who’s ever had a UTI knows that they’re really uncomfortable. Plus, the presence of a fever with a UTI can indicate that the infection is tracking up toward the kidneys, so it’s definitely worth getting checked out. Now if your child has fever, painful urination, plus back pain or vomiting—then get checked out more urgently.
- If your child has a fever with a new rash. Sometimes this can be something that is annoying but generally benign like hand-foot-and-mouth disease, or something treatable like strep throat, but there are also some very serious diseases that can cause a new rash to pop out with a fever, so it’s always worth calling about this.
- If a fever comes in the middle of an illness or after a first fever has been gone for over 24 hours. Fever at the start of a cold = usually part of the cold. Fever in the middle of a cold = new infection. For example, if your child had a runny nose for a week and *then* a fever came on a few days later, then this can be a sign of a secondary infection, so call your pediatrician within 24 hours of this happening. The same is true if a second fever comes up when a first fever has been gone for over 24 hours—when a fever is gone for over a full day, the first infection is usually improved, so a new fever could be a sign of a secondary infection. These secondary infections are usually just viruses—just a second cold—but they can be something potentially bacterial and treatable, like an ear infection or pneumonia. So, it’s usually worth an office visit.
HOW TO TREAT A FEVER
The first thing to think about is: “Do we need to treat the fever at all?”
As I said above, the fever is there to fight the infection. Plus, the height of the fever alone isn’t necessarily the thing to worry about, but rather what’s going on around the number and how long it’s been present.
What I usually tell my patients’ parents is that if their child is generally happy, can eat and drink and do the things she needs to do, then you don’t necessarily have to treat the fever at all.
So the ultimate rule with fevers is this:
“The reason to treat a fever is to make your child more comfortable.”
That’s it—that’s why we try to fix a fever—to make an uncomfortable child feel more comfortable.
Think about it—what happens when kids are uncomfortable? Not only does it break our hearts as parents, but they also don’t eat or drink well.
The not-eating part is less worrisome than the not-drinking part—even though it tends to drive any parent crazy to see our kids not eating! There’s a reason why no one can remember whether the old saying is “feed a fever, starve a flu” or “starve a fever, feed a flu.” And that’s because for most kids, missing out on food for a day or so doesn’t matter quite so much. What matters most is drinking. Probably the worst complication of the symptoms of fever alone is dehydration. When kids feel bad, they don’t drink—and that can make things worse.
So, my general recommendation with fevers is that you don’t necessarily need to treat the fever to bring the number down. What you need to do is treat a fever if your child is uncomfortable, and absolutely if she is getting close the point that she’s not drinking. If your child can tolerate the fever, if he can play and eat and drink and do his normal things, then you can let the fever be, watching instead for the duration of the fever and what symptoms go along with it.
Of course, odds are that most kids are going to feel really crummy when they have a fever. So, let’s talk about how to treat it and how to help them feel more comfortable.
The two categories of fever treatments are medication and non-medication. And to be honest, these approaches really work best when done together.
The non-medication approaches involve trying to bring the body’s temperature down by using something cool. For instance, you can put your child in a lukewarm bath. (Make sure that it’s not cold—lukewarm is perfect.) The lukewarm water helps to lower the body’s temperature. You can also take a cool washcloth and place it on your child’s forehead, his belly, or the back of his neck.
Of course, these measures only last for a little while, so that’s where medication comes in.
In the United States, the two medications that we use are acetaminophen—which has the brandname Tylenol—and ibuprofen—which is sold as the brand names Motrin and Advil.
The dosing for these medications is based on your child’s weight. Therefore, to find out the right dose, you have to have a rough idea of how much your child weighs. You’ll sometimes see dosing charts by age, but those aren’t as accurate. Think about it—a big 7-month-old who is 20 pounds is going to need more medicine than a 7-month-old who is only 14 pounds. Therefore, dosing charts that use age aren’t usually very accurate.
The other problem with many common medication charts is that they give you a dose for a range of weights—for example, “20-27 pounds get X dose, 28-34 pounds get Y dose.” This usually ends up with kids at the upper end of the weight range getting underdosed—why would a 27-pound child get a radically different dose than a 28-pound child?
The result of this second problem is that parents who follow these charts are often left wondering why the medicine isn’t working. The reason? The child on the upper end of that weight range is probably getting the wrong dose.
That’s why I’ve created an exact dosing chart for Acetaminophen, Ibuprofen, and even Benadryl for every single weight up to 100 pounds—and I’ve made it free for you to have and use whenever you need it. Download it in the blue bar at the bottom of this article, then print it out or keep it on your phone so you always have access to it (i.e., on iPhones, tap “Open in iBooks”).
HOW TO PROPERLY GIVE THE MEDICINE
If your child has a hard time taking medicine, be sure to check out my article on “How to Get Your Child to Take Medicine.”
Acetaminophen (Tylenol) can be given every 4 hours if you need to. Ibuprofen (Motrin, Advil) can be given every 6 hours. So, Ibuprofen is a nice one to give before bed because it lasts longer.
Now sometimes, when a fever hits 103 or higher, it might be difficult to bring it down with just ibuprofen or Tylenol. You can actually use both—they work in different ways, so the side effects don’t add up, but the benefits do. One nice way to do it (if you have a stubborn fever) is to give each medicine every 6 hours, but overlap so that you end up giving one or the other every 3 hours. For example, if you give Tylenol at 12 & 6, then you can give ibuprofen at 3 & 9. That’s the shortest, regular interval at which you can give something—otherwise, you’re waiting 4 hours for Tylenol, or 6 hours for ibuprofen.
In terms of side effects, both Tylenol and ibuprofen are usually fairly safe when given at the right doses. However, Tylenol can cause severe liver damage if overdosed, so you always have to be careful to give the right amount—it’s better to underestimate your child’s weight and dose than to overestimate. With ibuprofen, it’s processed by the kidneys, which don’t mature well enough until at least 6 months of age, so no babies younger than 6 months should get ibuprofen. If given routinely for several days, ibuprofen can irritate the lining of the stomach. So, if you have to give it for more than a day, try to give it with food or something in your child’s stomach to reduce the odds of that irritation developing.
THE FEVER MAY COME BACK WHEN THE MEDICINE WEARS OFF
This is something that worries parents all the time, but is totally expected. When you give Tylenol or Ibuprofen, the medicine isn’t fixing the cause of the fever—the infection—but rather blocking the body’s chemicals that create the fever. Once the medicine wears off, because the infection is still there, the fever might come back.
If medication brings the fever down, that’s a good thing. If the fever comes back after the medications wear off, then it simply means that your child is still actively infected. This is when you need to watch how long the fever lasts, getting in touch with your doctor again if the fever approaches 5 days, other issues come up, or your doctor has instructed you to reach out.
WHEN IS YOUR CHILD BETTER/NOT CONTAGIOUS?
This is the big question, right? How do you know when your child is better, and when can she see other kids again?
The rough answer to both of those questions is “24 hours after the last fever.”
The reason I say “rough” answer is that when it comes to being contagious, there are other factors that could be at play. For example, with strep throat, your child might no longer have a fever, but if he hasn’t been treated with antibiotics then he’s still contagious. Other illnesses are slightly contagious for long after a fever as well. Viral pinkeye, for example, can technically be contagious for up to three weeks! So if viral pinkeye was part of your child’s cold, then she’s technically contagious for a while after the fever is gone. However, no pediatrician will tell you to keep your child sequestered for three weeks—so for most illnesses, we’ll tend to say that kids are most contagious through 24 hours after the last fever. Talk to your pediatrician about your child’s particular illness for a personalized answer.
Why do we say 24 hours after the last fever?
Remember from above when I said that the body’s temperature gets higher as the day goes on. The highest fever will usually come in the afternoon or evening. SO, if your child had a fever last night, but wakes up without a fever, you can’t send her to school! Not having a fever in the morning doesn’t mean too much—instead, if there is no more fever that next night, then you are more likely in the clear.
This is an issue that comes up all the time—parents send their kids to school or daycare only to get a call at 11am to pick the child back up. Avoid this issue in the first place by waiting to see if the fever returns in the afternoon or evening, and you’ll keep both your kids and their classmates healthier.
This article has certainly not been a 2-minute read(!), but I’ve tried to cover everything that you’ll ever need to know about fevers as a parent. I hope that you now have the insight you need to help your child—and yourself—feel better.
Again, while this is the same information I would tell my own patients, you know your child and instincts best—if you ever have any concerns at all about your child’s health, please contact your pediatrician.
Dr. Steve Silvestro is a pediatrician, dad, and host of The Child Repair Guide Podcast, which brings insights from the world’s best experts on parenting and kids’ health directly to parents. Contact him for media and speaking engagements here.