The best thermometer for measuring fever in a child is….

The Pediatric Insider

© 2013 Roy Benaroch, MD

There are lots of choices, so which one is best? Which kind of thermometer should parents buy and use?

Keep in mind that body temperature is one measurement—but it’s certainly not the only measurement, and it’s far from the most important way of knowing if your child is ill. Kids can be seriously sick without a fever; and almost all ordinary children with fever do not have a serious illness. There’s far too much “fever phobia” out there, and there’s already far too much preoccupation with whether Junior has a fever and how high the temperature is. Fever itself doesn’t hurt anyone. It doesn’t cause any damage, and won’t hurt your child. But fever can make your child feel sick, so it’s worthwhile to treat it. Safe medicines for fever can help your child feel more comfortable.

Also, any discussion of fever needs a caveat: all of this information is only for healthy, otherwise-well children with no immune-compromising condition. That means children who have NOT gotten all of their vaccines are NOT healthy and otherwise-well, and have a much greater risk of serious, even overwhelming infection. If your child isn’t up to date on vaccines, I offer no advice on how to measure or handle temperatures. Call your doctor. Better yet, unless there is a medical contraindication, get your child caught up on vaccines, pronto. You wouldn’t drive without your child in a safety seat, would you?

Another fun fever fact, before we get to the meaty stuff: if anyone has told you that 98.6 F is the “normal” temperature, they’re wrong. It’s not normal, it’s average. 98.6 is no more the normal than saying 5’10” is the normal male height. As with every other measurement in nature, temperatures vary among individuals, and temperatures vary throughout the day. 98.6 is the average, meaning that normal ranges from below this to above this. In most circumstances, most pediatricians consider anything measured at 100.4 or above to be a fever. Values measured below that threshold are not “low grade fevers”—they’re normal temperatures. And don’t start adding degrees, depending on how you measured the temp. That just confuses everyone.

So what are the choices for thermometers, and which should you choose? I’m going to include links here to Amazon products, just so you know what I’m talking about. (I have no financial relationship, and I don’t care if you buy through these links, etc.)

Mom or dad’s hands: These actually make a reasonably good thermometer, at least for “ruling out” fever. If you touch your children, and they do NOT feel warm, they almost certainly do not have a fever. The inverse of this, by the way, is not true: often your child will feel warm, and won’t actually have a fever—so touch can rule out fever, but cannot confirm or measure a fever. But it’s a start, and for busy people with older, healthy kids, using your hands alone is not an unreasonable way to check.

Rectal thermometer: These work, though they’re slow. They’re also the only method used in most studies of small babies less than 2-3 months of age, so typically that’s what pediatricians want you to use at that age. But please, no rectal temps in older kids, OK? It’s just creepy and unnecessary.

Axillary thermometer, AKA “The Chicken Wing”: These work, though they’re also kind of slow. Not bad for an estimate. Kids feel silly sitting there holding their arms still, but that’s the price they have to pay.

Oral thermometer: Those old, mercury-filled ones you have to shake back down have gone the way of the dinosaurs. They’re all digital now, and they read faster. And if you shake one down after reading it people will edge away from you and give you odd looks. These work about as well as the others in this list.

So far, rectal/axillary/oral, it’s all good, at least when they’re appropriate for the age. But they’re all old school. Isn’t there something newer that’s better?

Binky-temps (AKA: a digital thermometer built into a pacifier): Please. This measures, maybe, the temperature of the top of the tongue, wherever that’s been lately. Don’t waste your money.

Forehead tape thermometers: These have vague glowing numbers that indicate, well, where the vague glowing numbers are. Might as well make up a temperature rather than rely on these things.

Infrared thermometers: The ones marketed to parents are sometimes called “non-contact” thermometers, because these don’t actually touch your child. They’re also sold at hardware stores to measure the surface temps of things from quite a long way away, like industrial transformers or crème brulee. They are not suitable for people-use, because they only measure surface temperature. We want core temperature, or the temperature of the blood as it exits the chest. The temperature of the skin is NOT an acceptable or accurate way to measure core temps.

Forehead thermometers:  One company sells a digital version of what’s essentially your hand, touching your child’s forehead. Use your own appendages instead, they’ll be just as accurate, and they’re much more handy! (Get it? Handy?! Hahahahaha. Hem. Sorry.)

Ear thermometers: Supposedly these measure the temperature in the middle ear, where the monkeys live (or so I’ve been told.) Several years ago, a company that will remain nameless (hint: the name rhymes with mermo-flan) gave my practice a dozen or so of these, so we could try them out. I guess they figured we’d love them, and patients would see us using them, and they’d rush out and buy them too. Trouble is, the darn things were terrible—they missed high temps, they inflated no-temps, they gave children random fevers. So we threw them all away. If you’ve already bought one, maybe you can repurpose it as a chicken cutlet pounder or decorative paperweight.

Temporal artery thermometer: I’ve save the best for last! It’s quick, it’s easy, and a recent study showed that it’s pretty much as good as a rectal temp.

So: if your child feels warm, and you’d like to measure the temp, a temporal artery thermometer may be the best way to go. They’re more expensive than an ordinary digital thermometer for oral or axillary use, but they’re faster and I think they’re easier to use.

We have a winner!

More about fevers:

The fever action plan

Why do people get fevers?

Medicines for treating fever

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6 Comments on “The best thermometer for measuring fever in a child is….”

  1. adc Says:

    Your comment that children who have not received all their vaccines are not healthy or otherwise well pretty much guarantees I will never read another one of your posts again. You say you can’t offer advice on behalf of those kids who may have a fever? Ridiculous. Good riddance.

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  2. Dr. Roy Says:

    adc, unvaccinated children are at dramatically increased risk for serious or deadly infections that may present as fever. This was an (obviously) lighthearted post about choosing thermometers for low-risk, healthy children. Children who have immune deficiencies, other health conditions that increase their risk of serious infections (such as sickle cell anemia, cancer, neutropenia, or those on immune-compromising medications), or children who have not received routine vaccinations should follow very specific instructions from their health care provider, who knows their individual child best, about the best way to measure and deal with fevers.

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  3. lilady Says:

    Thanks for another excellent article about fevers and thermometers.

    My child was born with a rare genetic disorder. He was immune deficient and had a bleeding disorder (pancytopenia), along with a partially controlled grand mal seizure disorder.

    It was important to have an accurate measure of his core body temperature to prevent dehydration and to decrease the chance of an internal bleed, that occurred with the destruction of platelets from high fevers.

    Yes, I still have a bunch of rectal thermometers…eight years after his death. During his lifetime, we depended on the benefits of herd immunity and parents not “hiding in the herd”.

    BTW, I am a recently retired public health nurse/clinician-epidemiologist and I know only too well the risks associated with parents who “opt out” of vaccines that prevent serious, sometimes deadly, vaccine-preventable-diseases.

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  4. Dr. Roy Says:

    lilady, thanks for your comments, and I am sorry about your son. You’ve illustrated how important it is for all of us, children and parents, to be vaccinated– to protect those of us who are depending on their community. Some children cannot be safely vaccinated, and they’re counting on all of us to protect them.

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  5. sm Says:

    It was good until you said choosing to be judicious about when & how many attenuated viruses to introduce to a developing immune system was the equivalent to unhealthy. Of course delayed or non-immunization creates higher risk of serious illness. I also read multiple abstracts about the recent MMRV combo. It is all risk assessment either route you go. Immunization schedules are designed around lowest common denominator. Double studies aren’t done on combination shots. We aren’t all idiots that try to actually be educated about what is being given to our children.
    Yes, you should say those who don’t immunize need to be much more cautious with fevers. That would be a wise disclaimer. Why not just say that instead of being condescending. Unhealthy is unhealthy. Non-vaccinated is non-vaccinated. To be clear, I have 3 children all of which are vaccinate against the “significant diseases” as we consult with our pediatrician. We didn’t do it on the newest 2, 4, 6 schedule. We didn’t do Roto or Hep B in the hospital. Are our children unhealthy? Right now maybe they aren’t, but what if next year the AMA decides they should be standard. Then they are on the “list” and our kids become unhealthy. I get it.
    Was it really “obviously” light- hearted when you made the car seat joke? You are so obviously hilarious and not covering up any intense bias.

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  6. sm Says:

    *double blind studies that is.

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