Originally published February 2018. Reviewed and updated August 2026 to follow current American Academy of Pediatrics guidance.

Let’s start here: fever is not the enemy.

Fever isn’t an illness. It’s your child’s immune system doing its job — raising body temperature slows bacteria and viruses down and revs up the cells that fight them. There’s no evidence that fever itself damages a child or causes lasting harm.

So the goal isn’t a normal thermometer reading. The goal is a comfortable child. Treat the child, not the number.

What counts as a fever

100.4°F (38°C) or higher. At or above — 100.4 itself counts.

How to take it

• Under 3 months: rectal only. This is the one age where the exact number changes what happens next.
• 3 months to 3 years: rectal is most accurate; forehead (temporal artery) or armpit acceptable.
• 4 years and up: under the tongue is fine.

Ear thermometers aren’t reliable under 6 months — the canal is too narrow. Forehead thermometers are better than their reputation. Armpit is the least accurate and is a screening check only: if an armpit reading is near 100.4 in a baby, recheck rectally before acting on it. Skip mercury thermometers, pacifier thermometers and forehead strips.

Go now — ER or 911

• Any baby under 3 months with a temperature of 100.4°F or higher, taken rectally. Not negotiable, and not a video visit. A fever you measured at home still counts even if it’s gone by the time you arrive. The reverse is also true: a baby under 3 months who is unusually cold, floppy or not feeding needs to be seen even without a fever.
• A rash that doesn’t fade when you press on it. Press a clear drinking glass against the spots. If they blanch and disappear, that’s reassuring. If flat purple or red pinpoints stay visible through the glass, go now. This is the rash that matters.
• Your child is limp, won’t wake properly, won’t make eye contact, or cries inconsolably and nothing helps. How your child acts outranks any number on any thermometer.
• Trouble breathing — fast or labored breathing, grunting, flaring nostrils, ribs pulling in, or pauses.
• Stiff neck, severe headache, or bothered by light. In a baby: a bulging or tense soft spot, a high-pitched cry, arching, or refusing to feed.
• A seizure.
• Pale, grey, mottled or bluish skin, or cold hands and feet with a hot trunk.
• Signs of dehydration — no wet diaper in 8 hours, no tears, dry mouth, sunken eyes or soft spot.
• Fever in a child with a serious condition — sickle cell disease, cancer or chemotherapy, no spleen, a transplant, a central line or shunt, immune-suppressing medication, or significant heart disease. For these children fever is an emergency, not a wait-and-see.
• Fever after a hot car or extreme heat. That’s heat stroke — a different emergency.

Call us

• Any fever in a child under 2 years lasting more than 24 hours.
• Fever in a child 2 or older lasting more than 3 days.
• Temperature repeatedly climbing above 104°F.
• Your child still seems sick once the fever comes down.
• Severe ear pain, severe sore throat, or repeated vomiting or diarrhea.
• Recent international travel.
• Anything that worries you.

And as I always say: follow your gut. If something feels wrong, call — parent instinct is real information and we’d rather hear from you. One caution, though: it only works in one direction. A gut feeling that something is wrong is always a good reason to call. A gut feeling that everything is fine doesn’t override the under-3-months rule.

Treating the fever

You’re treating discomfort, not the reading. If your child is drinking, playing between doses and reasonably content at 103°F, medicine is optional.

• Acetaminophen (Tylenol) — from 3 months; under 3 months only if we’ve examined your baby and told you to. Works in 30–60 minutes.
• Ibuprofen (Motrin, Advil) — 6 months and older only. Skip it if your child is dehydrated or barely drinking; ibuprofen is hard on the kidneys when fluids are low.
• Never aspirin — not for any child or teenager with a viral illness. It’s linked to Reye syndrome, which attacks the liver and brain and can be fatal. Check labels for “salicylate” — that includes Pepto-Bismol.

The dosing points that actually cause emergency visits:

• Dose by your child’s weight, not their age. Ask us or your pharmacist for the exact dose and write it on the box.
• Use only the syringe or cup that came with that bottle. Concentrations differ between products, and a kitchen spoon is not a measurement.
• Don’t give cough-and-cold combination products — many already contain acetaminophen, and doubling up is the most common way children are accidentally overdosed.
• Don’t routinely alternate Tylenol and Motrin. There isn’t good evidence it makes children feel better, and juggling two drugs on two schedules at 3 a.m. is how dosing errors happen. If we’ve specifically told you to alternate for your child, follow that plan.

What not to do: no alcohol baths (alcohol absorbs through the skin and can cause dangerously low blood sugar), no ice packs, no cold or sponge baths — shivering drives the temperature back up. Don’t bundle a feverish child; one light layer. And don’t worry about food — fluids matter far more, and a day or two of poor eating with good drinking is fine.

Febrile seizures — because this is what you’re really afraid of

Two to five out of every 100 children will have one, usually between 6 months and 5 years. They are terrifying to watch and almost always harmless. Children who have simple febrile seizures show no drop in IQ, no learning problems and no brain damage, and their risk of developing epilepsy is about the same as any other child’s.

And this matters: fever medicine does not prevent them. Giving Tylenol earlier, or around the clock, doesn’t work — this has been studied. If your child has one, it isn’t because you missed a dose. Please let that guilt go.

If it happens: turn your child on their side on a safe flat surface. Nothing in the mouth, ever. Don’t hold them down. Move furniture out of the way. Look at the clock. Stay with them.

Call 911 if the seizure lasts more than 5 minutes, if breathing is hard or your child turns blue, if it happens again within 24 hours, or if your child doesn’t return to normal afterward. Any first febrile seizure should be seen the same day — a seizure with fever can occasionally be the first sign of meningitis.

After hours

Kids don’t get sick until after 5 p.m. on a Friday. For a child over 3 months who is alert and drinking, a virtual visit is a good way to get dosing help and work out whether this needs tonight or tomorrow.

Don’t use a video visit for: any baby under 3 months with a fever; a rash that doesn’t blanch; a child who is limp, unwakeable or inconsolable; trouble breathing; signs of dehydration; a seizure; a stiff neck; or fever in a child with sickle cell disease, cancer, no spleen or a suppressed immune system. Those need hands-on evaluation — go to the ER.

But if you read nothing else, read this: fever is not the enemy. Watch your child, not the thermometer.

As always, I hope you stay happy and healthy.

Carolyn Clark, NP-C

General education, not medical advice for your specific child. When in doubt, call us at (417) 332-3639.