What temperature counts as a fever?

100.4°F (38°C) is the standard threshold. Under three months that number alone means a same-day call. Above that age it is the start of a conversation about how the child looks, not a verdict on its own.

Does teething cause fever?

No. Pediatricians are clear on this — teething doesn't cause a real fever or diarrhoea. If a child is genuinely hot, treat it as illness rather than attributing it to teeth.

Should I wake a sleeping child to give fever medicine?

Generally no. Fever reducers are for comfort, and sleep is doing more good than a lower number would. The exception is if a doctor has told you otherwise for a specific reason.

Can I alternate paracetamol and ibuprofen?

Ask your pediatrician before doing this rather than starting it yourself. Alternating raises the chance of a dosing error at 3am, which is the actual risk in most households.

When it happens · 6 min read

Your child has a fever: what the number actually means

It is almost always the middle of the night, and the first thing anyone does is reach for the thermometer and then decide how frightened to be based on the number it gives back. That is the wrong instrument to be reading.

A fever is not the illness. It is the immune system raising the thermostat on purpose, and the American Academy of Pediatrics is explicit that not every fever needs to be treated. What matters is the child attached to the temperature — and there is exactly one age where that stops being true and the number alone decides.

Last updated August 3, 2026

Read the child, not the thermometer

A baby who is drinking, producing wet nappies, and can be settled at 102°F is in better shape than a listless one at 100.8°F. Alertness, fluids, and whether they can be comforted are the signals worth watching; the digit is a poor proxy for all three.

This is why "how high is too high" has no clean answer above the newborn period. The AAP's framing is that fever is a symptom and a defence, not a disease to be driven down to a target. Treating is for comfort — a child who is miserable, or who won't drink because they feel awful — not for the reading itself.

Fever also does not, on its own, tell you bacterial from viral, or serious from trivial. Most fevers in an otherwise well child are viral and self-limiting. The pattern that matters is the trajectory: a child who was improving and then clearly got worse again is worth a call, whatever the number is doing.

Under three months: the one hard line

This is the exception to everything above. In a baby under three months, a rectal temperature of 100.4°F (38°C) is a same-day call, every time — not a "let's see how they are in the morning". A very young immune system gives fewer outward signs, so the usual reassurances don't apply.

Do not give a fever reducer first to watch whether it comes down. Under three months, fever reducers shouldn't be given unless your pediatrician tells you to, and dosing beforehand erases the information they need to make a decision.

A handful of things skip the phone call and go straight to emergency care at any age: pauses in breathing, rhythmic grunting with each breath, nostrils flaring, or skin, lips or nails that look pale, grey or blue.

Skip the cooling folklore

The AAP no longer recommends alcohol baths, ice packs, or cold sponging. They cause shivering, which raises body temperature rather than lowering it, and alcohol can be absorbed through the skin.

Lukewarm — not cold — is the only bathing that helps, and mostly it helps because it is pleasant. Fluids and a lighter layer do more than anything applied to the outside of a child.

Febrile seizures, said out loud

This is the fear underneath the 2am thermometer check and almost nobody names it, so: about three to four children in every hundred have a febrile seizure, between six months and five years old, most often right around 12 to 18 months.

They are terrifying to watch and they are not brain damage, not epilepsy, and not caused by letting a fever go untreated. Treating a fever does not prevent them.

What to do: put them on their side somewhere they can't fall or hit anything, don't put anything in their mouth, and time it. A first seizure warrants medical assessment — call, and call emergency services if it runs past five minutes.

When to make the call

Under three months and 100.4°F rectal: same day, always.

At any age: fever past five days; breathing that looks like work; signs of dehydration; a child who was getting better and then clearly got worse; a fever with a rash that doesn't fade under pressure; or a first febrile seizure.

And the one that isn't on any list but is the most reliable of all: a child who simply doesn't seem right to the person who knows them best. That instinct outperforms the thermometer, and it is a legitimate reason to call.

Common questions

What temperature counts as a fever?: 100.4°F (38°C) is the standard threshold. Under three months that number alone means a same-day call. Above that age it is the start of a conversation about how the child looks, not a verdict on its own.
Does teething cause fever?: No. Pediatricians are clear on this — teething doesn't cause a real fever or diarrhoea. If a child is genuinely hot, treat it as illness rather than attributing it to teeth.
Should I wake a sleeping child to give fever medicine?: Generally no. Fever reducers are for comfort, and sleep is doing more good than a lower number would. The exception is if a doctor has told you otherwise for a specific reason.
Can I alternate paracetamol and ibuprofen?: Ask your pediatrician before doing this rather than starting it yourself. Alternating raises the chance of a dosing error at 3am, which is the actual risk in most households.

Written from the same sources we cite everywhere else, and it is not a substitute for your own doctor. If something feels wrong to you, that instinct is a good enough reason to call — you know this child better than any page does.