Fever in children: what the number means, when to worry, and what to do
Last updated September 3, 2026.
Fever is your child's immune system doing its job, and how your child is acting tells you more than the number on the thermometer. A fever is 38C (100.4F) or higher. Most childhood fevers come from ordinary viral infections and settle within a few days with fluids and comfort. The things that matter: your child's age, their behavior, and a short list of specific red flags.
The checks that actually matter
Watch the child, not the thermometer. The reassuring picture: they are drinking, having wet nappies or trips to the toilet at roughly normal frequency, responding to you, smiling or playing at least a little between miserable patches, and their breathing is normal. The concerning picture: listless, floppy, or unusually drowsy; not drinking and producing far fewer wet nappies; breathing fast, hard, or with grunting; inconsolable crying or a high-pitched cry; or a rash that does not fade when you press a glass against it (the glass test: press a clear glass firmly on the rash, and if the spots do not blanch, treat it as an emergency).
What actually helps?
- Fluids, little and often: water, diluted squash, breast milk or formula for babies, in frequent small amounts. Dehydration is the main thing home care prevents, and wet nappies are the gauge.
- Comfortable, not bundled: dress them in light clothing and keep the room at a comfortable temperature. Do not pile on blankets to sweat it out, and do not sponge with cold water; both work against the body's regulation.
- Medicine for distress, not for the number: paracetamol or ibuprofen (dosed by weight from the packet) if they are miserable or in pain. You do not need to give medicine for a feverish but happy child, and you cannot and need not bring the temperature to normal. Never give aspirin to under-16s.
- Rest and quiet: let them sleep; fever is metabolically exhausting. Keep them home from school or nursery while the fever lasts.
- Know your age lines: any baby under 3 months with a temperature of 38C or higher needs same-day medical assessment, always. From 3 to 6 months, 39C or higher, or any fever with an unwell baby, needs same-day advice.
When is it an emergency?
Call emergency services (999/911/112) for: a non-blanching rash on the glass test, severe difficulty breathing, a fit lasting more than 5 minutes (or a first-ever febrile convulsion), unresponsiveness or a floppy, hard-to-wake child, or a bulging soft spot with a tense cry. Same-day urgent care for: fever lasting more than 5 days, signs of dehydration (very few wet nappies, no tears, dry mouth), ear or throat pain that is severe, or a fever that keeps coming back. Trust your gut: you know your child, and "something is not right" is a legitimate reason to be seen. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
What a Pymander AI doctor consult looks like
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Common questions
What temperature counts as a fever in a child?
38C (100.4F) or higher is a fever. The exact number beyond that matters less than parents fear: a happy, drinking child at 39.5C is less worrying than a listless one at 38.5C. What changes with the number is mostly your monitoring intensity. The hard age rules: under 3 months, 38C or more is always a same-day medical review; 3 to 6 months, 39C or more, or any fever with an unwell baby, gets same-day advice.
When should I take my child to the doctor for a fever?
Same-day for: any baby under 3 months at 38C+, fever lasting more than 5 days, signs of dehydration (few wet nappies, dry mouth, no tears), severe ear or throat pain, a fever that keeps recurring, or your parental instinct saying something is off. Emergency services for: a rash that does not fade under a glass, labored or very fast breathing, a floppy or hard-to-wake child, a seizure lasting over 5 minutes, or unresponsiveness. In between: a child who is drinking, responsive, and has playful moments can be watched at home.
Should I give medicine for every fever?
No. Paracetamol and ibuprofen are for comfort, not for normalizing the temperature. A feverish child who is playing does not need medicating; the fever itself is part of the immune response and not harmful at ordinary levels. Give medicine when they are miserable, in pain, or refusing to drink, dosed by weight from the packet. You can use either one; combining or alternating them is not routinely recommended. Never give aspirin to anyone under 16 because of Reye's syndrome.
What are febrile seizures, and are they dangerous?
Febrile seizures are fits triggered by a rising fever in roughly 1 in 20 children between 6 months and 6 years: the child stiffens or shakes, may go blue briefly, and is drowsy afterward. They are terrifying to watch and, in the simple form (under 5 minutes, whole body, quick recovery), do not damage the brain or mean epilepsy. During one: lay the child on their side, clear hazards, time it, and do not put anything in their mouth. Call an ambulance for a first seizure or one lasting over 5 minutes.
Can teething cause a fever?
Teething causes dribbling, chewing, fussiness, and slightly warm cheeks, but it does not cause a genuine fever of 38C or more. A true fever in a teething-age baby means an infection, not teeth, and attributing 39C to teething is a classic way real illnesses get missed. Teething coincides with the age when babies start catching everything, which keeps the myth alive.
How do I bring my child's fever down?
Fluids little and often, light clothing, a comfortably cool (not cold) room, and paracetamol or ibuprofen if they are distressed. What not to do: no cold baths or sponging (it causes shivering, which raises core temperature), no bundling to sweat it out, no alcohol rubs ever, and no waking them on a schedule just to check. Let them sleep; their behavior when awake is the real gauge, not the number.
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