Fever in Children: When to Worry and What to Do
Fever is the number-one reason parents call the pediatrician and visit the emergency department — and it is also one of the most misunderstood symptoms in pediatrics. Here is what actually matters, from a pediatric emergency medicine physician.
Key takeaways
- A fever is 100.4°F (38°C) or higher — and how your child looks and acts matters more than the number.
- Babies under 3 months old with a fever need the emergency department immediately, every time.
- Treat for comfort, not a perfect temperature: offer fluids, dress lightly, and use weight-based fever reducers if your child is uncomfortable.
- Never use cold baths, rubbing alcohol, or aspirin for a child's fever.
What counts as a fever in a child?
A fever is a body temperature of 100.4°F (38°C) or higher. That number is the same for babies, toddlers, and big kids. A temperature of 99.5°F is not technically a fever, even if your child feels warm to you.
It helps to remember why fever happens: it is your child's immune system doing its job. Raising the body's temperature is one way the body fights infection. Fever itself is a symptom, not a disease — the real question is always what is causing it and how your child looks and acts.
How should I take my child's temperature?
Not all thermometers are equal:
- Rectal (in the bottom) is the most accurate method for babies and toddlers under 3, and it is what doctors rely on for infants.
- Temporal artery (forehead swipe) thermometers are reasonable for quick screening in older babies and children.
- Underarm (axillary) readings run low and are the least reliable — fine for a rough check, but confirm an important reading another way.
- Oral works for children old enough to hold the thermometer under the tongue (usually age 4 and up).
Always follow your thermometer's instructions, and use the same method when you recheck so you can compare readings.
How can I help my child feel better with a fever?
The goal of treating a fever is comfort, not a perfect number on the thermometer. If your child is drinking, playing, and resting reasonably well, you do not need to chase the temperature down to normal.
- Offer plenty of fluids. Fever increases fluid needs. Water, breast milk, formula, or oral rehydration solution are all good choices.
- Dress lightly. One light layer is enough — do not bundle up a feverish child, which traps heat.
- Let them rest, but do not force bed rest if they feel like quiet play.
- Fever reducers for comfort: acetaminophen (Tylenol) or ibuprofen (Motrin/Advil) can ease aches and crankiness. They do not treat the underlying illness. See our medication dosing guide for weight-based dosing — and never give ibuprofen to a baby under 6 months old.
Avoid these
- Cold baths or ice water — they cause shivering, which raises body temperature.
- Rubbing alcohol on the skin — it can be absorbed and is dangerous.
- Aspirin — never give aspirin to children; it is linked to Reye syndrome, a rare but serious illness.
Fever myths vs. facts
Myth: Teething causes high fever.
Fact: Teething may cause fussiness and a slightly raised
temperature, but true fever (100.4°F+) is not caused by teething. Look for another cause.
Myth: The higher the fever, the more serious the illness.
Fact: How your child looks and
acts matters far more than the number. A playful child with 103°F from a cold is less concerning than a
lethargic, hard-to-wake child with 101°F.
Myth: Fever can cause brain damage.
Fact: Ordinary fevers from infection do not cause brain
damage. Only extremely high body temperatures above about 107–108°F — which essentially never happen from
infection — can harm the brain.
Myth: You must bring every fever down to normal.
Fact: Treating for comfort is enough.
A child who is comfortable does not need medicine just to normalize the thermometer.
Myth: “Feed a cold, starve a fever.”
Fact: Children with fever need fluids and
nutrition. Offer food as appetite allows — no starving required.
When should I call the pediatrician about a fever?
- Fever lasting more than 3 days
- Your child is not drinking well or has very little urine output
- Fever that went away for more than 24 hours and then returned
- Your child has a chronic medical condition or a weakened immune system
- You are simply worried — parental instinct counts
When should I take my child to the ER for a fever?
- Any baby under 3 months old with a rectal temperature of 100.4°F (38°C) or higher — go to the emergency department immediately, every time, no exceptions.
- Difficulty breathing, persistent vomiting, or signs of dehydration
- Unusually sleepy, limp, hard to wake, or inconsolable crying
- Stiff neck, severe headache, or a rash that does not fade when pressed (see our rash guide)
- A seizure with the fever
- Fever after a recent immunization in a baby under 3 months
Related reading: febrile seizure first aid, your 2 AM fever action plan, and 7 fever myths even experienced parents believe.
Sources
This guide was reviewed against guidance from:
Frequently asked questions
What temperature is considered a fever in a child?
100.4°F (38°C) or higher, measured with a thermometer. Feeling warm to the touch is not enough to confirm a fever.
Should I wake my sleeping child to give fever medicine?
No. If your child is sleeping comfortably, let them sleep. Treat fever for comfort — a comfortable sleeping child does not need to be woken for medicine.
Can I alternate Tylenol and Motrin for my child's fever?
Some pediatricians recommend alternating, but it is easy to make a dosing error. Do not alternate on your own — ask your pediatrician first, write down every dose and time, and see our dosing guide.
My child feels hot but the thermometer says 99.9°F. Is that a fever?
No — 99.9°F is below the 100.4°F threshold. Recheck later, and pay more attention to how your child is acting than to a borderline number.
How long does a viral fever usually last?
Most fevers from common viral illnesses last 2–3 days. Call your pediatrician if a fever lasts more than 3 days, or sooner if you are worried.
Reviewed by Ali Ozcan, MD, MBA
Board-certified pediatric emergency medicine physician and creator of ER4Kids. This guide reflects the same trusted, evidence-based guidance Dr. Ozcan provides to families in the emergency department.
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