Pediatric Fever (Fever in Babies and Children)

What fever is

The brain's thermostat (in the hypothalamus) raises the body's set point in response to infection. A higher temperature helps the immune system fight germs. Normal temperature varies through the day, from about 36.1 to 37.8 °C (97 to 100 °F).

Taking your child's temperature

Armpit readings run lower; confirm a borderline armpit reading rectally in young babies. Feeling the forehead is not reliable.

Common causes

• Viral infections: colds, flu, RSV, COVID-19, roseola, hand, foot and mouth disease, gastroenteritis. Most fevers in children are viral.
• Ear infections (otitis media)
• Strep throat
• Urinary tract infections: a common hidden cause of fever in babies and toddlers, often without obvious urinary symptoms
• Pneumonia and bronchiolitis
• Vaccinations: low-grade fever for a day or two
• Less common but serious: meningitis, sepsis, bone and joint infections, Kawasaki disease

Teething does not cause a true fever; at most it causes a slight temperature rise.

Why age matters

• Under 3 months: a baby's immune system is immature, and serious bacterial infections (urinary, bloodstream, meningitis) can look mild at first. Babies this age with fever are usually examined urgently, often with blood, urine and sometimes spinal fluid tests.
• 3 to 36 months: most fevers are viral, but doctors look carefully for urinary infections, ear infections and pneumonia.
• Over 3 years: children can usually describe symptoms, and how they look and behave is the best guide.

How high is too high?

The fever number alone does not show how serious the illness is. A child with 40 °C (104 °F) who is playing and drinking may be less sick than a child with 38.5 °C (101.3 °F) who is lethargic. Fevers from infection rarely go above 41 °C (105.8 °F) and do not cause brain damage. Heatstroke, which is different, can.

Febrile seizures

About 2 to 5% of children aged 6 months to 5 years have a seizure with fever. Most last under 5 minutes and cause no lasting harm. Lay the child on their side on a safe surface, do not put anything in their mouth, time the seizure, and call 911 or your local emergency number if it lasts more than 5 minutes or the child has trouble breathing. A first febrile seizure should always be assessed by a doctor. Fever medicines do not prevent febrile seizures. See seizures for more.

How to care for a child with fever

Comfort and fluids

• offer frequent fluids: breast milk or formula for babies, water and oral rehydration solution for older children
• dress in light clothing and use a light blanket
• let them rest; they do not need to stay in bed if they feel like playing
• lukewarm sponging is not recommended to bring down fever; never use cold water or alcohol rubs

Fever medicines

• Acetaminophen (paracetamol): can be used from 2 to 3 months; for babies under 3 months, talk to a doctor before giving any medicine.
• Ibuprofen: from 6 months of age, if the child is drinking well.
• Give the dose based on your child's weight, using the syringe or cup that comes with the medicine. Follow the label dose and maximum doses a day.
• The aim is comfort, not a normal temperature.
• Do not give aspirin to anyone under 18 because of the risk of Reye syndrome.
• Avoid routinely alternating acetaminophen and ibuprofen unless advised by your doctor.

What to watch

• drinking and urine output
• breathing
• alertness between fever doses
• new rash, especially one that does not fade with pressure

For symptom-focused advice on a child's temperature, see fever in children.

How doctors assess fever

A clinician will ask about duration, other symptoms, vaccinations, sick contacts and travel, then examine the ears, throat, chest, belly, skin and joints. Depending on age and findings, tests may include a urine test, rapid strep or flu and COVID-19 tests, blood tests, chest X-ray, or a lumbar puncture in young babies or if meningitis is suspected.

Prevention

• keep vaccinations up to date, including flu and COVID-19
• wash hands frequently
• keep children home from daycare or school until 24 hours without fever, without fever-reducing medicine

Frequently asked questions

What temperature is a fever in a child?

A fever is a temperature of 38 °C (100.4 °F) or higher, measured rectally in babies and young children. Oral, ear and forehead readings are reasonable in older children. Armpit readings tend to be lower and less reliable.

When should I worry about my child's fever?

Seek urgent care for any fever in a baby under 3 months, a child who is very sleepy, floppy or hard to wake, has trouble breathing, a rash that does not fade, a stiff neck, signs of dehydration, or a fever of 40 °C (104 °F) or more.

How long can a fever last in a child?

Most viral fevers last 2 to 3 days and up to 5 days. Call your doctor if fever lasts more than 24 hours in a child under 2, more than 3 days in an older child, or 5 days or more at any age.

Should I wake my child to give fever medicine?

No. Sleep helps recovery. Fever medicine is for comfort, so if your child is sleeping comfortably, you do not need to wake them. Do check that a sleeping child is breathing normally and can be woken.

Can teething cause a fever?

Teething can cause a slight rise in temperature, but not a true fever of 38 °C (100.4 °F) or higher. If a teething baby has a fever, look for another cause, such as an infection.