Fever 101: Everything You Need to Know

It’s easy to lose your cool when your child has an abnormally high temperature. Most fevers are harmless, though, and parents can take comfort in knowing that some are even helpful—they’re a signal that your child’s immune system is working to fight infection by turning up the heat.

And many doctors agree that kids, from toddlers to teens, don’t even need to be given fever-reducing medicines unless they’re uncomfortable or in pain.

A fever is defined as: A temperature higher than 100.4°F (38°C).

What fevers mean by age

  • Infants younger than 3 months of age whose temperature reaches 100.4°F (38°C) or higher should be evaluated by a doctor, because fevers in infants can indicate a serious illness.
  • In kids between 3 months and 3 years of age, a fever of 102.2°F (39°C) or higher requires a call to your pediatrician.

Doctors also recommend taking into consideration how your child looks and feels. Does he look or act sick?

“If your child has a fever but is still interested in playing, and is alert and smiling at you, his fever can probably  be observed with at home treatment. Remember, a fever helps fight off infection, so you don’t necessarily have to give fever-reducing medicine right away,” said Tracy Nailor, MD, MPH, a Pediatric Urgent Care Physician at Children’s Healthcare of Atlanta. “Don’t worry too much if he’s not eating the same amount as when he is healthy. However, if he is weak, having trouble drinking or keeping down fluids, you should call your pediatrician.”

Is it a fever?

If you think your child has a fever, take his temperature. You might assume your child has a fever if you touch his head and he feels warm, but this is not the best way to measure a temperature at home. The most reliable way is to use a digital thermometer. There are several types on the market:

  • Oral (under the tongue or armpit)
  • Tympanic (in the ear)
  • Rectal
  • Temporal artery (on the forehead)

Taking a temperature rectally is the best way to get an accurate measurement, especially in infants. Temperatures taken orally tend to run about a half or full degree lower than others. Whatever method you choose, read the instructions for your thermometer, and when reporting the temperature, be sure to share how you took it.

A high fever may not be a good indicator of how sick your child is. A simple cold or viral infection can cause a fever of 102°F to 104°F (38.9°C to 40°C), but isn’t usually a cause for worry. For infants, serious infections may cause no fever or even an abnormally low body temperature (below 97°F or 36.1°C).

Call your pediatrician right away if your child has a fever with:

  • Rash
  • Sore throat or earache
  • Lasting diarrhea or repeated vomiting
  • Signs of dehydration (urinating less than usual or no tears when crying)
  • Refuses fluids

Call 911 if your child has a fever and with:

  • Severe headache
  • Stiff neck or complains of light hurting his eyes
  • Rash or purple spots that look like bruises on the skin
  • Problems breathing
  • Belly pain
  • Sluggishness or trouble waking up

What is a febrile seizure?

A febrile seizure can occur when your child’s temperature spikes quickly. Symptoms may include loss of consciousness, twitching limbs or convulsions, and confusion or tiredness after the seizure.

“There is no temperature that automatically means your child will have a febrile seizure,” Dr. Nailor said. “How quickly your child’s temperature increases is more important than the actual height of the fever. Children most likely to have a seizure with fever are between 6 months and 6 years of age. This is most often due to viral illness.”

If your child has a febrile seizure, call your pediatrician.

How to treat or reduce a fever at home

If a fever is making your child fussy or uncomfortable, you can give him acetaminophen or ibuprofen. Follow the instructions on the label and measure carefully based on your child’s weight, not age. If your little one is younger than 2 years old, call your pediatrician before giving him any medication.

Avoid giving your child aspirin for his fever, as this can cause Reye’s syndrome, a dangerous and rare disorder that causes brain and liver damage. Additional ways to treat your child’s fever at home:

  • Dress him in lightweight clothing.
  • Give him a bath in lukewarm water. Do not add rubbing alcohol to the water or apply it directly to your child’s skin. Rubbing alcohol is absorbed by the skin and can cause alcohol poisoning.
  • Make sure his bedroom is a comfortable temperature—not too hot or cold.
  • Offer plenty of fluids, ice pops and flavored gelatins to replenish fluids lost to fever.
  • Make sure he gets plenty of rest.

Most doctors say your child can return to childcare or school when his temperature has been normal for 24 hours. If a fever lasts longer than 24 hours in kids younger than 2, or longer than 72 hours in kids older than 2, call your child’s pediatrician.

This content is general information and is not specific medical advice. Always consult with a doctor or healthcare provider if you have any questions or concerns about the health of a child. In case of an urgent concern or emergency, call 911 or go to the nearest emergency department right away. Some physicians and affiliated healthcare professionals on Children’s Healthcare of Atlanta team are independent providers and are not our employees.