Signs of a fever and when to worry

A fever is a higher-than-normal body temperature. It’s usually a sign that the body is waging a war against infection. Here’s how to tell when you need to be concerned about a fever:

If your baby is under 3 months old and has a temperature of 100.4 degrees F or higher, call the doctor immediately. A baby this young needs to be checked for serious infection or disease.

For a baby 3 months old or older, the most important thing is how he looks and acts. If he appears well, is taking fluids, and has no other symptoms, there's no need to call the doctor unless the fever persists for more than 24 hours or is 104 degrees F or higher.

If your baby is between 3 months and 6 months and has a fever of 101 degrees F or higher, or is older than 6 months and has a temperature of 103 degrees F or higher – call the doctor if he also has symptoms such as:

  • Loss of appetite
  • Cough
  • Signs of an earache, such as pulling on his ear
  • Unusual fussiness or sleepiness
  • Vomiting or diarrhea
  • Noticeably pale or flushed
  • Fewer wet diapers or peeing less
  • Unexplained rash (small, purple-red spots that don't turn white or paler when you press on them, or large purple blotches, can signal a very serious bacterial infection)
  • Breathing difficulty (or breathing faster than usual) even after you clear his nose with a bulb syringe. This could indicate pneumonia or RSV.

If your baby has a temperature that’s lower than 97 degrees F, this also warrants a call to the doctor.

Fever can be a symptom of COVID-19. If you believe your child has been exposed to COVID-19, call your child's doctor.

Here's how to take your child’s temperature.

Note that different kinds of thermometers are more accurate than others. Most doctors still ask you to use a rectal thermometer and the temperatures above are based on rectal readings (although studies show that a temporal thermometer is just as accurate.)

But some will recommend that you take your baby's temperature under the armpit (axillary) first and if that temperature is above 99 degrees F, then do a rectal reading.

Note that your child’s temperature can change depending on the time of day (it’s often higher in the afternoon) or on how active your child’s been (crawling, cruising, and running kids are hotter).

What to do if your baby or child has a fever

Since fever is part of the body's defense against bacteria and viruses, some experts suggest that an elevated temperature may help the body fight infections more effectively. (Bacteria and viruses prefer an environment that's around 98.6 degrees F.) A fever also tells the body to make more white blood cells and antibodies to fight the infection.

On the other hand, if your baby or child's temperature is too high, he'll be too uncomfortable to eat, drink, or sleep, making it harder for him to get better.

Here are some basic steps you can take to make your child comfortable:

Remove layers of clothing so your child can lose heat more easily through her skin. Dress her in one light layer. If she's shivering, give her a light blanket until she's warm again.

Place a cool, damp washcloth on your child's forehead while she rests.

Offer plenty of fluids. Older babies and children can have chilled foods, such as ice pops and yogurt, to help cool the body from the inside out and keep them hydrated.

Give your child a lukewarm tub bath or a sponge bath. As the water evaporates from her skin, it will cool her and bring her temperature down. Don't use cold water. It can make her shiver and cause her body temperature to rise. Likewise, don't use rubbing alcohol (an old-fashioned fever remedy). It can cause a temperature spike and possibly even alcohol poisoning.

Use a fan. Again, you don't want your child to be chilled. Keep the fan at a low setting and aim it nearby her to circulate the air around her rather than blow directly on her.

Stay indoors in a cool place. Or, if you're outside, stay in the shade.

Medicine for fever is an option if the fever is making your child uncomfortable and your doctor says it's okay. Acetaminophen or ibuprofen will help bring down the fever. (Ibuprofen isn't recommended for babies under 6 months or for children who are dehydrated or have persistent vomiting.) When giving medicine:

  • Be careful with the dose. Your child’s weight will determine the right dose. Always use the measuring device that comes with the medicine to give your child exactly the right amount.
  • Don't give fever-reducing medicine more often than is recommended. The directions will probably say that you can give acetaminophen every four hours (up to a maximum of five times per day) and ibuprofen every six hours (up to a maximum of four times per day).
  • Never give your child aspirin. Aspirin can make a child more susceptible to Reye's syndrome, a rare but potentially fatal disorder.
  • Don’t give your child over-the-counter cough and cold preparations. Most doctors don't recommend these products for babies and young children. And they may already contain ibuprofen or acetaminophen, so you risk giving your child too much medicine.

Febrile seizures and other complications

Fever is usually a normal part of the body’s healing process. But there are complications to be aware of:

Febrile seizures

Fevers sometimes cause febrile seizures in babies and young children. They're most common in children between the ages of 6 months and 5 years.

In most cases, the seizures are harmless, but that doesn't make it any less terrifying if your child's having one. He may roll his eyes, drool, or vomit. His limbs may become stiff and his body may twitch or jerk.

Read more about febrile seizures and how to handle them.

Fever that keeps coming back

Fever-reducing medicine brings down body temperature temporarily, but it doesn't affect the bug that's causing the infection. So your child may run a fever until his body is clear of the infection. This can take at least two or three days. Your doctor may want to see your child if his fever lasts longer than three days.

Some infections, such as influenza (the flu), can last five to seven days. And if your child is being treated with antibiotics to fight a bacterial infection, it may take 48 hours for his temperature to fall.

Fever with no other symptoms

When a child has a fever that isn't accompanied by a runny nose, a cough, vomiting, or diarrhea, figuring out what's wrong can be difficult.

There are many viral infections that can cause a fever without any other symptoms. Some, such as roseola, cause three days of very high fever followed by a light pink rash on the trunk.

More serious infections, such as meningitisurinary tract infections, or bacteremia (bacteria in the bloodstream), may also trigger a high fever without any other specific symptoms. If your child has a fever of 102.2 degrees F or higher for longer than 24 hours, call the doctor, whether or not he has other symptoms.

Brain damage

It's possible, but it's extremely unlikely.

It's not unusual for a sick child to run a temperature of 104 or even 105 degrees F. To cause brain damage, a child's temperature would need to reach 107.6 degrees F – hard to imagine, unless the child was trapped in a hot car, for instance, or was very overdressed while feverish.

Again, fever is common, normal, and a sign your baby’s body is doing what it’s designed to do when faced with an infection. But you’re the best judge of when something is wrong. If you’re concerned about what’s happening with your child’s temperature, call your doctor.