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The American Academy of Pediatrics defines a fever in a child as a rectal temperature of 100.4 degrees Fahrenheit or greater.
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In most cases, a fever isn’t anything to worry about. Instead, it’s a sign the immune system is working as it should to fight infection.
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One of the times parents should worry about a fever is when it develops in a baby who is younger than 3 months old.
When to worry about your child’s fever
As a mom and a pediatrician, Elizabeth Meade, M.D., understands why many parents get concerned when their baby or child spikes a fever.
“It’s one of the most common questions I get from parents, and I know it can be anxiety-provoking,” says Dr. Meade, who serves as the medical director of quality for pediatrics at Providence Swedish Pediatric Hospital Medicine in Seattle.
Yet she wants to reassure parents that, most of the time, fevers — even high fevers — are nothing to worry about.
Typically, Dr. Meade says, “it’s something that’s part of our bodies’ natural response to infection, and it’s actually a good thing.”
What is a fever?
Normal body temperature is around 98.6 degrees Fahrenheit. The American Academy of Pediatrics (AAP) defines a fever in a child as a rectal temperature of 100.4 degrees Fahrenheit or greater. If you take your child’s temperature orally (by mouth), a fever is considered a reading of 99 degrees Fahrenheit or higher.
Most fevers are caused by infections from viruses, such as a cold or the flu, or from bacteria, such as strep throat. What’s important to know is that the fever itself is not the infection. It’s merely a sign the body is working to fight the infection.
Common myths about fevers
In addition to the belief that fevers are bad, there are other common myths worth dispelling.
Some of these myths include:
- Myth #1: The higher the temperature, the more serious the illness.
The reality: Although this can be the case in teens and adults, it’s not always true in children ages 12 and under. That’s because a child’s immune system isn’t fully developed yet. - Myth #2: High fevers cause seizures.
The reality: Febrile seizures aren’t actually caused by high fevers. Instead, they’re caused by a sudden spike in temperature. - Myth #3: You have to take your child’s temperature rectally for it to be accurate.
The reality: While most rectal temperatures are accurate, they aren’t always necessary.
How to take your child’s temperature
You can take your child’s temperature several ways, including with a:
- Digital thermometer, which can be used to take your child’s temperature in their mouth or their rectum
- Ear thermometer, which can emit a beam into your child’s eardrum to determine their body temperature
Just make sure you clean the thermometer both before and after using it, with lukewarm soapy water or rubbing alcohol and a cool water rinse.
The AAP recommends taking your child’s temperature rectally until they’re 4 or 5 years old.
3 things to keep in mind about fevers
There are a few things to remember about fevers:
- Body temperature fluctuates throughout the day. You can typically count on temperatures to be lowest at night and in the early morning, and highest in the late afternoon and early evening.
- Infants tend to have higher temperatures than older children.
- Don’t confuse a fever with heatstroke, which isn’t caused by infection but by being in an environment that’s too warm for too long. Heatstroke can cause the body temperature to reach dangerous levels, and can even lead to death.
When to worry about a child’s fever
Although fevers aren’t something to worry about most of the time, there is one exception: When your baby is younger than 3 months old and spikes a temperature that’s higher than 100.4 degrees Fahrenheit. In that case, Dr. Meade says, you should get them in to see their pediatrician right away. If your child’s doctor’s office is already closed for the day, take them to the emergency room.
The concern with fevers in newborns is they haven’t had their first set of vaccines yet, so their bodies aren’t equipped to fight off dangerous bacterial infections, like diphtheria, which affects the upper respiratory tract, and pertussis, which also affects the respiratory tract and is commonly known as whooping cough.
In addition to a fever in a baby younger than 3 months old, the AAP recommends calling the pediatrician right away if your baby or child:
- Has a fever that repeatedly rises higher than 104 degrees Fahrenheit
- Looks very sick, is unusually drowsy or is extremely fussy
- Has other symptoms, such as:
- A stiff neck
- An unexplained rash
- Repeated vomiting or diarrhea
- Severe ear pain
- Severe headache
- Severe sore throat
- Has immune problems, such as sickle cell disease or cancer, or is taking steroids
- Has had a seizure
If your child has a fever, is older than 3 months old and is otherwise healthy, Dr. Meade says, their pediatrician will likely tell you to keep them comfortable by giving them fever-reducing medicines, such as Tylenol® or Advil®, and plenty of fluids at home. If they have a fever, are older than 3 months old and don’t appear to be bothered by the high temperature, don’t feel obligated to give them medicine.
“We really reserve those for times when kids aren’t feeling well, and those medicines can help them feel better,” Dr. Meade says.
Still, call your child’s doctor if you’re ever concerned about a fever.
“It’s always better to check in and be safe than sorry,” Dr. Meade says.
Contributing caregiver
Elizabeth Meade, M.D., is a pediatrician and medical director of quality for pediatrics at Providence Swedish Pediatric Hospital Medicine in Seattle.
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Related resources
Kids’ respiratory illnesses 101
Finding the right pediatrician for your growing family
Sick kid? How to get through the flu.
This information is not intended as a substitute for professional medical care. Always follow your health care professional’s instructions.
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