What Is Considered a Fever for Babies, Toddlers, and Children?

A fever is any body temprature which is above the "norm." But is 99 a fever? What about 100.4? Two pediatric experts explain what is considered a fever for children of every age.

Taking a young child's temperature

Maria Manco / Stocksy

Children run fevers, often and frequently. In fact, from teething to fighting infections, there are many different reasons why your child might experience a fever. But when do you let fevers run their course (as a normal part of developing and strengthening their immune system), and when do you need to give them medication or see a provider? And what is considered a fever anyway?

To answer these questions and more, we spoke with Emily Wisniewski, a board-certified pediatrician with Mercy Medical Center in Baltimore, who provides comprehensive care for children from infancy through adolescence. We also spoke with Shelby House, an outpatient nurse with Compass Health Network, to share her experience with pediatric patients.

What Is a Fever?

A fever is a normal response from the body to fight infection. Typically, a healthy body temperature is around 98.6° Fahrenheit; however, there is variation. Medical providers consider anything higher than 100.4° Fahrenheit (38° Celsius) a fever.

What Causes Fevers in Infants and Children?

Most infants and children will experience fevers often during their childhood. Dr. Wisniewski advises these causes can fall into one of two categories.

Common causes

"Fevers can be caused by many different things," says Dr. Wisniewski. "Most commonly, they are going to be infections—for example, from viruses and bacteria." Common childhood illnesses caused by these infections can range from a cold to the flu. House also adds what she most often sees in her work, "Usually the infections we see stem from anywhere in the body, but common infections seen in childhood include infections of the respiratory system, ear infections, or urinary tract infections,".

Rare causes

If your infant is wearing too many layers, or your toddler has too many blankets or coverings in bed, they may overheat, which can raise their body temperature. Teething fevers can also occur, though these are usually low-grade and short-lived. Fevers can also result from more serious, but rare diseases, like cancer or rheumatological disease.

What Are the Signs of Fever in Infants and Children?

The signs of fever in infants and children vary depending on your child's age. These signs can include, but are not limited to:

  • A high body temperature
  • Non-stop, inconsolable crying in newborns and infants
  • Your child is unusually lethargic and isn't acting like themselves (like being excessively sleepy even after a full-nights sleep)
  • Unexplained rash, headaches, body aches, stiffness, or other pain
  • Excessive diarrhea or vomiting, or seizures

"Common signs of fever that trigger most parents to bring their child into a doctor, urgent care center, or hospital include a temperature of 100° Fahrenheit or higher," House says. "Parents will also bring their child in if they're looking flushed, not eating or drinking eating well, and increased fussiness," she adds.

How Do You Know If Your Child Has a Fever?

Your child's temperature reading can differ depending on where the temperature is taken. In addition to an increased body temperature, be on the lookout for other symptoms like flushed skin, a decrease in your child's regular activity level, or an increased/racing heart rate.

Is 99 degrees a fever?

Because body temperature varies from person to person and the temperature reading can be impacted by where it's taken, readings over 99° Fahrenheit can be considered low-grade. That said, it's important to note that most physicians recognize body temperatures higher than 100.4 degrees Fahrenheit as a true fever.

Does the threshold for a fever change depend on how it is measured?

In short, yes. There are several different ways to take your child's temperature, and the thresholds do vary depending on how the temperature is taken. Before deciding how to take their temperature, make sure to follow the guidelines based on their age.

Armpit: If the reading is above 99° Fahrenheit it is considered a fever. This method of taking your child's temperature is recommended for any age, but especially younger children.

Ear: A reading of 100.4° Fahrenheit or higher is considered a fever. Try this method with your child who is six months old or older.

Oral: If the reading is 100° Fahrenheit or higher using this method it is considered a fever and should be used for children four years old and up.

Rectal: This method of taking your child's temperature is the most accurate. A reading of 100.4° Fahrenheit or higher is considered a fever. This is most commonly used for children three years old and younger.

Temporal (forehead): You can run this temperature reading over your child's forehead if they're four years old or older. A temperature of 100.4° Fahrenheit or more is considered a fever.

When to worry: What to know about "high" fevers in babies, infants, and children

When your kids are too little to tell you what's wrong, parents worry anytime their little one seems sick. But when do you really need to worry about high fevers in babies, infants, and children?

"Any baby younger than two months old needs to be seen by a doctor. Fevers in this age group can be a sign of a serious infection, and they should be seen in the emergency department immediately," says Dr. Wisniewski. "The visit may include blood, urine, spinal fluid, viral testing, x-rays, and hospitalization. It's important to not give these babies any medications," she adds.

What Is the Best Treatment for Fevers in Infants and Children?

This ultimately depends on the child's age. As mentioned above, the treatment for infants under two months old should be determined and administered by their medical provider. But for older babies and children, the best route is different.

For babies from two months to six months, Dr. Wisniewski says getting them to the doctor immediately isn't as urgent. "As long as your child is acting like themselves and drinking well, you can give Tylenol (acetaminophen) to make your kiddo more comfortable." However, she also recommends that If the fever doesn't get better in the following two to three days, to touch base with your pediatrician.

For babies older than six months, Dr. Wisniewski says parents can alternate between different medications. "At this age, you have the option of Tylenol (acetaminophen) or Motrin (ibuprofen) —but the same rules apply. If your child isn't getting better in a few days or appears unwell, call your pediatrician." In addition to medication, making sure your child gets plenty of rest and stays hydrated will aid in their recovery.

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