Understanding fever in kids

August 5, 2015 Kathleen Goetz, MD

portrait close up of a young girl with a thermometer in her mouth


In this article:

  • A Swedish pediatric emergency physician explains myths and facts about fevers in children.

  • Fevers are a sign of the body’s immune system fighting an illness, which means they can be helpful.

  • Even high fevers or fevers that come back are not always a cause for concern.

As a pediatric emergency physician in practice for 18 years, I have seen a great many children with fevers. I also see a great many parents and other caregivers who are very concerned about fevers but are reassured when factual information.

Fever is a marker of illness and is very concerning in specific circumstances. Fever over 100.4 in any infant less than 60 days of age is reason to seek urgent medical evaluation. However, once children get beyond the newborn period, fever is much less concerning to medical professionals. The following information can help you better understand fever, and help you care for your child without unnecessary worrying. Fever myths lead to fever phobia while in fact, fevers are harmless and often helpful.

MYTH: My child feels warm, so she has a fever.

FACT: Children can feel warm for many reasons. Examples are playing hard, crying, getting out of a warm bed or hot weather. They are "giving off heat." Their skin temperature should return to normal in 10 to 20 minutes. However, about 80% of children who act sick and feel warm do have a fever. If you want to be sure, take the temperature. These are the cutoffs for fever using different types of thermometers:

• Rectal, ear or forehead temperature: 100.4° F (38.0° C) or higher
• Oral (mouth) temperature: 100° F (37.8° C) or higher
• Under the arm (armpit) temperature: 99° F (37.2° C) or higher

MYTH: Oral temperatures between 98.7° and 100° F (37.1° to 37.8° C) are low-grade fevers.

FACT: These temperatures are normal. The body's normal temperature changes throughout the day, peaking in the late afternoon and evening. A true low-grade fever is 100° F to 102° F (37.8° - 39° C).

MYTH: All fevers are bad for children.

FACT: Fevers turn on the body's immune system. They help the body fight infection. Normal fevers between 100° and 104° F (37.8° to 40° C) are good for sick children.

MYTH: Fevers above 104° F (40° C) are dangerous. They can cause brain damage.

FACT: Only temperatures above 108° F (42° C) can cause brain damage. It's very rare for the body temperature to climb this high, and it only happens if the person is in an environment where the air temperature is very high — for example, when a child is left in a closed car during hot weather.

MYTH: All fevers need to be treated with fever medicine.

FACT: Fevers only need to be treated if they cause discomfort. Usually, fevers don't cause any discomfort until they go above 102° or 103° F (39° or 39.5° C).

MYTH: With treatment, fevers should come down to normal.

FACT: With treatment, fevers usually come down 2° or 3° F (1° or 1.5° C).

MYTH: If the fever doesn't come down (if you can't "break the fever"), the cause is serious.

FACT: Fevers that don't respond to fever medicine can be caused by viruses or bacteria. It doesn't relate to the seriousness of the infection.

MYTH: Once the fever comes down with medicine, it should stay down.

FACT: With most viral infections, a fever will normally last for two or three days. Therefore, when the fever medicine wears off, the fever will return. The fever will go away for good once your child’s body overpowers the virus (usually by the fourth day).

MYTH: If the fever is high, the cause is serious.

FACT: If the fever is high, the cause may or may not be serious. If your child looks very sick, the cause is more likely to be serious.

MYTH: The exact number of the temperature is very important.

FACT: How your child looks is what's important. The exact temperature number is not.

Remember: that fever is fighting off your child's infection. Fever is one of the good guys. 

Find a doctor

If you have questions about your child’s fever, contact the Pediatrics department at Swedish. We can accommodate both in-person and virtual visits.

Whether you require an in-person visit or want to consult a doctor virtually, you have options. Swedish Virtual Care connects you face-to-face with a nurse practitioner who can review your symptoms, provide instruction and follow up as needed. If you need to find a doctor, you can use our provider directory.

Join our Patient and Family Advisory Council.

This information is not intended as a substitute for professional medical care. Always follow your health care professional's instructions.

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