Surprising Facts About Fevers
All measurements are not the same.
A child has a fever when the temperature is at or above one of these levels, according to the U.S. National Library of Medicine:
- 100.4°F (38°C) measured in the bottom (rectally)
- 99.5°F (37.5°C) measured in the mouth (orally)
- 99°F (37.2°C) measured under the arm (axillary)
Most adults are considered to have fevers when they have a temperature above 99 to 99.5 degrees, (37.2 - 37.5°C), depending on the time of day. Taking a temperature rectally is the most accurate method in children under 3 years of age because it best measures the body’s core readings, but it’s not the only way to get a reading. You can also try going under the armpit or in the mouth (for children over age 2), says Dr. Michael McKenna, a pediatrician with Riley at IU Health. Ear thermometers can also be used, although they have a tendency to be inaccurate for higher temperatures, he adds.
There’s a reason your body forms a fever.
It’s how you best fight off infection. Most of the bacteria and viruses that can make us sick do best at a temperature of 98.6°F. Go above that, and your immune system can start to destroy the bugs before they do damage.
Not all fevers are due to illness.
Children may have a low-grade fever (under 101.5 for children over two months, or 100.4 for infants under two months) for one or two days after getting some common immunizations. Teething can also cause a slight increase in a child's temperature, although not higher than 100°F. Fevers can also come from a reaction to an allergy to food or medication, or from becoming overheated at play or in the sun.
High fevers aren’t always a cause to panic.
Children can get a fever of up to 104 even with a simple cold or other viral infection. When you should call your health care provider: If your baby is younger than three months, always get in touch. Otherwise, call right away if a fever is accompanied by a seizure, lethargy, irregular breathing, stiff neck, confusion, or other signs of a serious illness.
Body temperature naturally changes over the course of the day.
Normal body temperature ranges from 97.5°F to 98.9°F (36.4°C to 37.2°C). It tends to be lower in the morning and higher in the evening. Most health care providers consider a fever to be 100.4°F (38°C) or higher. High fevers or certain viruses may bring on seizures or confusion in children.
Three Ways to Fight a Fever
- Keep room temperatures comfortable (65 to 70 degrees F), not too hot or cool.
- Try giving a lukewarm bath or sponge bath, especially after taking medication. Don’t give ice baths or alcohol rubs—they can cool the skin but often can make your child shiver, which raises core temperature.
- Children especially should stay hydrated and drink plenty of clear fluids, such as water, popsicles, soup, and gelatin. Avoiding giving fruit juice, apple juice and sports drinks in large quantities, since they can upset the stomach or throw off the balance of electrolytes in younger children.