Fever is the body's normal and healthy reaction to infection and other illnesses, both minor and serious. Fevers help the body fight infection. Fever is a symptom, not a disease. In most cases, fever means your child has a minor illness. Often you must look at your child's other symptoms to determine how serious the illness is. Although it may be scary when your child's temperature goes up, fever is not harmful.
The average normal body temperature is about 98.6°F (37°C). It usually rises during the day from a low of 97.4°F (36.3°C) in the morning to a high of 99.6°F (37.6°C) in the late afternoon. Each child has a normal temperature range that may be different from another child's. Mild increases to 100.4°F (38°C) can be caused by exercising, wearing too many clothes, taking a hot bath, or being outside in hot weather.
Temperature varies depending on how you take it. The most common ways to measure it are:
You can also use:
- Forehead thermometers.
Some methods may not be as reliable or accurate as others. For information about taking accurate temperatures, see the topic Body Temperature.
If you think your child has a fever but you are not able to measure his or her temperature, it is important to look for other symptoms of illness.
Children tend to run higher fevers than adults. The degree of fever may not indicate how serious your child's illness is. With a minor illness, such as a cold, a child may have a temperature of 104°F (40°C), while a very serious infection may not cause a fever or may cause only a mild fever. With many illnesses, a fever temperature can go up and down very quickly and often, so be sure to look for other symptoms along with the fever.
Babies with a fever often have an infection caused by a virus, such as a cold or the flu. Infections caused by bacteria, such as a urinary infection or bacterial pneumonia, also can cause a fever. Babies younger than 3 months should be seen by a doctor anytime they have a fever because they can get extremely sick quickly.