A fever is a temporary increase in your body temperature, often due to an illness. Having a fever is a sign that something out of the ordinary is going on in your body.

For an adult, a fever may be uncomfortable, but usually isn’t a cause for concern unless it reaches 103 F (39.4 C) or higher. For infants and toddlers, a slightly elevated temperature may indicate a serious infection.

Fevers generally go away within a few days. A number of over-the-counter medications lower a fever, but sometimes it’s better left untreated. Fever seems to play a key role in helping your body fight off a number of infections.