Why Your Body Raises Its Temperature
A fever happens when immune signals tell the brain to raise the body’s temperature setting, creating conditions that can support immune defenses and make it harder for some germs to thrive.
Featured in the Thursday, September 24 edition →
It's often said that a fever is the illness itself — in fact, it is usually a symptom of the body responding to an infection or another trigger.
The hypothalamus, a small control center in the brain, coordinates this body-wide response with the immune system. Fever is one part of a larger defense network that also includes inflammation, mucus, coughing, and tiredness.
Imagine your body has a thermostat that normally keeps the room comfortable. When trouble starts, the thermostat turns up, so the whole room gets warmer while helpers deal with the problem.
Understanding fever helps whenever someone is sick and people are deciding whether to rest, use a fever-reducing medicine, or seek medical care. It also makes clear why lowering a temperature can improve comfort without removing the illness causing it.
Say immune cells detect a virus and release chemical signals. The brain responds by raising the body’s temperature setting, so the person may first feel cold and shiver while their temperature climbs. Once the setting returns to normal, sweating can help release the extra heat.
Chills happen during the climb
Because the new temperature setting is higher than the body’s current temperature, muscles may shiver and blood vessels may narrow to produce and conserve heat.
Fever has built-in limits
The brain can lower the temperature setting again when the immune signals fade, which is why sweating often follows the fever’s peak.
The trigger is not always infection
Immune reactions, some medicines, and other health conditions can all produce fever because they can affect the body’s temperature-control system.