Why do fevers spike at night?

Question

When I’m really sick and have a fever, it always reaches the highest temperature during the evening. I’ve heard people suggest covering up a sick child when they go to bed to break the fever as their temperature spikes at night. So, why do fevers reach the highest temperatures during this part of the day?

Answer 1

When you’re sick, a certain region of your brain sends signals to the rest of your body to increase the natural temperature. Mostly, that’s why fevers spike at night.

The hypothalamus resets your body’s temperature to one that is higher than normal when you have a fever for unclear reasons, but one guess is that the heat helps your body’s immune system fight against bacteria. Bacteria has a temperature range that it can survive in safely just like we do as humans. However, higher temperatures tend to be more deadly to bacteria than colder ones, and it is much easier for the human body to deal with a higher temperature in order to fight off these unwanted invaders that are sensitive to heat.

Answer 2

Why do fevers spike at night?

Body temperatures naturally rise at night whether you’re healthy or sick, so this natural temperature spike equally affects fever spikes at night. There are three main reasons why temperature rise happens naturally regardless of variables like illness:

• The small gland at the base of your brain, called the hypothalamus, sends cues for adjusting temperature.
• Vital functions of human body, like heartbeat, muscle activity.
• The temperature of your environment.

These factors all contribute to why the body heat rises at night, and this routine temperature rise only makes an already high fever rise even more. And if you sleep with a lot of blankets, without a fan, or even with an animal snuggled up next to you these will contribute to a rise in body heat as well.