How A Fever Works

Have you ever wondered the following:

  • How does a fever work?
  • Why does my body become so cold?
  • How exactly does the fever help me?

I certainly have.

I took the time to read on it several years ago, but for the sake of this post I read it all again.

I’ll try to summarize it in simple terms—without too much jargon:

What Is A Fever?

A fever is an increase of body temperature to an abnormal level usually caused by pyrogens. Pyrogens are substances that produce a rise in body temperature. The hypothalamus—a structure of the brain—is the area in charge of controlling body temperature. The control of body temperature is named thermoregulation. For this reason, the hypothalamus is sometimes called the Body’s Thermostat.

How Do Pyrogens Affect The Hypothalamus?

Pyrogens affect the thermoregulation control center. When this happens, the reference value for the body’s normal temperature is temporarily increased. This leads to your body feeling that it is colder than it should be. This sensation leads the body to attempt to heat itself up—and to achieve this, symptoms can occur, i.e., shivering.

Ok, I Am Cold Now. I Take My Blanket. I Am Still Cold. Is It All Worth It?

If the fever is slight, here are two reasons why it is beneficial—I am sure there are other reasons as well:

  • It increases the speed of the body’s defensive reactions to aid in killing pyrogens faster. 
  • It—by means of the liver and spleen—lowers the amount of iron and zinc. Bacteria needs iron and zinc to multiply. This lowering of zinc and iron is done to hinder bacteria proliferation.

Therefore, instances of fever that do not rise the body temperature too much are considered to aid in defense against external agents. However, when the body’s temperature increases drastically, certain enzymes—substance in your body that are essential to producing chemical reactions—deactivate and this can be dangerous.

Here is a passage taken from a Science Daily article from 2011:

“Having a fever might be uncomfortable,” said John Wherry, Ph.D., Deputy Editor of the Journal of Leukocyte Biology, “but this research report and several others are showing that having a fever is part of an effective immune response. We had previously thought that the microbes that infect us simply can’t replicate as well when we have fevers, but this new work also suggests that the immune system might be temporarily enhanced functionally when our temperatures rise with fever. Although very high body temperatures are dangerous and should be controlled, this study shows that we may need to reconsider how and when we treat most mild fevers.”

That just about sums it up without going through the details of everything occurring in the body when you are swarmed by some unwanted pyrogen visitors.


How much of this did you already know? And do you know of other key reasons as to why fevers occur?

References: Atlas de poche de physiologie (1992); Vulgaris Médical; Science Daily.

One thought on “How A Fever Works

  1. Pingback: What Do You Do When You Feel Sick? | Jonathan Naylor

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s