Fever Chill

Fever Chill Photo Credit: Clipart.com

It's cold and flu season, which means you might have recently experienced a case of the chills. In this Science Update, you'll find out why that happens.


Getting chills when you're ill. I'm Bob Hirshon and this is Science Update.

Flu activity is starting to pick up around the country. That prompted a listener in Walnut Creek, California to ask why fevers give you the chills.

We consulted Dr. Matthew Kluger of the Medical College of Georgia. He says when you have an infection, it resets your internal thermostat above the normal 98.6 degrees Fahrenheit.


The set point rises to maybe 101, or 102, or 103. And then you feel cold. And you shiver and raise your body temperature to that elevated level.

When the fever breaks, the thermostat gets set back to 98.6. That's when you start to sweat, throw off the covers, and hopefully begin to feel better.

Call us at 1-800-WHY-ISIT with your science question. If we use it, you'll get a free Science Update mug. I'm Bob Hirshon for AAAS, the Science Society.

Making Sense of the Research

With so many medicines and treatments available for all of our pains, illnesses, and discomforts, it's easy to forget that our own bodies have remarkable built-in defenses against disease.

Fever appears to be one of those defenses, although its purpose still isn't fully understood. One benefit of raising your body temperature is that it seems to boost the activity of your immune system. Raising your temperature by a few degrees may also kill some bacteria or viruses that are sensitive to slight temperature changes.

When your body raises its temperature set point, it's really prompting you to do things that raise your body temperature, like wear warm clothes, climb under the blankets, or drink hot liquids. In other words, it's raising your temperature (at least partly) in a roundabout way. By making 98.6 (inside you) feel chilly instead of comfortable, it's pushing you to behave in ways that raise your temperature up a little higher.

Of course, the problem with fever is that it doesn't take much to overheat the human body. That's why many doctors still recommend lowering fever. Drugs like aspirin, acetaminophen, and ibuprofen do this by blocking the production of fever-inducing chemicals called prostaglandins in the brain. They won't help you beat the bug that's making you sick, but they will prevent you from running a dangerously high temperature.

Now try and answer these questions:

  1. Why do you get chills when you get a fever?
  2. How do the chills work indirectly to raise your body temperature?
  3. What would happen if your body's set point lowered to 96 degrees Fahrenheit? How would that affect your behavior?
  4. Lizards, which do not internally regulate their body temperature, have been known to crawl under a heat lamp when they get infections. Why do you think that is?

For Educators

Dr. Kluger's 1986 article "Fever: A Hot Topic", which discusses thermal regulation and set points in more detail, is available from Physiology Online.

The Mayo Clinic offers a comprehensive overview of Fever, from symptoms to prevention and treatment.

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