Ask Dr. Universe – Fever

Dr. Universe: Why do we get a fever when we are sick? – Marcelina, 11, Ovid, N.Y.

Dear Marcelina,

Lots of warm-blooded animals get sick, including cats. I’ve had a fever before, but I wasn’t entirely sure why we warm up when we get sick. I decided to ask my friend and professor Phil Mixter at Washington State University.

Mixter is curious about the germs, or microbes, that we all carry around with us. In fact, scientists estimate that humans carry more than 100 trillion of these tiny microbes with them wherever they go. Not all of these microbes are bad, but some of them can make you sick.

Thankfully, a lot of animals—from starfish to cats to humans—also have an immune system that helps them fight off bad germs. In humans, fevers are one way your body helps fight back.

It’s sort of like that story about Goldilocks and the three bears, Mixter said. In the middle of your brain is a control center, the hypothalamus, which helps your body know if it’s too hot, too cold, or just right.

Maybe the last time you went in for a check-up the doctor took your temperature and told you it was somewhere around 98.6 degrees Fahrenheit—or 37 degrees Centigrade for readers outside the United States. That’s a pretty normal temperature for humans.

Cats run a little warmer, with temperatures around 100 degrees Fahrenheit. As we go about our day, sometimes our body temperatures will rise or fall just a little. But if germs come on the scene, things can really heat up.

When your immune system realizes something unusual is going on, some of your white blood cells will release a substance into your blood stream. The substance is made up chemicals that your brain can detect. When the hypothalamus receives the chemical message, it sends an alert back out to the body: Turn up the heat! We’ve got to slow down these germs.

Many microbes that make us sick do best in an environment that is about 98.6 degrees F. The temperature is just right. When we get a fever, the heat helps slow down these troublemakers. You might feel sweaty and hot on the outside, but the microbes are also getting too hot. The heat helps keep them from multiplying rapidly.

One thing a fever can’t really tell us is what kinds of germs are in our system. Sometimes there might be something else going on and we might need to visit with a doctor.

A fever may not make us feel great, but it’s usually a good sign that our body’s immune system has kicked into gear and that we’ll get better real soon.

Dr. Universe