This is a follow up to the post I wrote on whether a fever actually helps you while you are sick (the original blog post is here).
We know a fever occurs when the body reacts to an infection. Your body temperature can go up to 38 degrees Celsius as a mild fever, to 40 degrees as a high fever. And the higher your body temperature is, the more of that ‘chill’ you feel. You know, that really uncomfortable sensation of being cold no matter how many blankets you’ve piled on.
If we’re so hot, why do we feel so cold?
This is because of how your brain controls your body temperature. I’ll try and explain this as simply as I can. Please enjoy my crude drawings.
First, a part of your brain (the hypothalamus) sets a normal temperature for everyday functioning. It monitors your body for this temperature and makes changes automatically to keep it that way (like a thermostat). In Summer when it’s really hot out, it makes you sweat to cool down. In Winter, your blood vessels shrink and your muscles make you shiver to create heat to warm up (or until you put on some warm clothes).
When you get sick, your immune system sends signals to your brain to increase your body temperature.
Your brain then says ‘ok, let’s set the temperature monitor a couple degrees higher’. Your brain then sees this new temperature as the ‘normal’ temperature. But because your body is actually colder than the thermostat, the brain thinks you need to warm up.
Remember what I said earlier about how you react in Summer and Winter? When it’s hot, you sweat. When it’s too cold, your blood vessels shrink to redirect warmth to your organs and your muscles cause you to shiver to create heat. The same thing happens when you have a fever because your brain thinks you are cold. It sends out hormones to cause these reactions.
And that’s really about it, that’s why you feel cold with a fever.
You feel perpetually cold because your immune system is always asking your brain for heat, which constantly sends signal to your body to create aforementioned heat. Thing is, it’s not very energy efficient to make heat this way, not to mention it makes you pretty tired if the fever doesn’t go away. Your body is working hard fighting bad guys and trying to boil them to death.
Eventually when your immune system wins the fight against the infection, it slows down on the demand to be hot. The hypothalamus in your brain goes back to status quo and returns you to your actual, normal temperature.
Let me finish this by saying there’s a lot of summarising here. There’s a lot of detail left out that are biologically and medically important/significant. But my purpose here is to make sure the average person can understand this, simply because they are curious.
Originally published at http://haveyoueverwondered123.wordpress.com on July 16, 2022.
