Last time I had a fever, I was lying in bed shivering, my joints ached, and I had a general sense of malaise. My mom came and laid a cool cloth on my forehead and told me she’d get me some aspirin in a bit, but that it was important to let my body do what was natural to fight off the illness. She admonished me to drink plenty of soup to stay hydrated.
After I recovered, I started thinking about fevers. They’re a pack of contradictions: they help our immune system fight off infection but we readily treat them. A few degrees is enough to provide an unsuitable environment for disease, but not so much that we’ve evolved to be at that temperature all the time. The fever is there to help us, but the symptoms are often more debilitating than the disease.
Why do we get fevers?
The downsides of being 101 degrees
Allegedly, fevers help treat an infection. This is how the story goes: your body has been invaded by some kind of foreign contaminant, and fever is your body’s immune reaction. It’s responsible for burning off any impurities in my system and fighting off illness that can’t survive at those higher temperatures.
On the surface, that makes sense. We boil things to make them safe to drink, and we know that bacteria can’t survive at higher temperatures. But the second you start thinking about the tradeoffs your body makes, it starts to fall apart.
Historically, fevers have often been more dangerous than the illness. Dehydration is rampant when your body’s temperature goes above the normal 98.6 degrees Fahrenheit, and you’ll often feel a lack of appetite, weakness, sore joints and headaches and all of which would make you weaker and less able to fight off disease. Go above 104 degrees and you start getting delirium and convulsions.
All in all, our body is optimized to work at around 98.6 degrees. That’s the temperature our bodies revert to, that our hypothalamus will work to bring us back to. Surely if it were optimal to fight off illness, our bodies would have developed to run at a degree or two higher? So many symptoms caused by fever actually make you worse at getting back to healthy homeostasis: not wanting to eat, being dehydrated, too weak and achy to move. Why is it then, that despite the dangers of fevers, that we continue to have them?
What do fevers actually do?
It turns out that common knowledge has it the wrong way around. Fever is not the immune response: it’s the trigger to start an immune response.
As your body heats up past a certain threshold, it sets a series of immune responses in motion, signaling to your body to take appropriate action against infection. A specific signaling pathway called the Nuclear Factor kappa B (NF-κB) starts switching on and off your immune response as needed. But the lower your body temperature, the slower these proteins are to respond.
If you’re running a fever? They’re much faster and more intense.
The findings of this research go beyond just explaining how fevers actually benefit your immune system by acting as the heralds to get everything up and running. The relationship between temperature and the NF-κB signaling pathway has more ramifications, especially when you think about it in conjunction with how our bodies cycle through temperatures throughout the day.
For example, it might help explain why humans are more prone to colds and flu in the colder winter months, or why we’re more likely to get sick when we’re jetlagged and don’t have the normal body temperature fluctuations between waking and sleeping.
Our bodies are complicated and we’re still learning.
Sleep regulates body temperatures, that regulate signaling pathways, which regulate our immune response, which actually produces proteins that feedback into those same signaling pathways, as well as others. It all works to keep us healthy.
Fevers do a lot more for us than fight off infection. They’re part of a very complex system that involves the various parts of our bodies talking to each other to get the best response. It’s a temporary measure to let the right pathways know to kickstart the immune response, so while it may cause discomfort and even be actively harmful in some cases, it’s a vital part of self-regulating our bodies.
We still don’t understand everything about it, but this research has opened up the door for new questions to ask.
It’s strange to think that even in 2019, there’s a lot we don’t understand about our own bodies. And yet we’re plagued with bad medicine that “everyone knows,” incorrect common sense, counterintuitive research that people don’t like to believe, not to mention all the anti-vaxxers. We’re slow to learn. But we are demystifying how the human body works, one pathway at a time.
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