Why does the body effectively kill itself trying to protect itself from some allergens? (Peanuts, latex, etc)
In: Biology
An allergy is when your body finds a not-dangerous substance and think it’s dangerous.
In general, bodies and evolution aren’t smart at long term actions. If you’re going to die in two seconds from the dreaded peanut poison, your body is more than happy to overreact, such that you die in a much more generous two hours.
The human immune system evolves in response to existing threats, not in anticipation of specific ones. It has a few basic defensive moves that it uses when it thinks something bad has entered your body, like releasing antibodies. With some unfamiliar things that trigger it, it basically doesn’t know what to do and overreacts by sending out too many of them.
There is some evidence that most allergies are formed when your immune system encounters a material it didn’t encounter in early childhood.
Born into a primitive group that eats lots of shellfish? You probably touched tasted ate shellfish at a very young age. So probably no allergy later in life.
Our ancestors didn’t tend to move great distances during one life, so the shellfish eater probably never meets the peanut eater.
So it’s advantageous that the immune system overreacts to the new. It was very unlikely this new stuff is actually food. It’s probably some kind of contamination present in small amounts. I mean, who chooses to just shove a handful of seeds in their mouth when it’s not something they’ve eaten before, and their mother ate, etc.
So it’s not likely a primitive person would encounter an allergen. And if they did, it’s not likely they’d be stupid enough to put even a little in their mouth. And if they did, boy they now know not to eat a mouthful of whatever that was.
Finally, it’s an evolutionary advantage if it kills 1 in 1000 by allergy but prevents the death of 2 in 1000 by ifection/poisoning.
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