Humans have allways lived in within reach of nature and forests, some more than others depending on where you live in the world. But how can we still not be immune to something like pollen by now? Something that we have been affected by every summer ever? Why doesnt our immunesystem adapt to it? Can animals have pollenallergy to?
In: Biology
As others have said, allergies are the immune system overreacting to harmless substances. It’s not really an issue of being “immune” or not. Plenty of people don’t have allergies or don’t have allergies stemming from pollen. I personally have a ragweed allergy, so I’m fine when flowers and trees are releasing pollen.
But to answer the question about why it hasn’t evolved away, it’s a mix of what other people have said about allergies not necessarily preventing people who have them from reproducing and the fact that overreacting is more advantageous than underreacting. Your immune system is capable of doing many things to get rid of pathogens. Inflammation and fever are a type of response that makes conditions harder on bacteria and viruses. If the body couldn’t do this, there would be a lot of diseases we couldn’t effectively fight off, but for some infections, the increase in temperature isn’t as necessary. And in the case of physical injury, the body can sometimes overinflame the area because inflammation helps to prevent infection and start repairing damage. But there’s a point at which those responses stop being helpful. A pollen allergy is one of those issues.
There’s also the fact that fear of allergies caused people to prevent their infants from being exposed to allergens because the scientific consensus was that it was safer that way, but we recently found out that early exposure to potential allergens while the immune system is still developing helps the body recognize that they’re harmless before the immune system is able to overreact when making threat assessments.
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