Allergies are a big problem for a lot of people. If you're someone with pollen allergies, maybe you've wondered how people in the distant past dealt with them. After all, a thousand years ago people mostly worked outside all day, in areas where plants grow well. They had no air purifiers, no allergy medication, and no extra food for people who couldn't work when it was time to plant crops.

The answer is, pollen allergies just weren't very common back then. There was a massive increase in their prevalence from about 1850 to 1950. Here's a paper noting that.

the hygiene hypothesis

That paper argues that the increase in allergy prevalence is due to increased hygiene. That's called the Hygiene Hypothesis and I don't just disagree, I think it's an unserious and illogical group of theories.

First, let's keep in mind the basics of how the immune system works. An immune response to some target develops when the target is present at the same time & place as harm or a known-harmful substance. Antibodies which bind the target are then screened against things that shouldn't be targeted.

Now then, the Hygiene Hypothesis refers to [...]

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Outline:

(00:45) the hygiene hypothesis

(04:19) a note about references

(05:33) air pollution

(08:02) food allergies?

(08:18) can this be solved?

(10:52) conclusion

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First published:
May 18th, 2026

Source:
https://www.lesswrong.com/posts/eEkWgddYQ3xZGtQDP/why-pollen-allergies

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Narrated by TYPE III AUDIO.