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Comment by rhinoceraptor | Hacker News Reader

The hygiene theory also doesn't make 100% sense to me, I had no food allergies, no pollen allergies or asthma as a kid. Then in my late 20s, I got an egg allergy bad enough to require an epipen, as well as seasonal allergies, both out of nowhere.

I used to eat eggs several times a week, and now I have the type of egg allergy now where I can't even eat baked eggs, so no muffins, brioche bread, cookies, etc.

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It's probably a bit of one, a bit of two. Despite spending everyday in the garden growing up, I've always struggled with allergies and they've changed throughout my life. I was deathly allergic to tomato's and eggs as a child but grew out of it around 11-12, became very allergic to pollen and pet dander at 5, which is now life long, and recently in my late 20s become allergic to hazelnut and some other foods I've yet to pin down (my mouth comes up in hives with no rhyme or reason while eating occasionally). I've also developed oesophagitus in my late 20s, to the point where I choke on foods daily unless chewed to a pulp before swallowing.

To me, it seems the parasite theory makes sense in tandem with hygiene. Some people by upringing become predisposed to allergies, while others have genetically as a result of humanities constant fight against intestinal worms. As our genetic profile changers as we age, so does how our bodies express said genes which would be designed to fight something we no longer have.

The immune system is a complex, only partly understood system, and there isn't a single unifying solution to all of its edges. Broad understandings don't necessarily translate to individual cases.

At some point your immune system faced an adversary and conquered it, but one of the signatures it learned from the enemy encounter unfortunately also matches some molecular component of eggs. There is evidence that some people come out of norovirus infection with an egg allergy, for instance. Similar to how a bite from a lone-star tick can give you a meat allergy.

All sorts of auto-immune diseases can be kicked off by relatively benign things, and often we might never discover the cause. Our immune system learned the heuristics of something, but it's too broad so ends up looking too much like our thyroid glands, nerve myelin, pancreas, etc.

Maybe one day we'll be able to enum all of the signatures an immune system has learned and delete some of them.

The hygiene hypothesis is mostly for childhood allergies and even then it wouldn't explain everything. Here is a counter anecdote: my sister has some skin allergies but I don't. I was allowed to play outside and used to just run around in my backyard and my neighbours. Those places can be pretty muddy. My sister was not allowed to and she has allergies.

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