As someone who has suffered from hay fever for my entire life, and also lived in many different locations, almost every move came with a 2-3 year reprieve from my symptoms while my body "discovered" the fun new local allergens.

It’s known that repeated exposure to allergens can cause allergic symptoms in people previously without them. For example https://en.wikipedia.org/wiki/Bird_fancier%27s_lung https://en.wikipedia.org/wiki/Farmer%27s_lung

I actually seemed to grow out of hay fever when I was in my early 20s. Perhaps coincidentally this is also around the time I developed an allergy to cannabis from overuse. Wonder if they’re related somehow.

Yes. I developed hay fever after living here in Japan for a couple years. Was fine the first few years, though it was amusing to watch "yellow clouds of pollen" being blown from the trees with random gusts of wind. Now it's not so amusing. My car windows are dusted with a new layer of "light yellow" every couple days now (in season).

Lots of people I know who moved here as adults have developed pollen allergies over the years. Some after a 2 or 3 years, some after 10.

I got hayfever on my 3rd year of living here, and it seems like quite a common pattern among immigrants I've noticed. I have hayfever back in the UK too, but I guess I didn't have a Cedar allergy - so it took time to develop.

I have been living in Japan for almost 8 years now, and I didn't have any allergy ever until a month ago when all of sudden it hit me like a hammer. Good god was it painful...

I'd been wondering why my allergies go nuts every time I visit Japan, but never really suffered in other Asian countries. Cool to know now.

Upside is I discovered the trick of just taking fexofenadine every single day which had the side effect of solving my chronic sinus infections.

I would assume it has more to do with less exposition to hay/pollen in urban areas, for instance in years in Beijing I've had hardly allergies since it is not exactly green, though I went to parks, but here in Prague right now with everything blooming it's nuts.

Actually now that I think about it never head really problems with allergies even in Southeast Asia, though I was in very green areas, maybe humidity helps as well?

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