I think the humidity has to play a role in that. Very dry air is not good for the nose even without allergies. This year the spring is very dry and also quite cold in Central Europe which makes things worse.

In Japan, however, it's almost always very humid. Today, for example, it's over 70% relative (when the sky was still clear and mostly blue, now it's raining so it's much worse). And, as said in that article, there's a lot of allergy in Japan. My wife (native) has a little bit of it, and I myself also reacted for a while, but given time it seems to have left me (as I mentioned elsewhere I grew up on a farm with exposure to everything and I never had an allergy before).

There's one guy I know who lives more or less in the middle of a forest with both Sugi and Hinoki, and he's suffering a lot. But he still likes it much better there than in the huge city where he grew up. I noticed that among the locals in that place (just a bunch of houses, not even a village) I didn't see anyone else with that kind of allergy.

> In Japan, however, it's almost always very humid.

Yeah I realised that's a little bit of an issue in my theory. Of course if it's very humid I would also expect that most buildings have aircon that's keeping the humidity down and can contribute to the allergies.

Buildings, as in large buildings, maybe. Homes don't use that much aircon. We actually never do, except if we have guests, and in any case it's never used the way I experienced so often in the US - that it's actually cold (and very uncomfortable). When used in Japanese homes it's used sparingly. There's also typically a "dehumidify"-only setting, but that's mostly a losing battle, what with the house being surrounded by humid air (and until very recently even new homes were far from airtight), so mostly you just live with it.