As someone who made the opposite move (Bay Area -> London) I found that I started suffering from hay fever for the first time in my life.

I think that any move to an area with a sufficiently different mix of pollen can cause problems for your immune system.

Some years ago I moved from northern Norway to central Dublin. By any reckoning that's a decrease in air quality -- though Dublin is still much better than most cities -- but it also came with a reduction in allergic reactions.

I suspect simply because there isn't as much nature in the vicinity, which I don't actually appreciate. Oh well.

As someone who has always lived in London, I started getting hayfever around age 22. When asked by doctors if I have any allergies, and I say nothing except maybe hayfever, they always say "oh everyone has hayfever"

Its commonly not allergy e.g. not a histamine response. It can be simple irritation due to particulates in the air. Everybody should respond to that.

Pollen could definitely be a key part of it, but I doubt it's the whole story. Checking the PM 2.5 count for yesterday for the Bloomsbury sensor in central London, it's actually about 70% of that at any of the sensors in the East Bay (Berkeley, Oakland, etc) or San Francisco.

http://www.baaqmd.gov/about-air-quality/current-air-quality/...

You need to convert units, because the US readings are given on the AQI scale, whereas the London ones are raw measurements:

https://aqicn.org/calculator/

Especially in the Bay Area. There's a reason sour dough bread is a thing, for example. It's in the air.

Wild yeast is in the air everywhere. Sourdough is a thing in SF not because the environment there is particularly good for it, but because of historical reasons (ie, French bakers moving in during the gold rush).

>Wild yeast is in the air everywhere

But not the same yeast everywhere. Plus bacteria are also a factor, and also vary place to place. Some may cause worse allergies than others, depending on the person.

As far as I know, French bakers didn't bring the yeast (or starter) responsible for sourdough. They just brought french bread. The sourdough part happened naturally, at least initially. Now it's actively encouraged.

But even with the right starter, the further east you go, the harder good sourdough is to make.