I think this myth might stem from people not getting hayfever, moving away from where they grew up, and then suddenly getting hayfever and attributing it to where they moved to. But the truth is it just can be (frequently is I believe) adult onset (20s very typical I believe).
At least, that was my experience, I blamed Cambridge, then moved back or even when I visited before that had it just as bad in the town I grew up in. (Cripplingly painful eyes, sometimes migraines. Nose generally fine, but steroidal nasal spray is the best I've found off prescription for my eyes. Eye drops only really seem to help by way of lubrication for me (even though they are active), and pills (best I've tried is fexofenadine) don't give that instant relief.)
The only time in my life I've ever had hay fever was when I was 15 taking a summer program in Oxford. I'm from California. Never had hay fever again. I think I'm just allergic to England.
At least, that was my experience, I blamed Cambridge, then moved back or even when I visited before that had it just as bad in the town I grew up in. (Cripplingly painful eyes, sometimes migraines. Nose generally fine, but steroidal nasal spray is the best I've found off prescription for my eyes. Eye drops only really seem to help by way of lubrication for me (even though they are active), and pills (best I've tried is fexofenadine) don't give that instant relief.)