It is very unusual for someone to have allergies, of any kind, if they come from a family that contains people who aren't allergic to anything. So yes, though it is not necessarily allergy specific, the genetic tendency is usually there.
Then there is the dramatic climate/geographical change. This is, for the most part, pollen related. People who either move to a different continent/ completely different part of the same country, usually WILL wind up having allergies to pollen/plants/trees; even if and when they move back to their original place of birth.
Exactly what happened to me when I moved from NYC to Delaware.......had no clue what was going on, thought I had some kind of a major disease.
It's been an interesting discussion, but this has been a long, and right at the moment unhappy, day and so I will bid you all a fond goodnight. I expect this will get picked back up in the morning :)