I came across this article a few days ago. The comments are hilarious, including several links to medical articles stating exactly what M'Sharak said.
I knew a child who takes regular medication because simply being around oak trees at certain times of the year could trigger anaphylactic shock (this was several years ago and I can't remember exactly what triggers the allergy, only that she was "allergic to oak trees"). The child's mother, a nurse, made sure the child always took her medication, always had an epi-pen on her, and sent the child on her merry way outside to play with the other children. No way in hell did she expect a single tree that wasn't on her own property to be cut down, even though in this rare case being around an oak tree really could kill her child. The child was four years old when the allergy suddenly developed, and from that age she could recognise an oak tree and knew to stay away from it.
That's pretty interesting, what were her symptoms when she was around the trees? I'd be looking at moving somewhere where these trees were uncommon, though that might be counterproductive if slight exposure over the years build up the body's resistance to them. And I suppose there are whole countries where you'd be stuffed as far as no oaks went.
If I remember correctly, the child wasn't directly near a tree the first time the allergy kicked in. She did well on her medications, and, to be frank, it's difficult to avoid trees in the Canadian province of Ontario. As the child does well on her medications there's no need for the family to move to the prairie provinces or above the tree line.