Yes ... this one. I have grass allergies and always suffer more when I visit Oregon.

THIS. The only places in Oregon where my grass allergy is controllable is the coast. I also risk going into Tillamook for the cheese factory.

Huh. That's really interesting, thanks for the answer Tom.

Funny thing is that I never have any allergies when I cut the grass in the backyard at home. Do you think it's possible that I have a grass allergy, but there's just not enough allergen in my backyard to trip the switch, but the massive scale in the Willamette Valley sets me off?

I am asthmatic and allergic to nearly everything except dust-mites and, thank god, dogs. Cats have quite literally almost killed me.

I asked my wonderful pulmonologist the same question. He said, iirc (it was a while ago) that there could be several factors at play.

He likened my allergy response to having a glass of water. Once the glass is full and overflowing the allergic reactions start. What fills the glass is, of course, your allergens.

When you are mowing your grass you are being exposed to a fair amount of allergens but unless you let your grass get so long that it begins to manufacture pollen you are being exposed more to what pollens are being kicked up with the dust caused by the mower. In addition, it is usually a one-time brief exposure. If the ambient pollen load is not high then that exposure may not be enough to fill your glass.

Sod farms don't just grow sod for harvesting. They also grow grass seed. I understand they also hybridize grass types by dumping mass amounts of pollen on tall farmed grass from planes but do not know that for sure.

Regardless, the end result is a constant exposure to a fair amount of ambient pollen. Your glass never gets a chance to drain. Eventually it hits a critical mass point and you're suffering. And it may not stop for a long time.