Allergies

Do allergies just suddenly appear at some point in your life when you've never had them before? Growing up I never had allergies (other than to one or two pharmaceutical products). As an adult, I'm sneezing my everloving head off every day it's sunny out. I can't understand how my body could just suddenly decide one day in my late-20's "I think I'll decide I don't like pollen any more".

I feel like a little kid crying "no fair!" because now that I'm finally old enough to have a nice convertible and great weather, I can't really enjoy it (because I HATE taking drugs).