I don't know if this will help or not because seasonal allergies are sometimes different... i'm no doctor (suprise!)
I used to be unbelievably allergic to cats. Hated cats (mostly still do) and my current room mate has cats (plural) when we first started "hooking up" i would go over there... touch bottom and flee like the house was on fire... by the time i'd get to my house my eyes would almost be swolen shut and I was weezing from the cats. I'd take some claritin or that other one and it would get better. then i started taking some before i would go over there and it worked for a while and then started getting worse again.
finally it just got to be too much of a bother and I quit taking anything and was just fucking miserable, until one day I wasn't anymore. Now i can sleep with can't sleeping on my pillow with me without it bothering me. I'll still get all itchy and puffy red at the sight of the injury if they scratch me, but have no trouble with just bodily contact or respitory stuff.
my whole family (father, mother, sisters) take prescription strength allergy and antihistamine medicine to combat allergies but i don't take anything. When the polen is bad i get a stuffy nose for a day or two now, but it just goes away on it's own.