Put vaseline up your nose, its not very lady like, but it is very very effective {it catches the pollen}, also wearing wrap around sunglasses ''WILL'' assist in stopping the pollen entering your eyes, early morning & dusk are the most vunerable times apparently for sufferers of hay fever.
Ps, at least you can go out when it rains, the rain dampens down the pollen, shower as often as possible as well, this will assist in getting rid of the pollen on you, other than that, chazza has probably covered every other base, don't pay over the odds on brand names, look to see if they have cetrizine as pointed out