if the allergy is pollen (seasonal) dont forget they make hepa air purifiers, even in a huge model. sometimes you might have to stay inside, even right next to the thing.
if your allergy is more common year-round (mine is mold), the air purifier and some serious environment evaluation might be key.
also try the zirtec, i notice no sleepiness from antihistamines, even took them once in awhile to stay awake.