Benjamin, I might suggest a different route. Studies have shown that intranasal steroids (like Flonase) work much better at preventing the symptoms of seasonal allergies than antihistamines. Granted, you need a prescription, but that is a small price to pay (assuming you have insurance). Claritin, Allegra, Zyrtec all work at treating the symptoms, but an ounce of prevention is worth a pound of cure. If you are still having issues, and cannot take intranasal steroids, then I agree that Zyrtec is most effective (but also most sedating). You might also try taking Benadryl at night, since you are going to be sleeping anyway. That way you sleep better and don’t wake up with itchy eyes and that “beat up” feeling in the morning.