I will take a stab at this one. From least drowsy, but maybe least effective to most drowsy, most effective as far as oral med go:
Claritin (loratidine) least
Zyrtec or generic
Rx Allegra (fexofenadine)
Chlortrimeton (chlorpheniramine)
Tavist (clemastine)
Benadryl (diphenhydramine)-most effective, but produces so much drowiness they use it in sleeping pills. Individuals may notice that for them, maybe Tavist is less drowsy than Chlortrimeton or Allegra is less than Zyrtec, but this is pretty close for comparisons sake.
Also remember that generic Nasalcrom (cromolyn) spray is OTC, non-drowsy, quite effective, but if it has a drawback it is that you have to use it multiple times per day. If I am into a dusty, smoky, or call it an unclean environment, I always try to saline rinse as soon as possible to rinse as many particles away before they penetrate and cause a reaction. I also think if seasonal, severe, you can ask your Doctor about Rx generic Flonase. Hopefully you have insurance and it would be a generic copay. Hope this helps, there may be other ideas also.
Mine seem to be worse this year than I remember. Anything that works, but won't make me too drowsy?