I have really bad tree pollen allergies. Mine started about 2 weeks ago, the first warm day where there was a wind from the south. I've tried Claritin, Allegra, Flonase, and Zyrtec. Flonase works the best, but it only last about 2-3 hours and you're only supposed to use it twice per day. Zyrtec makes me drowsy and doesn't relieve any symptoms as far as I can tell. The best success I have had is with a pill combined with a nasal spray. Today was not a good day to test allergy medications, I didn't take anything today and had no problems, the pollen count was probably really low (they only measure on weekdays). When the pollen count for trees is "high" or "severe", I have never found anything that works effectively. Thus, my conclusion is that the best allergy medication is rain, because it washes all the pollen out of the air.