Xyzal
"Xyzal is one of the most effective antihistamines out there, IMO.  It stops all my allergy symptoms from the first pill- I can feel my sinuses open up.  It has gotten me through horrible seasons where the grasses I'm allergic to are rampant.  The only downside for me is the major sedation.  It is supposed to be non-sedating, but a few people will have issues with this.  Curiously, I find the sedation to come on several hours after I take it, so I time that with bedtime.  At first the sedation was so bad that it felt like I was going under anesthesia!  My allergist told me she had the same issue, and had me cut the tablet in half to take the pediatric dose.  That helped a lot, but I still time it for when it makes me tired."