Levocetirizine, the R-enantiomer of cetirizine, has been found to be less sedating relative to placebo than was cetirizine in separate trials. We plan to examine whether patients who did not tolerate cetirizine due to sedation are able to tolerate levocetirizine. This study will utilize a randomized, double-blind, placebo controlled trial comparing levocetirizine, cetirizine, and placebo in regards to sedation and allergy symptom scores. Each patient will receive levocetirizine, cetirizine, and placebo in randomized order and thus serve as their own control.