According to a study published in the April issue of Annals of Allergy, Asthma and Immunology, Benadryl appears to be more effective than Clarinex in relieving symptoms of moderate to severe hay fever.

"Benadryl provided significantly better overall allergy symptom relief than Clarinex," investigator Dr. James T. Angello told Reuters Health. "Even more noteworthy in this study is the finding that Benadryl relieved nasal congestion just as well as it reduced allergic rhinitis (i.e., hay fever) symptoms as a whole."

Downside: Benadryl caused more drowsiness than Clarinex.

Read more from the Reuters report: Benadryl edges Clarinex for hay fever.