Zyrtec is the only allergy medication that I have tried that doesn't cause drowsiness and actually keeps all of my allergy symptoms away for a full 24 hours.  Without Zyrtec I would have red, itchy, watery eyes anytime I stepped outside or came near a cat.  There would be sneezing and itching around my nose and an occasional sore throat. 

The small size of the tablet makes it much easier to take on a daily basis along with my other medications.  I have also found that the store brands of Zyrtec work just as well as the name brand, saving me a great deal of money each month.