I grew up with terrible allergies all my life. I started taking Claritin when it came out. It kinda worked but then quit working for me. My sister said to try Zyrtec. I took them a couple times in the morning or even middle of the day, but it worked so well at drying up my nasal drip/ running nose that it made my eyes so dry I couldn't wear my contact lenses. That really sucked so I tried a couple more brands. With no success I went back to Zyrtec. I take one every night when I go to bed after I take my contacts out. It's been a game changer for my allergies. Going from every spring with a stuffy nose and a running nose to sneezing fits where I would sneeze 10-15 times in a row, to like zero to 1 sneezes a day has been a game changer for me! I buy the generic Zyrtec at sams club. You get like 2 200 count bottles for $40. Best money I have ever spent!!