V.W.
You can take the Zyrtec before you go to bed at night to help with any drowsiness. That is when the doctor suggested my son take it. He has been taking it for months and hasn't had any issues with drowsiness. He recently switched to Allegra for a month (Dr. says over time you can get "used" to whatever you are taking and it can be helpful to switch to something else for a few weeks), but he didn't seem to have as good of control of his symptoms while he was on it. He's been back on Zyrtec for the past 3 or 4 days and his symptoms are improving again. (He doesn't get hives or itching, but sinus drainage, stuffiness, and sneezing).