allergic rhinitis
"Zyrtec knocks me out. Period. I took a pill at noon and by 2:00 pm I lay down virtually passed out. I slept for two hours straight. In the middle of the day. When I awoke I could barely function. Brain fog, lethargy, no energy. To tell the truth, I was so spaced out for so long that I couldn't tell if helped my sinus condition or not. I wouldn't dream of taking it if I had to drive. It would make a great sleeping pill."