allergies
"I feel absolutely horrible.  I ran out of Zyrtec, my son takes this so I figured I'd try it.  On day two I feel a combination of having a concussion and a hangover all at one time.  I'm fatigued, dizzy, and have a headache. This does not include the pressure I feel in my sinuses.  I feel absolutely horrible.  I'm done, I won't take this again.  I'm honestly not even sure the FDA should have approved this drug."