So several years back i used to take Zyrtec for my allergies, but it always gave me these huge migraines. So i switched to Claritin. Wednesday i was researching all my medications and found that Zyrtec had nothing about headaches BUT had an unknown side effect while taken with a sleeping medication. Well i was taking metformin 1 pill a night at least so that i could fall asleep at night at that time, but i don't take it daily anymore. So i'm replacing this night's use of Claritin for Zyrtec to see if i still have the headaches. Wish me luck!