What Causes Itching All Over The Body While On Celexa?

I have been on Celexa (generic brand) for many years. Can you become allergic to a medicine after being on it for so long. I have been itching all over since the end of Sept. Have been to the allergist, GP, dermatologist and no one can figure out what is causing it. I have not changed any detergents or anything like that. It doesn't want to go away so I thought maybe it was one of my medicines I take daily. My GP has taken me off of my Crestor and Celexa and I'm still itching. Do you have any advice you can give me.
Miserable,
Carol