Why do my pain pills make me itch?

I was diagnosed a while back with chronic pain syndrome. I usually take celebrex and vicodin for the rough patches. I have taken vicodin for years off and on, and experienced the itchy nose but nothing as bad as this. After my second dose of this new script, I itch all over. even my scalp feels itchy. I have never had this as a widespread condition, just my face and nose sometimes. Can anyone tell me why this new script has this side effect? and what can i do to tame the itchies? I have tried lotion, benedryl, chlortrimeton, aquaphilic, i recently started on valerian for sleep and anxiety. is it possible that this is what the problem is? I am a clean person and my house is most of the time, very clean. is it just dry skin maybe? id appreciate any advice.