I am taking vicodin for a week. just last night i was itching all over. any relation?

Possible reaction: Itching is seen with use of many pain meds. If you do not have a rash or notice any breathing issues it is simply an annoying side effect. If you have rash or and thing more than just itch you need to stop medication.

Histamine Release: Many patients have a symptomatic release of histamine with opioids. Different opioids(narcotics) vary from patient to patient in how much this affects them.Why are you taking the vicodin for a week? You might try another opiod.This is generally not an allergic reaction but a side effect that is common.