Just wanted to make sure you didn't recently begin taking some sort of vitamin, such as Niacin. If you take too much Niacin, you can get "flushing" and also terrible itching if the Niacin disperses too fast.
I take medication for high triglycerides that has Niacin in it and that it a side effect. It drives me CRAZY when it happens and NO amount of Benadryl will help because it's internal.
Good luck and I hope you feel better soon.