Welcome Stay! I'm sorry this happened to you. It could be the specific generic of Percocet that you're allergic to, and not all Percocet generics (and not brand). Also, yes, I think it is reasonable and logical to switch back to the Vicodin, and not be left without. Did he switch you because the Vicodin wasn't strong enough? Could he have upped your dose instead? How much were you taking and what strength? I know, 20 questions.
I think the thing you need to make them understand is YOU'RE STILL IN PAIN!! It has nothing to do with the withdrawal issue, because it's not time to deal with that!! You're in pain, and that's that. You need some medicine that helps. As long as you're in pain, you're going to need meds, and for them to "all of the sudden" tell you to quit taking them is unacceptable. You didn't call them and say, "I'm feeling better, and I no longer need pain meds." You called and said you had broken out into hives...that means, "I still am in pain and therefore NEED meds. Hives has nothing to do with my need for meds." I would raise holy cane until I got a script for something that works!! This is ridiculous.
I'll be praying for you, and I hope you "stay", because the people on this board are awesome.

Let us know how it goes. Girl, stand your ground.