Rich,
I don't know how barrier creams will work for woods, but I use an Ivy-block for poison ivy.. I'm highly allergic or sensitive to it and just the thought of it can make me breakout in nasty runny, weeping blisters. The ivy block seems to work about 98%, but I'll still get a spot here and there that I might have missed when I put it on. I always wear long pants, long sleeves, high boots, etc when I know I'll be working around it. So far this summer, I've avoided any serious outbreaks.
For the wood barriers, I would think that short of having a tub of it and being able to completely submerge your body so as to cover everywhere, you could still have some problems... the dust floating in the air can settle on you and will cause a problem.
I've moved to using a smock when I turn, zipped and wrapped to the neck... seems to have helped some for me. I don't use gloves, except for a cut-off leather glove on the left hand when I'm hogging wood off a new piece... the wood chips were beginning to hurt and skin was sensitive to them flying against the back of my hand. I've still had to pull Paduak from my shop.. (knock on green wood (the side of the head)) so far that seems to be the only wood I am sensitive to. Also I've careful to always use either a mask or a respirator. As everyone has said and has cautioned me a wood sensitivity is not fun. So far all I get is a pretty nasty rash, but I don't want to go any further if I can prevent it.