No one is immune to PO/PI/sumac. When you are exposed repeatedly at some point you hit the threshold and start to react to it. I haven't yet gotten a rash, which is why I'm extra careful about not getting into it; I want to preserve my "immunity" for as long as possible.

Poison Oak
_________________________
"In the beginner's mind there are many possibilities. In the expert's mind there are few." Shunryu Suzuki

http://hikeandbackpack.com