I get poison ivy EVERY YEAR no matter how much I try to avoid it. This year I got some on my eyeball. Yes, it was as bad as it sounds.
Avoiding? It's hard. I treat every woodland outing as a tick/poison ivy exposure, I use Burt's Bees poison ivy soap (coal tar based) to wash up and I KNOW it works when I KNOW i've contacted poison ivy and wash within 20-60 minutes. It's when I don't notice that I get it. It's EVERYWHERE around here, and you can't always avoid it.
At the moment I have a small patch of poison ivy on my left calf and ankle. That's exactly where the 4 yellowjacket wasp stings were delivered about 3 days ago.
Fels Naptha soap works too, but really, nothing works for me AFTER the rash is out - I just ride it out.