If you get into the stuff, and haven't exploded in a rash yet, there's a soap called "Zanfel" that is really good about getting most of the oil off of you. I get systemic reactions just about everytime I get exposed to ivy, and the soap immediately afterwards is a lot more fun than the doctor's visits and shots and steroids and all that.
I was clearing some brush once, and stopped to take a leak without washing my hands. I'd been wearing gloves most of the day, so I thought I would be fine. The next two weeks were two of the worst weeks of my life...