It's also known as Jewelweed. Some say it can act as a preventitive, and that by rubbing it on you before you do the yard work, walk in the woods etc... it will prevent the rash from occuring, but I never seem to remember to do that, so I can't comment on that.
The worst kind of terrorism possible is ...... getting poison ivy all over your body. I bet you that this is the terrorist secret weapon...to grow poison ivy all over the US;)
I found it in an old cookbook from my great grandmother when I was around 12. Used it ever since with success. It had lots of other home remedies and simple advice on how to dust (I learned that you should start dusting at the top of things) and be ladylike in the day (comical for todays standards). But her notes and recipes is really neat to have seen.