I found this thread on Native plants http://davesgarden.com/community/forums/t/884446/ and thought others might be interested. It says that Jewelweed Impatians capensis is used to treat Poison Ivy.
MED: Poision Ivy Treatment
Jewelweed is absolutely wonderful for poison ivy. We make a spray that works wonders for the itch of it.
Interesting! I'm in NY right now and we have had poison ivy in some places on our hillside. We've managed to get rid of most of it over the years but some remains. We've always had jewel weed growing very near the poison ivy. I never knew it was so useful as a remedy. I once got poison ivy after sliding down a bank to a river in my bikini. You can just imagine the places where I had the poison ivy. Wish I'd known about the jewel weed remedy back then. I'll certainly remember it in the future but I avoid poison ivy at all costs since then!
Momherb! Oh, ouch! I find it interesting that jewelweed grows so close to the plant it remedies. Break open the stems and apply the juice to the poison ivy rash. Do so as quickly as you can after getting the PI rash. Don't burn the poison ivy in an attempt to get rid of the plant. If you breath that smoke in, your lungs can get the rash. Then you are in deep water.
BTW, I enjoyed meeting you!