Hurry to the pharmacy and get some ZANFEL!!
It's a gritty soap you wash with and it works. It's high, but available over the counter. $35 when I bought mine last spring. It keeps poison ivy from coming up if you wash after exposure, and arrests it in it's tracks if it's coming up when you use it. Stops itching too.
It's a small tube but I've used it a half dozen times and have a half a tube left and I swear by it. Heard about it on Paul Harvey radio news show.