Celad (Kearney, Nebraska, Usa) on 12/01/2009:

Therefore it also works for poison ivy, oak and sumac. There was a very helpful comment about the urushiol being the active agent and once that is washed off (of everything!) the clear fluid from the blisters is not an irritant. Thankfully I just got a very mild case (through a hole in a jersey glove I think) between my middle and ring fingers on one hand. I just ran a trickle of hot tap water over it as long as I could stand it a few times (maybe I only needed to do it once ;-) and that was way hot enough to assuage the itch, again for several hours.

Getting a child to bear the heat for even a short duration is another topic!

Thank you, Earth Clinic!!