Jewel Weed (Impatiens carpensis) grows in the same habitat as poison ivy. The late naturalist Euell Gibbons touted this plant as a cure for poison ivy, if you apply the crushed stem juice shortly after being exposed to PI. Gibbons would harvest the Impatiens c. stems and plants, mash them up, and freeze the juice in ice cube containers, then bag these in the freezer for later use.

http://www.altnature.com/jewelweed.htm


Once the blisters develop, it's too late to prevent them, but if you can relieve the itching pain, you won't suffer and you won't be tempted to scratch. So the condition will heal in optimum time.

Someone online sells a simple and inexpensive electric gadget with a metal plate about the diameter of a quarter. This seems to be an ionizer of some kind. You run the plate over the blisters and there's a zapping sound and feeling. Lo and behold, the itching subsides and you won't feel it again for quite some time. I used this after planting seedlings and scooping dirt from the holes with my bare hands and forearms (a really stupid move). Results: worst case of poison ivy ever and many days of dripping, oozing misery until I found out about this electronic gizmo.

I can't find the website but the device sits on my desk right now, it has a plastic formed, rounded handle with a switch on the side. About eight inches long. Sort of a 1950's futuristic looking profile to it. There is no label or identifying mark from the manufacturer on mine.
It didn't cost too much either, as I recall. There was a website.

Similar product with a push button Piezo-electric working is sold in the UK under the name, M-Zap. Cost about 6 pounds. The American one plugs in to the wall, with an AC adapter. One reviewer on Amazon.uk says:

"I don't know how it works. I suspect it locally depolarises and 'switches off' sensory receptors in the skin, which stops the itching and thus the scratching. I think the lack of scratching is what makes the bites heal more quickly."

I think he's right. It also relieves the sting from bug bites, etc.