I got a poison ivy rash, from weeding. It got annoying, so I bought a white boletus mushroom, shaved the stem into a mix of hand sanitizer, dish detergent, and hydrogen peroxide 3%, and mashed it up well; rubbed it thoroughly into the rash, rinsed, put more on and let it dry. The swelling started to go down in only minutes. Three hours later, it doesn't itch at all.

I gather that in Japan they make lacquer out of poison ivy sap, polymerizing it with enzyme from shelf fungus.