I've heard that if you ingest the leaves of poison ivy, starting with the new growth in the spring, you will get some immunity for almost a year. The mucus in your mouth and stomach is sposed to protect you from the oils that hurt you on your skin. I have never done this and there is a trick to the timeing of when you gather the leaves, how often you injest them and the like. I wouldn't try it without researching it on your own to find out more, but its something interesting to think about.