No one is immune forever, there will always be cases of ivy problems. Many a ranger explained that one to me when we would be camping in the woods with the boys scouts. One year it was so bad on long island, that the camp area we went to had all 3 main varieties of the stuff, we made the boys chant though the woods, leaves of 3, leave them be until they would inspect every area they went into before they got into trouble. We had Ground, Bush and climbing. He said that some people will not always have a reaction, but that doesnt mean you never will. When we helped my son on his Eagle project, which was to clear out an area of garbage, overgrown stuff and dead trees so we could plant new ones 10 years ago, we got those environmental suits donated to us. Even if not donated, they were not horribly expensive, were not hot to work in, and you threw them away at the end of the day. We had massive poison ivy to go through, and no one had a problem. It is sort of nylon fibrous paper. Strong, although you would not have thought so when you saw the suits. Everyone who worked in the ivy area had to don one, made a big difference-it even covered your shoes. If you guys are encountering it in the trees however, I dont know how wonderful it is to climb with. We were also encountering poison oak, nasty stuff as well-and it did not get through these suits. As only the climing stuff gets into the trees, it is usually the most intense, at least that is what I found here.