We grow some serious poison ivy here on Winterberry Farm. Not purposefully of course, but it seems to favor the soils, air, and moisture on our land.
Some of the plants are the orangutans of the vine world. The orangutan, though, is a much more gentle forest creature compared to poison ivy. The leaves, stems, fruits, flowers, wood, and those copious red root hairs all can cause a nasty, itchy rash, red bumps, and blisters.
Some people say they get a rash just by looking at the plant. But, only direct contact with the plant can cause the irritation, when the oil is absorbed into the skin. Poison ivy (Toxicodendron radicans), along with poison sumac and poison oak, contains urushiol oil, a sticky, resinous substance that remains active even on dead plants or even becomes airborne from lawnmowing, trimming, or burning.
Now I always say that I rarely get poison ivy. I work in and around it a lot (clearing brush -- really). When I come inside after such a day, I wash well with warm water and soap. This has worked well for me. On a rare occasion I will break out in a small rash, for that I use calamine lotion. Still, I wouldn't go hug a tree with one of those thick vines. I like the saying "hairy vine, no friend of mine."
Some recent research indicates that poison ivy does better under increased CO2 levels. Just great. I am not in favor of torture, but I could envision some pleasure seeing climate change skeptics spend time barefoot in a patch of glistening poison ivy. For the rest of us, remember -- "leaves of three, let them be."