I guess I'm one of the lucky ones then. I'm 46 years old and am exposed to that stuff all the time. Never had a reaction. Friends of mine have had severe reactions helping me clear woods, weed eating, etc, so I know I got plenty on my property. I often pull it down off trees with my bare hands, and/or cut down trees covered it in and burn them.
After reading about the dangers with burning it, I will stop that practice however. If not for me, then for the rest of my family & friends that might be around.
Back in Denmark where I was born and grew up, we had a plant called "Braendneller". Touching the leaves of this plant would result in a bad rash/blisters. It would actually start hurting within seconds of touching. As far as I know, nobody is immune to those suckers. The "Braend" part of the name of the plant translates to "burn" which is the sensation you get within seconds of touching the leaves.
What actually happens is that the leaves of the plant contain a toxin, and the walls of the leaves are like tiny "glass" hairs, and at the slightest touch, these hairs will break, leaving a slanted sharp edge that will easily penetrate the skin and empty the toxin, which is what causes large number of fluid filled blisters to form.
Interestingly enough, the toxin is not fatal, even in large doses, but is sure is uncomfortable! Some even grind up the leaves and make a soup with them then that supposedly can have medical benefits.
Here's what the plant looks like in case you ever plan a trip to Scandinavia that includes hiking: