What Dan said.
Here are some other related threads:
No Poison Ivy in Mexico
Plant of the Week 22
My old business partner, a guy and I gutted a weedy Kettle Moraine sand prairie many years ago, only to realize at the end of day 1 that it was chock full of poison. We had been pulling out rootstock barehanded in the hot September sun.
I got a mild case of scratching, the old business partner got what he deserved, and the guy, he was completely lit up, oozing blisters covering arms, knuckles and between fingers, and over most of his face. There were two experienced plantsmen on the job, and the guy wasn't one of them.
Yeah...he got the week off.