I had it when I was too young to remember. I used to live by this huge patch of it when I was young, and I didn't know it was Poison Ivy. When I was ten, I took a match and lit the patch on fire. I felt like I was going to die from breathing in the Ivy (and Oak) fumes.

Also, Poison Ivy is contagious if you deliberately rub up against someone with an open, infected sore.