I used to be one of those guys that "never got it".....UNTIL I GOT IT. Now I can't even be around the stuff without it showing up somewhere on me. Truly sucks more than many can ever imagine.
The worst I ever had it, I was cutting wood with a chainsaw and burning underbrush. It was raining and everything was dead (brown), or so I thought. Apparently from the combination of ivy oil and water seeping through my clothing, the fire smoke containing contaminants I was breathing in and the number of times I stopped working to pee (yup, you guessed it), I ended up with poison ivy and oak together on a majority of my body.
I had a shot and went through 2 10 day treatments of prednisone before it actually cleared up. All told, I had a severe rash for a little over a month and noticeable marks for at least 2 months.
My second worst time, the reaction was centered solely on my hands. I shot two rabbits that had apparently bathed in poison ivy oil. While skinning them, I of course got the oil on my without my knowledge. A few days later, my hands had tripled in size and you could not see any daylight between my fingers due to the amount of fluid present in them. Luckily, no peeing that time.
In short, avoid it. It sucks.