Poison ivy is only contagious via touching for the first 45 minutes or so after you are initially exposed to the oils of the plant. After that the oil soaks into your skin and cannot be transmitted. So pretty much, if you already see blisters or are starting to itch, it's probably passed the 45 minutes. Unfortunately, if its before you know you have it, you're just out of luck. I'd suggest washing your hands anytime you've been outside before handling the chins.
I'm horribly allergic to poison ivy, besides having just the local skin irritation, so I've done a lot of research on the evil, evil stuff.