i also hate poison ivy, and also being from PA i know how big of a pain in the ass it is.
for those saying they are immune, you probably arent. if you take a poison ivy and rub it all over you and leave the oil on your skin your probably fucked, but some people really are immune. i was reading online for ways to get immunity (i mountain bike a shit ton during the week, passing poison all the time), apparently if you take some pill or basically digest some leaves during the winter months when the plant isnt around, by the time spring rolls around you should have some immunity.
i said bullshit because i feel like i would die if i had poison in my system. and i just cant trust some random doctors on the interwebs.
anyway, common myths are that if you itch the poison it will spread. Untrue- only the oil from the plant spreads the poison. So all you need to do to not get poison ivy is as soon as you get back from wherever you were, get a shower and soap the fuck out of your whole body and give it a good scrub down.