I've read that water deactivates the oils from poison ivy so if you wash it as soon as you contact it, you're alright.
I would imagine that most "spreading" is caused my multiple contact with contaminated articles.
I don't think water alone does. You need some type of soap. In fact, if you use bar soap I imagine you could get the oils on the bar and spread them that way. Probably should use liquid soap in the shower.
Also, I get it really bad and remember taking a bleach bath at times to help dry up the stuff. Maybe that's why I'm so white!
