As a hiker/flyfisherman, I regularly encounter poison oak/ivy. Also, I am HIGHLY allergic to it. After years of experience, if I know or suspect I have come into contact with it, I get to water as quickly as possible and use the flowing water and river sand/rocks to scrub the site. Years of doing this without any outbreaks. I think the time you have to get the oil from your skin is 15 minutes, so there is a little buffer.
How To Recognize and Avoid Poison Ivy