The short answer: Once the poison oak resin, called urushiol, gets onto your clothing, boots, or poles, it can stay there for months.
My question is, how can you be tromping through the stuff all day and not yourself suffer from the effects? Poison oak is one of the most insidious plants out there. Its resins literally bind to human protein, causing a vicious allergic reaction and weeping rash that can completely debilitate some people. Treatments are mediocre at best聴cortisone creams seem to help聴and there are also skin creams that repel the urushiol. They’re called Ivy Block and StokoGard Outdoor Cream. Both form a barrier over your skin that the urushiol can’t penetrate.
How to clean your clothing and boots? Ordinary soap won’t do much good聴the urushiol is chemically a little like pine pitch, so soap just bounces off. Still, hot water, a little extra laundry detergent, and two washes should do a pretty good job on clothing. On boots and other items solvents work best, with ordinary rubbing alcohol a good candidate.
Obviously, your best policy is avoidance. You know what the stuff looks like by now. It tends to grow along oak and other tree trunks, or in thickets of chaparral. So, keep bushwhacking to a minimum and don’t use ivy-covered tree trunks as a headrest during a break.
Poison oak is no joke. Hundreds of California firefighters get covered with the stuff each year, and are forced to leave work for days until they recover.