Good morfnoevight you hold out stoners!
Immunity to poison oak can be temporary or you can be sensitive to different "strains". I have walked through patches without incident but I got a little root juice on the back of my hand prospecting that caused a reaction. I did not know what it was at the time so I went to my Doc, he identified it as poison oak. He explained it to me as all about the degree of exposure: Walking through dry plants transfers mainly pollen which sets off some people, wet from dew is bad on skin contact and the juice from the plant is very potent. Even though I don't react to dry contact with poison oak I walk around it now.