Yes, it happens. I got a terrible case of poison oak over ten years ago after bushwhacking through heavily poison oak-infested terrain. After a couple weeks of misery, I was put on steroids, which cleared it up. But every few years I get a recurrence completely independently of any re-exposure. I mean, it is impossible that any re-exposure has occurred, no question. The flareup starts on my inside left arm and may proceed to my right arm. So far it hasn't been as bad as the initial bout. Weirdest thing. But real.
