Well, according to this post (scroll down a bit) on a search & rescue blog, some people are convinced that eating a tablespoon of Certo per day will protect you from poison oak. Or, if you're already suffering from it, two T. per day will alleviate symptoms.
I've been fortunate in never having reacted to poison oak, but I'm wondering if anyone else has heard about the Certo trick. Is it snake oil or legit?