We all have our poison oak remedies. Yes, the Sarna works fairly well (for me, it only worked so-so). Prednazone takes about a day or two but definitely does the job.

But the best of the best -- for me, and I used to get tons of it spilling off my mountain bike in the Santa Cruz mountains (I had it so bad a few times that droplets of the oils would literally drip from my skin to the sink!), is HOT, HOT water. I see that Wizard also finds that to work, and I am with him. But for me, the water has to be SO hot it is almost scalding. Simply as hot as you can stand, without actually burning your skin. This method feels amazing (better than scratching the horrible itch) and yet dries the blisters. Most doctors and others recommend AGAINST hot water, because it can spread the oils. This is true. But if you use nearly scalding hot water, and make sure you run all the oils off (I use the hotest water from my bath faucet, even turning up my water heater to do the trick), it will dry the stuff out almost immediately. It will come back a while later, but with several treatments my poison oak problems used to be solved. (Haven't had it in about ten years now, because I watch carefuly for the stuff). That is, several treatments may be necessary but believe me, they feel great as you are doing them.