actually, the best, and most painful treatment I've ever found for poison ivy is almost free.
It stings like hell, and it works perfect.
Dillute, I repeat, DILLUTE, a bowl w/ 1/4 bleech and 3/4 water. Make the water warm.
take a brillo pad....(not the metal ones...but a fabric one)....and run it under as hot as water as you can stand. Run your body part under the same hot water till it turns red. in my case, I got it like hell over my arms.
Take the brillo pad and scrub it hard.......but be careful to not make it bleed. there's a fine line.......just wanna make it hurt a little bit. if you get too deep, the bleech will make you scream.
Then rinse off w/ some cold water.
Last time I got infected, it was poison oak actually......and I did this treatment every day. It hurt like hell, but fter the treatment, I waas good to go....without a single damn itch for about 8 hours.