TecNu works pretty well. I don't know of anything short of amputation that "CURES" it once you have it.
TecNu works best if you treat right after exposure. But, in cases wear you don't know you have it, and the rash starts, TecNu is like Cold medicine, in that it relieves the severity and the length of time you have the rash. Bendryl can also help as a supplement.
I have gotten a lot of Poison ivy/Oak here in the Mid-Atlantic region (and still get it) and TecNu is my go to snake-oil. You have to read the directions for use, regarding rubbing and the use of hot or cold water, and follow them specifically, it does make a difference.
for After Rash treatment I use Hot water, as Hot as I can stand. Then I use Isopropyl alchohol for it's drying dessicating effect, then coat with Caladryl lotion. It turns it from out-of-your mind itchy, to bearable. I think it also help your skin recover more quickly, and the rash subsides faster.
I support what Doc is saying. My buddy is immune, or pratically immune, he can roll in it and pull it off of trees and barely get an itch from it.
I have some allergies to other stuff, like pollen in the springtime, and think that is a sign of why I barely have to be near it to get a rash from it. Some folks are more sensitive than others.
They say the oils are tough to get rid of. I have read that they can cling to clothing, through a wash cycle, and still affect your skin the next time you wear the clothes. Bath towels are notorious for spreading 2nd-hand Posion ivy. Your dogs fur can transmit it too.
The older I get the more I try to use a sensable approach to it.
If cutting firewood near poison ivy I try to do so when it's cooler out, winter being the best time. Cover your skin, and whatever you do, don't be perspiring and be around the leaves and vines. if you know you have been exposed, hit the TecNu fast, that's when it does the best magic and you can bypass a lot of the misery.
I once read where some scientists found some fossilized poison ivy leaves, millions of years old. They handled the fossils and got a poison ivy rash.
Go figure.
The last animal left on earth may be the cockroach, but the last plant will be the ivy/oak/sumac vine.