Here's a Forest Ranger technique:
Do the work around Poison Ivy fast. Git'er done, in and out.
(Do NOT burn the stuff! Smoke'll make everyone sick for yards (miles?) around! It carries the poisonous oils far and wide; inhale it and you are in some deeep yogurt.)
Now RUN to the nearest shower. Ditch your clothes and heave'em into a plastic trash bag for throwing away.
Take a cold, COLD shower - cold as you can stand. Cold water closes off the pores and at the same time it makes the poison ivy oil really thick and therefore less likely to spread.
Now grab... one of those dishwashing soaps that CUTS THROUGH THE GREASE. Sound familiar? Now what is oil but a form of... grease. Right?
Soap-suds your tender l'il bod all over with this grease-cutting wonder soap.
Rinse. Then repeat as often as possible - until you turn blue from all that cold water, maybe?
Why does this work?
The trick is to do this ASAP after you've been exposed:
* use C-O-L-D water; and
* use that dishwashing liquid (not dishwasher - the soap for hand-washing those grimy greasy dishes) to cut the viscous poison ivy oils and send them harmlessly down the drain.
And do be sure to either scrub those clothes really well or (wisest) trash them as you take them off.
Hope this saves some of you from the torments of a case of poison ivy!