i, too, have heard you can desensitize yourself by eating small amounts of the very young, tender leaves over time. never had the bells to try it.
i've also found that whenever you have a large, dispersed patch of poison ivy that comes back yearly - look up. you'll probably see the parent plant climbing a tall tree and that plant is both putting out runners AND getting enough sun to make and disperse seeds. no wonder it's so hard to get rid of!
i've also read in serious poison ivy pamphlets and literature that the resin can not only stick around for weeks but for years on tools, gloves, clothing, etc. regular detergent and water will remove it from all surfaces except skin to which it bonds and must be removed using a special blend of surfactants such as go-jo or zanfel which have the correct chained fatty acid to grab the oil on one end and a water molecule on the other.
as we all know, regular soaps will not do the job once it's bonded to the skin. these documents also indicate you have about 4 hours to wash off the oil from your skin before the bonding process begins to make regular soap and water ineffective and you have to go to the specialized soaps.
sorry to hear about the fellow who passed away due to this. i've felt pretty downright miserable from it until i started to learn about it. he probably had what is termed a "systemic" case. if you get enough oil on your skin, it can get into your lymph system and travel to other parts of the body where your own immune system does you in by trying to attack the oil. this occurs when large portions of the dermis are covered or you breath it in in aerosol or smoke form and it gets direct access to lymph and blood system.
i think i had a partial systemic case once when i cut some spring vines (unknowingly) and the sap dripped directly onto my legs. you could actually see the streaks in blister form where the vines had rubbed across my bare legs and the sap had left a trail. not fun.... to this day, i get itchy when i get close to the stuff as if my body has become a highly tuned detector of the plant just from it's airborne chemicals. i know that sounds crazy, but it's a real feeling i get sometimes and when i look around i usually find a good amount of the plant.
amp