Depending upon how dangerous the invader is, your body will change its response accordingly. Of course your body will sometimes go overboard and you will develop a severe allergic reaction. Such a reaction, whether to poison ivy or something else, can be life threatening. So you see, the key to poison ivy is this oil. You must keep it off your skin in order to protect yourself.
Clothing is always a good defense.
But be careful urushiol can remain active on clothing or pet fur for days. Poison ivy is truly a tough weed. You can't burn it up, because the smoke will carry the urushiol through the air. You can't pile it up, because the dead stems can still infect you. Probably your best bet is to just avoid it.