|Unfortunately (or fortunately depending on one's view), it is our more advanced immune system that is at work here. The reaction to urushiol oil is an overblown immune system reaction to what it considers a "foreign invader" -- in other words an allergic reaction. Dogs and cats are not affected by urushiol oil but as you noted can bring the oil into contact with the owner.
The poison ivy plant is itself beneficial in the wild providing food and shelter for birds and animals. I know that doesn't help lessen the itch but I'd like to think there is some redeeming value in this plant :-)