I have some way in the back yard. I know to avoid it, but once in a while I'll get some on my leg or arm. It's an oil that gets on your shoe, then you touch your shoe and your hand moves it to your arm.

Scratch it and it will spread. You need to leave it alone, but you can't stop scratching it. I have been successful spraying my arm with some anti fungal athlete's foot spray then coating the area with Aloe Vera gell. Between the two of them the itching is less and the Aloe Vera protects my skin from spreading if I do scratch and break the blisters.

Some years ago three kids were smoking pot next to the poison ivy patch. When they say me the threw it in the deep poison ivy patch. When I walked away two of them went into retrieve it. What was I going to do? They would not have listened to me anyway.