I am hyper allergic to the stuff.
Ivyblock, Ivycleanse and washing up is about all you can do. If the oil gets on you skin or under the block and stays there you are still screwed.
I hunt and fish and ramble around a lot in some deep woods and creeks and where I go its loaded with poison ivy (crawling on trees etc) poison sumac, and poison oak.
There are certain places it grows. It likes a certain type of light and soil so learn that. For some reason it does not like to grow around Pine trees.
The only solution is to stay away from it and shower in a harsh oil cutting soap, like dishwashing soap, octagon or a lye based soap every night and to wash you cloths.
I have found that I can basically touch it, get in it or whatever, and as long as I take a good shower and wash my cloths I will usually be okay.
Not going to happen on a hiking trip though so the best thing is to learn what it looks like and stay away. I now can spot it from 50 yards, but it is sometimes easy to miss.
I also found that if you think you might have gotten it, clean up and sleep in a t shirt so you dont spread it to your chest, but if you get it on the inside of your sleeping bag your screwed anyway until that is washed and with a down bag you definately do not want to use an oil cutting soap.
Probably a good reason to use a silk or other fast drying liner.
I used to get it really bad when I was a kid, and I went through a series of treatments with some sort of a green gel goo injected with a huge freekin needleover a years period maybe every 2 months.
I did not get the itch for 3-4 years after.
I recently inquired about it, to a dermatologist and nobody had ever heard of it.
All I can say is you have to wash your hands and everything else a lot with strong soap and for gods sake, wash your hands before you pee, not after. I did that once too. Disasterous results.
Looking back lately at the times I have gotten it, I would say 90% of the time it came from my boots or putting my hand on a tree with a vine with a poison ivy vine with no leaves, then touching my face or some other part. When hunting deer I have gotten it numous time from loading a deer into a truck, IE grabbing the legs. I have probably gotten it 5-10 times like that.
If you are in poison oak/ivy plant country, treat your shoes, bottom of your pants and hands as if they are contaminated all the time you will do okay.
Take off your shoes, if you think your pants have been in contact take them off, and anything else that has been in contact, clean your hands and face and anything else contaminated and put on ivy block.
IE dont touch your face etc before you wash your hands, and scrub everything
They also make a ivy cleanse towelette you can wipe down with.
Its a real PIA but you have to change the way you do everyday things, but it seems to work for me.
Gloves seems to help too. In the summer I wear a pair of super thin gloves when I am in the woods.
I have managed to avoid poison oak while hiking all these years, but I am very poison oak paranoid, because I know it would be a major disaster for me.