It's other varieties of the same species that are that potent - possibly Javanese (I'd have to look it up).
Ours aren't quite that strong (unless you have a severe allergic reaction maybe) but they do cause epic bouts of swearing sometimes...
Seeds and plants were sent from north America to europe (notably France and the UK) by botanists and made available to plant collectors and medical and other researchers, definitely cultivated at Kew gardens and recorded in multiple private locations.
There are recorded instances of it being successful in treatment of some skin problems (the body fighting the urushiol reaction promotes other healing), but these are from the Victorian era, so a grain or two of salt may be required.
You think that stuff grows rampant, try some Japanese knotweed - that'll grow four inches per day in summer and easily survive being composted. If you shred it, every fibre will grow a new plant. It's policy in most councils that they can issue a fine if it's disposed of through normal "green waste" channels unless burnt first and there are companies dedicated to specialist removal and soil treatment.
That was introduced to the UK in the 1800s as a quick growing and hardy ornamental garden plant, especially suited to amateur gardeners...
