This is not one of those times. I would not wish this on my worst enemy much less one of my characters. On the rare occasion I come across an author using this as a plot point, I'm going to think "Low blow, author. Low blow."
What event am I talking about?
Coming into contact with poison oak/ivy/sumac and not realizing it in time to wash it off.
I now have a line of raised blisters on my arm and a rash around them that itches worse than anything I have ever encountered. I have had to trim my fingernails back because when I wake up in the morning/middle of the night it's to discover myself scratching frantically at my arm in my sleep. I have every anti-itch remedy I can fine in this house, and it still doesn't completely stop the itch. The blisters are nasty looking and if they pop, they weep and crust over. It's disgusting, but more than anything, it's itchy.
I'm not even 100% sure what I came into contact with. The entire back slope is a mess of vines and weeds. I'm pretty sure it's not poison ivy: I can instantly recognize that. Poison sumac is more shrub like than most of what we have back there. My guess is poison oak, which would be hard to distinguish from all the oak saplings and trees.
And of course, I discovered that I didn't immediately break out so I could then go wash it off. Oh no. My skin started itching and blistering almost 10 hours after I came in contact when the urushiol had had time to be absorbed. Hence the nice blisters. From what I've read on-line, the rash can continue to erupt up to 7 days after it first appears. This started Thursday. ;_;
Then again, maybe I can use this. Only instead of poison ivy, maybe I can give my characters silver poisoning or something. Because I guarantee after this, I'm not even going to want to hear the word poison ivy/oak/sumac for a long, long time.