The worst case I got wasn't from climbing and cutting it, but from stump grinding. I got it all over my arms, face and in my sinuses.
After having my eyes swollen shut twice and a couple trips to the doctor for shots, I did a ton of research on the stuff.
TechNu . . . the best stuff there is to remove the oils.
You must wash within a few hours. It takes several hours to fully penetrate your skin.
The oozing is not contagious and won't give you (or anyone else) more poison ivy rash. Your skin is in different thickness and it can take longer for some areas to finally react, so it seems that you are developing a new rash from the oozing.
The oil can stay on clothes and tools for years.
I've read that you can't build up an immunity, and in fact with each dose you become more allergic.
If you get it real bad, just go to the doctor for a shot, some drugs and special cream, forget about all the over the counter stuff . . . it will be the best money you've ever spent.