I had PUPPs with my son. Nothing dangerous...just really, really, itchy and annoying!
It started a bit about a week before I gave birth. Wasn't too horrible at all. Didn't think much of it.
After I gave birth, it became HORRIBLE! Worst thing I ever had. I wanted to scratch my skin off. I would go through whole tubes of steroid cream.
I had a c section so couldn't take baths for awhile. When I could, I would soak in some sort of bath (oatmeal maybe...can't remember).
It lasted about 3 weeks.
Good news is that I had no time to feel any pain from my csection bc my rash drove me nuts instead!
Nothing at all with my second son.
Good luck!