I had Pupps with both pregnancy. It is a total PITA!!! You can have one round of steroids, which helps when it's really bad, but that's it one round, after that it's all about anti-itch creams & cold showers, which sucks during a winter pregnancy!!
They're not exactly sure what causes it, but the leading theories are that a) you're allergic to your own pregnancy hormones or b) something the man contributes to the baby's genetic makeup. Either way it's itchy & uncomfortable. I found that over-the-counter allergy pills (a generic 24-hour one) helped a ton, as did Caladryl lotion, they have a clear one that helped a lot.
Funny that you're getting it with your second pregnancy, not the first. Usually it's the first, I was told I wouldn't get it with my second one, HA! And I learned that it's more common with heavier moms, dunno if that applies, but this is supposed to be pretty uncommon, lucky us!
Good luck & congrats on the new baby!
D.