Doctor has me on prednisone too. Got a shot on the 4th day after exposure and started the oral drugs on the 5th day. My prescription is much different from yours though. 40mg for 4 days, 30mg for 4 days, 20mg for 4 days, and 10 for 4 days. I'm on day 3 of the 40mg right now. Doing ok with no real side effects so far. Maybe your dosage was too high??? Hmmmmm.
I agree with the calamine lotion. I was using Caladryl brand but it is incredibly drying to my sensative skin, but then again, it's supposed to dry it. I'm using Caladryl now on only the big blisters; Gold Bond Medicated Lotion on the dry but healing spots, and like you, hydrocortisone cream on the remaining "hot spots."
Everyone reacts to the PI and the treatments a little differently. I'm sorry you had such a rough time.