How long does poison ivy last if taking prednisone?

I actually came in contact with the poison ivy or oak last wednesday, but the rash didn't show up till friday. This is my first time with poison ivy. I went to the doctor and he gave me a z-pack because it got infected, but he also gave me prednisone. Will the prednisone speed up the healing process? How long will it take? I've got it on my face, my lower back/ area (not fun). I just want to get better by my birthday on the 21st. Any ideas on whether I will be or not?