I was never on IVSM, but a course of prednisone gave me horrible
acne all over my face and onto my neck and
back. It did clear up just fine, I think in about 2 weeks most visible traces were gone.
It was embarrassing, I went through this while at a conference and had to make a presentation at peak pepperoni face level.
I didn't do anything to treat it, I just waited it out. I stuck with my usual: I don't wear any foundation, and use mild soap to wash my face.