PredniSONE and saviour

I had a kidney transplant a year and half ago, and had to take Prednisone as one of my post-transplant med's. I was on it for about 2 months and I went through a lot of the same side effects mentioned by other people, increased appetite and weight gain in odd places, sleeplessness, and acne. Then recently I had an allergic reaction to an antibiotic and was again prescribed prednisone for three weeks, but this time the acne is so bad it looks like a rash, and it's all over my back, chest, neck especially, and on my face. I can deal with it because I realize it's what I need to do, and I am grateful that there is a drug that can treat the symptoms from the allergy, but I am wondering how long it will take for the acne to clear up once I finish the 3 weeks? Does anyone know how long it takes when you've been on it for that amount of time? Any thoughts would be helpful. Thanks.
Megan