Adult Fifths Disease - adverse reaction to Prednisone?

Two weeks ago, I had a full body rash (everywhere BUT my face) that lasted 2 days, followed by severe joint pain and inflammation (practically every joint in my body ached).  After 2 days of aching, my doctor prescribed a 6-day pack of Prednisone.  Note that my doctor had never seen a patient for adult Fifths Disease - he merely prescribed the steroids to attack the joint inflammation.  Also, the blood test for parvovirus was positive.  I was happy w/ the results of the steroids until 2 days ago.  I stopped the Prednisone on 3/10/10 and for the last 2 days, my face has been flushed - BRIGHT red, hot and itchy (so, 4-5 days after stopping the steroids).  

I saw a different doctor today (mine was booked up) who attributed the facial rash to Fifths Disease (even though I had not previously had a race on my face) rather than an allergic reaction to Prednisone.  From what I have been reading online, though, perhaps it is the virus - intensified by the Prednisone.  This doctor told me to wait it out.  My questions are 1) How long does Prednisone stay in the system?  2) Is it likely that I would see a reaction to the steroids 4-5 days later?  3) Does Fifths Disease typically react adversely to Prednisone? 4) what should I do?

Thank you!