I'm not a doctor so am unable to evaluate about the rash. What I will tell you though is through my reading I learned that too short a course of oral steroids (i.e. prednisone) the rash can and many times does come back with an even stronger vengence. First let me give you some reading material here to back this up:

• Dr. Hempel's writing on the rash and treatment
• FDA document on poison rash, treatment, and the plants. Note: Dr. Williford recommends at least a 14 day if not 3 week run of an oral steroid otherwise you may end up with a rebound rash.

Since you are on your 3rd round of prednisone in 4 weeks, your prescriptions for a course of steroids are not as long as recommended by the above mentioned physicians. Could it be that you are dealing with a rebound rash?

Read the references above and if you need more material, let me know as I've come across many more similar references. You should consider discussing this information with your doctor or perhaps get a second opinion from another doctor. The normal course for a poison ivy rash is about 2 weeks. Systemic reactions (such as inhaling smoke from burning pi plants) can take up to 5 weeks to go away - or so I've read. I've always been blessed with the normal course of PI - 2-3 weeks and then its gone.

Goood luck!