What Causes Recurring Left-sided Fluid Oozing Red Rashes On The Body?

I have symptoms on the left side only. Originally presented as what looked like little red bumps. Then spread to what looked like a rash on my left forearm, thigh, ankle and across the left flank of the abdomen. Have been treated with prednisone for 2.5 weeks started at 60mg daily/week, then 40mg daily/week, now have 4 days left at 20mg daily and the redness and itchiness is back. All has cleared up except the thigh redness which was the worst. The skin broke down to the degree of a healing blister. The redness is oozing serous fluid that is NOT impetigo, swab came back negative for infectious process. Blood cultures are negative, antibody tests are negative. After 2.5 weeks of prednisone the redness has returned as well as the itchiness, localized to the left side of the body only, and looks as if it is ready to start oozing serous fluid again, never crusting over. No known drug/food allergies. No change in laundry detergent or life style changes. Have had animals for the last 15 years without issue, no exposure to poison oak. Work in a hospital since 2006 in the Cath Lab with no issues to this degree, have been sent out on medical leave with no answer. What could this possibly be that it is returning while on prednisone?