What Does An Itchy Rash On The Shoulder Blade Indicate?

Hello, thank you for trying to help me. I m an 81 yr old woman who has been bothered for several years, by an extremely itchy patch on my left shoulder blade which never has left. Often, another itch will occur at the same time (not as severe), on the right shoulder blade. I ve been applying Betaderm cream to these areas to try to get relief. This has helped relieve the itch for a couple days, then it returns as intensely as before use of the cream. This past 3 weeks much of my body has now become extremely itchy, usually my scratching intensifies the problem. I noticed a discoloured area on the under-side of the left breast, in the center was a very small open spot which was a bit wet, which I assumed was pus, or infection. This area has now healed, no more matter coming from it, and also the discoloured area has reduced in size from one large, oblong shape into 4 much smaller little circles. The doctor prescribed an oral Sulpha-type drug, not realizing that Sulpha was on my long list of drug allergies......I did not use it. He now has prescribed Cephalexin, however I m nervous about taking it, as I have had so very many bad allergic reactions to Antibiotics in past early years. I have a prescription for Prednisone (5 mg.), which I had not used, so I took one tablet at suppertime last night, in hope that I would be able to get some sleep last night. It did help tone down the itch quite a bit (not entirely) but at least I got considerable relief. So, again at suppertime tonight, I took another, again hoping for sleep. This is my dilemma, do you think you can help me, please? Thank you so much. SIncerely, Coralie Bond