What Causes Rashes After Taking Prograf Post Liver Transplant?

I had liver transplant in1985. Been immunosuppresed since then. Taking 4 milligrams of Prograf .Developed a rash about 7 years ago. Tried tropicals, steroids etc. The only relief from the constant itching is injection of Kenelog every 4 to6 weeks. Question: could the skins immune system be breaking down and causing itching.no diagnosis or prognosis and seen every dermatologist in this area.