Rash and nephropathy

I have experienced hives and nonspecific eosinophylia with mild renal insufficiency. I have eliminated most medications which might cause this but still experince very troublesome rash with itching. I tried all the customery treatments.  I am unable to use steroids, except tyopical because of diabetes.  What are your thoughts in regards to skin testing and medications to relieve itching.  I am taking claritin during the day and Zyrtec at night