
Hi,
I went through something very similar with my beautiful GSD. She started off with tummy rashes as a pup which eventually was diagnosed as Demodex. She was shaved completely and treated with baths ( Aludex etc ) but it did not clear up. As she got older her immune system stopped working and she became allergic to most things including dust, grass and sometimes me. Diet made no difference at all.
She went back and forth to Bristol Vet. College where they dug around trying to find the demodex mite, but it was so deep in her body by then they could not be found and damage was being done to her internal organs. She lived on antibiotics as within 2 days of leaving them off she was covered in weeping sores.
She had a wonderful character and put up with it all. She was insured but I was still adding thousands each year to top this up, she cost around £8000 per year ( this is 10 years ago )
Eventually the vet told me that there was nothing else they could do and I felt that she had put up with so much it would be kinder to let her go. She was by this time 6 years old. On hind sight I wish I had not continued for so long as she didn't deserve to suffer for so long, it was just the hope that she could be cured. They even did skin scrapings which they turned into a vaccine and injected back into her to try to help her fight this.
I sincerely hope that this is not what you dear dog is suffering from, but if it is and your specialist feels that there is nothing more he can do, please consider what is best for her as this is my one big regret that maybe I kept her for so long because I couldn't bear to let go.
My thoughts and prayers are with you in the hope that he doesn't have this awful condition and that he can get better.( please give him a hug from me )