Jake is loosing fur and has skin issues. He is on thyroid medication and checks out fine. We give him brewers yeast as well as a special oil additive to his food. We shampoo with oatmeal and aloe. We do not want to go thru a battery of testing since he is 15. No changes otherwise. This has been going on about 8 months and he has had two rounds of antibiotics as well as a shot which seems to have lasted the longest.  Any help and guidance would be greatly appreciated.