Thanks so much, I have added the vinegar rinse and will be adding some garlic to his diet to see that will help any. It just breaks my heart that he has hardly any coat left and it just seems that no matter what I do it doesn't help.
An underactive immune system can lead to yeast overgrowth, because it can't control the balance. The other end of the spectrum is an overactive immune response where allergies are present. This can also lead to problems with yeast. When a traditional vet sees a dog with allergies (a sign of an overactive immune system) he or she will typically prescribe steroid therapy to shut off the immune response. It does improve symptoms but does not fix the underlying cause of the allergies. This is why your vet prescribed prednisone. When your dog's immune system is turned off with drugs, it can't do its job of regulating and balancing normal flora levels, so your pet ends up with yeast blooms. (which I think your dog has)
I know you said you changed his diet but the problem is still there so you have no choice but to revisit what he's eating. Diet is the foundation of health. The way you nourish your dog is either going to help his immune system manage yeast, or it's going to feed a potential or existing yeast overgrowth situation. Yeast needs sugar as a source of energy. Carbohydrates break down into sugar. Both doctors and veterinarians advise patients with yeast to get the sugars out of their diets. You'll need to carefully read his pet food and treat labels and avoid any product containing honey, high fructose corn syrup, and even white potatoes and sweet potatoes.
I recommend you go entirely sugar-free. Eliminate potatoes, corn, wheat, rice – all the carbohydrates need to go away in a sugar-free diet. This is really an important step. I wish I could tell you yeast is easy to treat and avoid without addressing diet, but it isn't. Your pet needs to eat a diet that helps keep his normal flora levels healthy and balanced. I would recommend a Raw diet. If you want to learn more about it PM me.
The second thing I recommend is adding some natural anti-fungal foods to his diet, like a small amount of garlic or oregano. These foods are both anti-fungal and anti-yeast and can be beneficial in helping reduce the yeast level in your dog's body. Also, continue using the shampoo as often as needed. Hope this helps...Good luck