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Thanks for asking your question on Just Answer. Seborrheic dermatitis is a common skin disorder in some breeds. But, it is important not to go by "look alone" in making the diagnosis. It is possible that your dog has a secondary bacterial or fungal infection, attributing to the change in skin color as well. Until all underlying infections are treated, this won't go away. Retin A can help, but there are other treatments available as well.
Did your vet do a biopsy to get the diagnosis? Did they do a fungal culture? These are important steps.
If your dog is itchy, this adds other possibilities into the mix like allergies.
Awaiting your reply to the questions I've posed so I can assist you further....
I would absolutely insist on a biopsy and fungal culture. Your vet should also do what is called an impression smear (he takes a slide and presses it against the lesions) and then stains it to look for bacterial infection. You can't really treat something unless you know what it is. It sounds like your dog has "yeast issues" if she has chronic ear infections. Response FP is fine, but it's not a truly hypoallergenic diet.
You can also ask your vet to refer you to a veterinary dermatologist. That would be the best course of action. It isn't that expensive and you are getting the benefit of a board certified practitioner who only does dermatology. They often have treatment options that general practitioners don't. The cost of a consult is less than 2 followups at your vet.
I hope that this is helpful. Please let me know if you need more information. If you are interested in addressing this from a homeopathic perspective (natural medicine) vs. allopathic (western), please let me know and we can discuss a future "telemedicine" consult.