There are 2 very important medical aspects that need to be addressed: Firstly the nutritional aspect – she needs to be put on a good quality food that is fully balanced and is recommended by a veterinary professional. What you put in is what you get out and the skin is the first organ of the body to suffer with poor nutrition.
Adding brewers yeast is not going to help and also adds to medical imbalances and will likely lead to some other complications long term including kidney problems. Most people that do not have their pets on professionally recommended food by your veterinarian either have not been told by their veterinarian which food is best for their dog ( in which case I suggest you switch to a more proactive veterinarian) or the client either doesn’t follow the recommendation for a variety of their own reasons that they feel is justified.
Secondly, your pet may have developed a hormonal disease with age, most commonly a thyroid deficiency which can easily be diagnosed with a blood test and easily treated.
This is obviously only touching the surface of what could be happening but these are the 2 conditions most commonly seen in my practice causing the symptoms you mention.
I hope the solution is simple either way. Please be aware that skin conditions take a month or 2 two before you see things starting to improve, so be patient.
Martin Slome DVM
Centre Street Animal Hospital
7700 Bathurst Street Units 40-42
Tel. (905) 771-9855