It seems to work on furry animals with skin problems, usually a nutritional problem.
I feed raw diet almost exclusively, when the dry is gone, its never coming back.
I use chicken backs (raw), turkey necks, chicken necks, about once a week organ meat, a few dollars of fresh greens and veggies ran through a processor for a few minutes to liquify them, I freeze whats not being fed that night and feed 1-2 tablespoons a night. If interested in the raw diet which gets rid of all nutritional problems in dogs read Dr Ian Billinghursts book "Give your dog a bone".
I also use a complete ground raw diet added to that which has kelp, and I add salmon oil (a teaspoon a day) or feed a few raw fish a week.
I hope the brewers yeast helps. Could it be a problem with the heat and humidity, fungus, Im not sure.