Other less common possibilities for flaky skin in dogs include ichthyosis, sebaceous adenitis or primary seborrhoea sicca — all of which are primary keratinisation defects of the skin. (petsmagazine.com.sg)
Fungal infection, bacterial infection, allergies, seborrhoea etc... would all be possible causes; your Veterinarian would be able to take a skin scraping to see if there are any mites. (wagwalking.com)
Some animals are battling seborrhoea (excessive oil production of the skin) and thus are naturally predisposed to the yeast proliferation. (lowchensaustralia.com)