Have you taken your dog to the vet for a healthy check up, as your dog get older things tend to change, you vet can check for the simple things first like external parasites such as fleas, ticks, lice, or mites. Your veterinarian will evaluate the health of the skin and coat of your dog. Special shampoos, additional grooming, supplements, or certain diagnostic tests may be recommended. Dry skin can be a problem for older dogs, and again, fatty acid supplements may be beneficial. Your vet may also check for allergies. I did a lot of research on your question an obtained my information from a site called
Pet Education.com. I hope that this was in some way helpful to you. (O: