This is often a symptom of an allergic reaction to food. Have you recently switched dog food brands? Has your dog been scratching or chewing on his skin?
Keratin Feathers scales appear on the bottom of dogs paws. Groomers usually would notice the problem and provide you with over the counter cream to help with this condition.
Could be due to chemicals the dog might walk on or a number of conditions including yeast infections, diet lacking zinc, or an autoimmune disorder. Contact vet if it persists.