Could be a lot of things. It may be that your dog needs a fatty acid supplement. If he stratches alot it could be fleas, lice, or mites. Also maybe the shampoo or bathing too frequently. Go to this site and do a search for dandruff. If you do decide to switch foods do the change over a period 5-10 days to avoid upset stomach and give it time, at least a month or two to before evaluating any changes in the coat.

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