m not sure but I can tell you an issue that may be similar which
my dog faced about a month ago.
My dog is a 2 year old doberman/black lab mix. We took him to the vet because he was itching, had light dandruff. The vet said that he was having a allergic reaction to something (I'm in Philadelphia and about a month ago, spring was here and he was outside more). She said it could be anything outside, or in the air. She told us to change his food to one that had fish oil in it.
So far, so good.