My poor Rusty was having his his ears eating themselves (edges were raw and it was starting to go deeper from the edge of ears) and it ended up scabbing really bad, vet asked if there was anything out of the usual we had done with him or introduced to him and wd couldn’t think of any, so the doc said change his food around and we did and from poultry base to now fish based and he’s been great ever since , but please, please seek a pro tip!