Muzzle Rubbing

Question
I have a 4 yr. old Golden Retriever. She rubs her muzzle on the floor in front of her food bowl. We have changed her food (Beef, Chicken, Lamb etc...) And that made no difference. We have given her Royal Cannin, Organic dry food, She gets canned every morning. I have tried the Raw Diet. Nothing has made a difference. She will rub until bleeding if we are not there to stop her.
Why????

Answer
I can't really tell you why without visiting and observing your setup and the behavior, but I can give you some ideas to help solve the problem.
You could try moving her dishes to a new location or elevating them so she doesn't have to bend down to eat. It is probably a good idea to only put her food down for 15 minutes at a time and watch her while she eats and then remove the dishes so she doesn't have access to them between meals. You may even wish to restrict her access to the feeding area between meals. I do not think this issue is related to the type of food she is being given. But again, I would have to observe to know for sure.