
It can be very hard to treat and one application is not enough. You need to go back to your vet for a review and more treatment . It is contagous between dogs so the pup must be kept away from others dogs, no walks in the park ! and the house needs treatment as well. Surly the vet has some other form of treatment and did not just send you away without a proper course of action ? If so then I would be looking for a new vet quick sharp. It is actually lice that burrow under the skin.
Aileen
Added FYI
Cheyletiellosis is an itchy, scaling skin disease of dogs caused by infestation with Cheyletiella mites. It is often called "walking dandruff" because when you examine an infested dog, you may see that the "dandruff" is moving. The movement is actually caused by the mites moving around under the scales. Although the mites inhabit the entire body, the scaling and itching often seem worse over the back.
Cheyletiellosis is a contagious and a zoonotic disease, which means that it can be spread to and from other dogs, cats or humans. Dogs can acquire the infection from other pets or humans. The mite is transmitted by close contact with infested animals. Since the mite can live for a few days off the host, it is also possible to become infected through environmental contamination. Eggs are also shed into the environment, which is believed to also be an important cause of re-infestation.