Breed predispositions for the allergic causes, such as dogs are chewing their nails and causing them to break, include: Golden retriever, Labrador retrievers, Westies and other terriers, German Shepherd, Bichon Frise, Maltese, and the list goes on. It can be hard to get to the root of the cause. Your veterinarian likely will recommend starting with some basic diagnostics to rule out infectious causes first.