The dog's coat has the effect of protecting the dog from external stimuli and helping to maintain normal body temperature. The structure of the coat consists of two parts, the outer layer and the secondary hair. The outer layer or the rough hair is mainly responsible for protecting the skin. It is characterized by hard, thick and long; the secondary hair is short and velvety. The lower hair (also known as the bottom hair) is mainly responsible for adjusting the temperature and the texture is soft. Thick undercoats are important for dogs in cold regions, but not all dogs have undercoats. The coat also has a beautiful and protective function and reflects the overall health of the dog. The coat can be either solid or motley. The healthy growth of canine hair is highly dependent on sweat glands and sebaceous glands.