There are many variations that divide dog breeds. One of which is the single coated and double coated breeds. As the name suggests, double coated dogs have two layers of hair. ‘Guard’ hairs are the longer top coat which repel dirt and moisture from penetrating the skin too much, while the undercoat of shorter hairs (usually of a dense, fluffy texture) serve to protect the dog from the planet’s extreme climates. These double coats shield the dog from the scorching rays of the sun (especially those with white hair), and provides insulation from freezing below-zero temperatures. These dog breeds also shed twice in a year to keep skin and fur healthy, allowing damaged hair and dead skin cells to drop off, replaced with newer, rejuvenated ones.