Coloured scanning electron micrograph (SEM) Dog hair (shih tzu) with damaged cuticle. Dogs have two types of hair in their coats. The first type is short fluffy hairs called secondary hairs. Other names for secondary hairs include underfur and undercoat. The second type of hair is the longer and stiffer outer hairs called primary hairs. Primary hairs are also referred to as guard hairs, outer hairs, or outer coat. Dogs also have a third type of hair: the whisker. Whiskers are called tactile hairs because they help the dog sense his surroundings. Each hair grows from a simple opening within the skin called a hair follicle. Even though all dogs have the shorter secondary hairs and longer primary hairs, the ratio differs by age and breed. Newborn puppies lack primary hairs. Each hair grows from a simple opening within the skin called a hair follicle. Magnification: x240 when shortest axis printed at 25 millimetres.