Vacuum cleaners are permanent fixtures in the corner to make it easier to suck up the hair several times a day. All over the country, pet owners are grooming their retrievers and setters and spaniels and shepherds and northern breeds, loosening great avalanches of fur. An accumulation of hair through the month or so of shedding season looks like enough to knit a whole other dog or at least to stuff a set of throw pillows for the sofa. Then, just when owners think they can't stand another minute of crumbling canine coiffures, the shedding stops, the new coat gradually fills in, and Mom can put the vacuum cleaner back into the closet. Although admittedly a source of frustration during shedding season, dog hair is a marvelous body structure efficient at insulation, skin protection, and sensory perception.
All mammals have some sort of hair covering some, much, or virtually all of their bodies.
Hair is made of the protein keratin and dead epidermal or skin cells and it grows from follicles in the dermis or inner layer of the skin. Some hairs are densely packed into stiff, fibrous outgrowths that, depending on species and location on the body, become horns, fingernails, and toenails. Human follicles each give rise to a single hair, but animals that depend on fur coats for temperature regulation often have several or many hairs per follicle. The diameter of individual hairs decreases as the number of hairs per follicle increases. Each follicle has an oil or sebaceous gland to keep skin and hair smooth and elastic.