Dog hair grows in cycles. Each follicle has a period of rapid growth (the anagen phase), followed by slower growth and then a resting phase (the catagen phase). During the resting phase, mature hair remains in the follicles and eventually detaches at the base. When the dog sheds her coat (the telogen phase), a young hair pushes out the old hair and the cycle begins anew. The average dog takes about four months to grow a coat, but there are individual and breed variations. The Afghan Hound, for example, grows her coat in about 18 months.
There are “hairless” dog breeds, such as the Chinese Crested (which has hair on the head, tail, and legs) and the Xoloitzcuintal (which is normally hairless except for a single tuft on the head and some long hairs on the tail). Both of these breeds have coated versions as well. The hairless condition in these dogs is due to a genetic mutation, not a health problem.
Most dogs shed or “blow” their coat at least once a year. Dams often blow their coat six to eight weeks after delivering puppies. Major shedding may follow a bitch’s heat cycle as well, due to the hormonal swings.
Many people assume that temperature changes govern when a dog sheds her coat. In fact, the seasonal length of daylight exerts the major influence. Longer periods of daylight in spring activate a shedding process that lasts four to six weeks. In fall, as the daylight hours grow shorter, many dogs may again shed their coat. Sensitivity to ambient light is most pronounced in dogs who live outdoors. Dogs who live primarily indoors are exposed to artificial light and a rather fixed photo period. These dogs may shed and grow new coats all
Some breeds, such as Poodles, Bedlington Terriers, and Kerry Blue Terriers, have what is called a nonshedding curly coat. These breeds do not shed loose hair into your house. Instead, their loose hair tends to collect into mats that remain on the body. Dogs with corded coats, such as the Puli and Komondor, have similar coats, but their hair works itself into cords.
Some dogs have a double coat comprised of long, coarse outer guard hairs and a soft, fine, wooly undercoat. When a dog with a double coat begins to shed, the appearance of the coat can be quite alarming. The undercoat is shed in a mosaic or patchy fashion, giving the dog a moth-eaten appearance that may suggest a skin disease.
When shedding begins, remove as much of the irritating dead hair as possible by daily brushing. In breeds with a thick double coat, a bath will loosen the dead hair and make it easier to remove. Always brush out a dog before bathing to help prevent the formation of mats.