Dogs naturally lose old or damaged hair by shedding. Although shedding is a normal process for dogs, the amount and frequency of hair that is shed often depends upon their health and breed type. It can also depend on the season-many dogs develop thick coats in the winter that are then shed in the spring. Dogs who are always kept indoors, however, are prone to smaller fluctuations in coat thickness and tend to shed fairly evenly all year.
There are lots of reasons dogs may lose hair (also called alopecia), from infection to irritation caused by parasites. A few of the more common reasons include:
Allergies are a frequent trigger for hair loss in dogs. Like people, dogs can have an allergic reaction to foods, environmental triggers such as pollen, or to parasites like fleas or mites.
Flea bites are behind most dog allergies, however, and along with hair loss from licking and biting the irritated areas, signs of flea allergies include itching and redness. For a particularly allergic dog, it may take as little as one flea bite to start an allergic reaction that lingers for days.
While any dog can have allergies, some are more prone to them than others, including golden retrievers, dalmatians, boxers, Boston terriers, shih tzus, and Labrador retrievers. Treating your dog's allergies may include topical or internal medication, immunotherapy, a change in diet, and avoiding the allergen.
Hair loss in dogs may also be caused by hyperadrenocorticism, or Cushing's disease, a condition caused by the overproduction of the hormone cortisol. Less commonly, it is due to a tumor on one of the adrenal glands.
Medication is available to treat both forms of Cushing’s disease. However, surgery can be done to remove the tumor associated with the adrenal form of Cushing’s disease.
Cushing's disease is more common in dogs 6 years or older. Other signs of Cushing's disease include eating, drinking, and urinating more, as well as having a pot-bellied appearance.
Some dogs are more prone to baldness than others. Bald spots on the outer ear, chest, back, thighs, or lower neck may appear in whippets, Chihuahuas, dachshunds, and Italian greyhounds, usually after their first year.