Most breeds have normal shedding cycles, although some breeds, like the poodle, have continuous hair growth. However, if your dog's coat is becoming thin or has bald spots, there may be a problem. There can be many causes for hair loss.

Itching

If your dog is scratching, your veterinarian may check for flea allergies or mites, including scabies and demodectic mange mites. According to Mike Richards, DVM, in Vetinfo,com, triangle-shaped patches with the wider part toward the tail is often from a flea or mosquito reaction. Loss of hair on ears and head often indicate mites. Bald spots may also be ringworm.

Cushing

Cushing disease, hyperadrenocorticism, is a common hormonal disorder. The adrenal glands produce too much cortisol, which the Dogs Guide says will result in evenly distributed hair loss and the skin turning darker.

Hypothyroidism

If the thyroid does not produce enough hormones, your dog's coat may thin. Some dogs experience heavy loss on the tail region.

Baldness

According to the Marvista Veterinary Hospital website, when no reason for the hair loss can be determined, it is called "Alopecia X." It is also called other names, including hair cycle arrest, black skin disease and follicular dysplasia of the Siberian Husky.

Considerations

Both poor nutrition and aging may cause hair loss. Your veterinarian may need to do skin scrapings and blood work to determine the cause.

Source:

Vetinfo4dogs.com Hair Loss Problems in Dogs

Cushing's Disease in Dogs Guide: Symptoms Of Cushing's Disease In Dogs

MarvistaVet.com: Alopecia X

More Information:

Dog Colour Genetics Primer & Free Canine Genetics Software

Groomer's Reference.com: Dog Grooming Information

Vetinfo4dogs.com The Major Canine Allergies: Inhalants, Foods and Pests