Dogs that moult twice a year shed their hair in the spring and fall to coat the most suitable coat for the season. Some dogs like Nordic dogs have very slow shoots. The slightest mowing will take time to regrow. Curly dogs such as poodles shed so inconspicuously and hair growth so long that it seems like they never shed hair.

Under stress, dogs can also lose a large amount of hair, in a diffuse way, all at once.

In these cases we do not speak of alopecia and it is completely normal for a dog to lose his hair.

A dog that is losing its hair can be affected by a variety of and sometimes concomitant diseases. Many diseases by creating inflammation of the skin and itching promote the development of bacteria and therefore bacterial superinfection.

Parasitic diseases that cause inflammation and itching (dog scratching) can cause hair loss. Mention may be made of dog mange or dog fleas as an example of a parasitic infestation creating alopecia. A dog who is losing his hair can also be infected with an internal parasite, leishmaniasis, which causes general lesions (depression, weight loss) and skin lesions.

Fungal infections

Diseases linked to the presence of a fungus such as ringworm create very typical alopecia: they are circular, there are broken hairs and generally do not itch. Please note that ringworm is a zoonosis and creates circular lesions on the skin of people living with the affected dog. People or other pets such as guinea pigs can pass ringworm to dogs.

Bacterial infections

Bacterial infections also called pyoderma cause very itchy, hairy, red and sometimes oozing lesions. They can be associated with parasitic or fungal infections.

Dog allergy-related diseases such as atopic dermatitis or food allergies cause significant inflammation of the skin and ears (we speak of dog ear infection). Secondary may develop pyoderma or fungal infection.

Genetic diseases

Certain genetic or congenital diseases such as alopecia of the dresses diluted or alopecia X.

Endocrine diseases

Endocrine diseases such as hypothyroidism in dogs (thyroid hormones are not secreted in sufficient quantities) cause typical “rat tail” and flank alopecia.

There are other alopecias that are not related to diseases such as the dog losing his hair where he wears a collar or an elastic that is too tight, at the site of an injection made by the veterinarian and finally alopecia of the tail glands of whole male dogs.

Consult your veterinarian. In the presence of unexplained hair loss in the dog, the veterinarian will take a complete history to know the dog’s history (seasonal or cyclical aspect of alopecia, itching, frequency of anti-parasitic treatments, injections, trips, etc.) . He will find out if the dog has other more general symptoms. Polydipsia (dog who drinks a lot of water) and depression, for example, can make you think of endocrine disease or leishmaniasis.

He will then do a complete examination of the animal’s body, looking for parasites such as fleas. The location of hair loss can direct it to a particular disease. He will also note their appearance, color, the presence of oozing and other skin lesions such as pimples or scales.

The veterinarian has many additional examinations to determine the origin of the dermatological lesions:

• Trichogramma: it shaves the dog and looks at the hair under the microscope
• Skin scraping: with a blunt scalpel blade he scrapes the skin until it bleeds a little. This deep scraping makes it possible to highlight the parasites installed deep in the dog’s skin.
• The scotch-test or the tracing paper: with a scotch tape or a glass slide, he will take cells by pressing them on the skin. After a quick staining, he will observe them under a microscope looking for immunity cells, bacteria or yeasts. On the tape he can also observe the microscopic appearance of dead hairs
• Wood’s lamp: with this UV lamp that he passes over the lesions, he looks for a ringworm, the nasty hairs become fluorescent under this lamp. Sometimes this test is negative despite the presence of a ringworm, if the veterinarian has any doubts he can make a mycoculture of the hairs on a special culture gel and check in at least one week if fungi are developing.
• Blood test: to check for organs for damage, check for endocrine disease or leishmaniasis infection (a general parasitic disease that results in skin lesions)

The treatments obviously depend on the disease found. Few treatments are effective on alopecia of genetic or congenital origin.

An external anti-parasitic treatment is applied even if the results do not show the presence of a parasite. Some parasites like dog mange cause itchy hair loss and can be difficult to find even for veterinary dermatologists.

Certain dietary supplements like omega 3s or vitamins can affect certain types of dogs who are losing their hair (especially when they are deficient in the diet or have dog diarrhea).