Overview of Canine Hair Loss
Alopecia is the complete or partial lack of hair in any area of the skin where hair would normally be found. In dogs, it may be caused by self-trauma by scratching or chewing, hair follicle diseases that cause the hair to fall out, or the failure of hair to grow after normal loss.
Severe hair loss makes your dog more susceptible to the elements. In addition, some of the diseases that can cause alopecia may also have harmful effects on other organ systems of your dog.
What to Watch For
Abnormal appearance of the skin
Diagnosis of Alopecia in Dogs
As with any disease, a complete history is very important. Be prepared to answer questions such as:
How long has your pet had alopecia?
How severe is the hair loss?
Has any hair regrown?
Does your dog itch?
Have you used any medications and if so, were they helpful?
Following a complete history, your veterinarian will perform a thorough physical examination of the skin paying special attention to the pattern of alopecia, the appearance of the skin and how easy the hair comes out. A flea comb may be used to look for fleas, flea dirt or other parasites.
Diagnostic tests that may be needed to determine the cause of the alopecia include:
A trichogram. A microscopic exam of the hair may be done to determine if the hair is being pulled out or simply falling out.
Skin scrapings. Your veterinarian scrapes a blade against the skin to remove some surface cells to look for mange mites and other parasites.
A fungal culture. This determines whether ringworm is present.
A biopsy of the skin. A pathologist may examine the skin under a microscope to determine the type of alopecia that is present.
Treatment of Alopecia in Dogs
There is no specific treatment for alopecia. Instead, treatment is aimed at eliminating the underlying cause of the problem.
Home Care and Prevention
Dogs with alopecia need to be kept groomed and free of fleas. If the hair loss is significant, some dogs may need to wear a sweater in the winter to protect them from cold weather. In the summer, sunburn may be a concern. If fleas are a problem, consult your veterinarian to discuss a comprehensive flea control program.
In-depth Information on Canine Alopecia
Nearly all diseases of the skin have the potential to cause alopecia. It is important to remember that it is normal to lose hair. Hair follicles are continually losing and developing new hairs. Alopecia can be separated into pruritic (itchy skin diseases) and non-pruritic.
Pruritic Causes of Alopecia
Fleas and flea allergy. Dogs with flea allergy tend to lose hair over the rump, on the back, hind legs, tail and belly.
Atopy. An allergy to airborne allergens such as pollens and molds, and food allergies tend to cause alopecia of the face, ears, feet, and other areas.
Scabies. Infestation with the Sarcoptes mange mite is an intensely itchy skin problem that causes alopecia of the ears, elbows, hocks, and other areas.
Other parasites such as Cheyletiella or lice cause pruritus and alopecia.
Pyoderma. An infection of the skin by bacteria or other infectious agents causes pustules. Pyodermas that involve hair follicles cause alopecia. Pyoderma may or may not be pruritic.
Dermatophyte fungi. Ringworm can cause either a non-pruritic or pruritic alopecia by damaging the hair shaft. The hair then breaks off and is shed into the animal’s environment where it can contact other animals and transmit the disease.
Non-pruritic Causes of Alopecia
Lack of production of thyroid hormone by the thyroid gland. Dogs with hypothyroidism tend to have sparse hair coats or patchy hair loss especially over the back and along the tail.
Hyperadrenocorticism. Cushing’s disease is an increase in the production of a hormone called cortisol by the adrenal glands. These dogs tend to lose hair in a symmetrical pattern and their skin will have a thin appearance. In addition, they have suppressed immune systems and are prone to pyoderma.
Other endocrine (hormonal) diseases such as imbalances in sex hormones produced by the adrenal glands can cause alopecia.
Autoimmune skin diseases are disorders where the body’s immune system attacks a component of the skin. These diseases can cause alopecia and may or may not be pruritic.
There are a number of other skin diseases that can feature alopecia, such as congenital hair follicle diseases that cause alopecia in the young puppy, and acquired hair follicle diseases that occur later in life. These are rare and may require the help of a veterinary dermatologist for diagnosis.
Your veterinarian will obtain a thorough medical history. Unlike most organ systems in the body, the skin can be directly observed. Therefore, what you have seen is very valuable in establishing a diagnosis. The breed, age, and sex of your animal may provide a clue. Expect to be asked about the age of your pet at the onset of the symptoms, the duration and severity of the symptoms, the degree of itching, medications previously used, and pattern of hair loss.
Your veterinarian will perform a thorough physical exam and skin exam. Particular attention will be paid to the pattern of hair loss and the distribution of the lesions. The appearance of the skin in the areas of alopecia will also be examined carefully.
Skin scrapings are commonly done to look for mites and other skin parasites. These scrapings are examined under a microscope.
Fungal cultures are often done to rule out dermatophytes (ringworm). Hair is plucked from the edge of the lesion and then is placed on a special culture media that turns from yellow to red in the presence of dermatophytes.
A trichogram may be done to characterize the alopecia. Hair grows in a cycle with a new hair being formed in the hair follicle to replace the hair that is mature and ready to be shed. Looking at hair under a microscope may tell the veterinarian if hairs are developing normally and may show broken hairs which would indicate a self-induced alopecia.
A hypoallergenic food trial or testing for allergen may be done to rule out allergy if the alopecia is related to pruritus.
A skin biopsy can be very helpful in diagnosing the cause of alopecia. The procedure may be done under general or local anesthesia. One or more small pieces of skin are taken from a skin lesion and submitted to a veterinary pathologist for examination. It is important for your veterinarian to send the sample to a pathologist with some expertise in dermatology. Even if the biopsy does not give a specific diagnosis, it may help to establish a path to diagnosis. For example, the results may indicate an allergic process, a hormonal process, or a bacterial process.
Blood tests for hypothyroidism, hyperadrenocorticism (Cushing’s disease), or another type of hormonal disease may be done.
The only way to successfully treat alopecia in dogs is to identify and treat the underlying cause. There are no symptomatic treatments.
If the alopecia is associated with pruritus, symptomatic treatments such as antihistamines, antipruritic shampoos, fatty acid supplements or corticosteroids may be temporarily helpful.
If alopecia is associated with pyoderma, antibiotics may help temporarily. Remember that pyoderma is nearly always secondary to another problem, so the underlying cause must still be found for long-term success.
Brushing dead and matted hair out of the coat may help to relieve symptoms that lead to alopecia.
Follow-up Care for Dogs with Hair Loss
Since there are so many different causes of alopecia, follow-up by the owner and communication with the veterinarian is critical. Administer all medications as instructed. Keep your dog’s coat clean and properly groomed. Observe closely for fleas. Flea infestation always makes alopecia worse.
Alopecia is the complete or partial lack of hair in any area of the skin where hair would normally be found. In dogs, it may be caused by self-trauma, hair follicle diseases or the failure of hair to grow after normal loss.