Hair Loss in Dogs
by Dr. Audrey Harvey, BVSc (Hons)
Hair loss in dogs is fairly common and is a frequent reason why they are taken to their veterinarian. Alopecia, the scientific name for hair loss, occurs for many different reasons in dogs. Although the reasons for alopecia are many, here are the 10 main causes...
10 Common Causes of Hair Loss in Dogs
Ringworm is caused by a fungal infection, and leads to hair loss and gray scaly skin. It isn't itchy, but it is highly contagious to both you and your other pets. To learn more about ringworm treatment for dogs see: Ringworm in Dogs.
2. Hotspots and Allergies
Many dogs suffer from skin allergies and as they scratch and chew their inflamed skin, they break off their hair, leaving bald patches. A hot spot is a very acute skin infection which appears within a matter of hours, and is extremely itchy and painful. Affected dogs scratch at it to relieve the irritation, which results in a red raw hairless sore. See: Dog Allergies.
3. Acral Lick Dermatitis
Another common cause of hair loss in dogs is Acral Lick Dermatitis, which is a chronic skin problem caused by excessive licking, and it usually affects the skin of the lower leg. The licking leads to itching and secondary infection, which leads to more licking. The result is initially thickening of the skin and hair loss, which progresses to ulceration.
The cause of Acral Lick Dermatitis isn't known, but some theories are that underlying nerve damage, pain or tissue damage has triggered the initial licking, and then the vicious cycle of licking, itching and more licking commences. Because dogs are known to lick a lot when they are anxious, it is thought that anxiety or even an obsessive compulsive type of disorder may also be involved.
4. Parasites (Fleas/Demodex)
Little parasites living in and on skin are notorious for causing hair loss in dogs. The two most common parasites are fleas and demodex mites.
Fleas are blood suckers, and their bite will make a dog itch. As a dog nibbles at his itchy spot, he will snap off his hair, leaving bald areas. Some individuals become allergic to fleas and their excessive scratching leads to skin trauma and secondary infection.
Demodex is a little mite that lives inside hair follicles. They are present in all dogs but in some individuals, they multiply and cause patches of hair loss. It's often seen in dogs with a lowered immune system, such as young pups or elderly dogs with chronic disease. See: Dog Parasites.
5. Hormonal Hair Loss in Dogs
Hair loss in dogs due to hormonal disorders tends to affect the body, leaving the head and legs relatively normal. It is usually symmetrical, meaning both sides of the body are affected in the same way. The hair loss isn't usually itchy, and other symptoms such as excessive thirst or weight gain are often present.
The most common hormonal disease in dogs is hypothyroidism, which occurs because the thyroid gland doesn't produce enough hormone. Around 40% of dogs with this condition have hair loss.Cushing's Disease is associated with an excess of cortisol in the body. This can happen in association with an adrenal gland or pituitary gland tumor, or if a dog is prescribed corticosteroid tablets for long periods of time.
6. Pressure Sore Calluses
These develop on parts of the body over bony prominences such as the elbows or hips, because of increased pressure on the skin. They are thick hairless areas which protect the tissues underneath. There is usually no pain or inflammation, and they are not itchy. However, if they are abraded when the dog lies on rough surfaces, bacteria can multiply leading to infection. Padded bedding is an important part of treating pressure sore calluses in dogs.
7. Zinc Responsive Dermatosis
Zinc Responsive Dermatosis has very characteristic symptoms – hair loss and crusting around the muzzle and eyes, and on the ears and hocks. It is caused by a zinc deficiency. In some cases, a zinc deficient diet is responsible, and zinc supplementation is helpful. In Arctic breeds such as the Siberian Husky, there is an inherited condition which interferes with the absorption of dietary zinc.
You need to be careful when you give zinc supplements to your dog, because they can have too much of a good thing. Zinc toxicity is a very real possibility.
8. Color Dilution Alopecia
Color Dilution Alopecia occurs because there is an abnormality in a dog's hair follicles. It affects those dogs with fawn or blue coats. These colors are diluted brown or black coats, hence the name color dilution alopecia. It is hereditary, and in most cases it doesn't cause any skin problems; it just looks unusual. However, frequent skin infections may occur, and these will need treatment.
9. Alopecia X
Alopecia X is so named because veterinarians don't fully understand its cause. It is most likely to occur in Chow Chows, Pomeranians, Keeshonds and Miniature Poodles. Long primary hairs gradually fall out, leaving a soft fluffy undercoat, much like that of a puppy. Over time, it too is progressively lost.
This type of hair loss in dogs occurs primarily on the body, which suggests a hormonal cause but blood tests for the common hormonal alopecias are normal. The disease may be linked with the sex hormones, because neutering often has a positive result.
Alopecia X is not itchy or painful. It only affects your dog's appearance, so there is often no need for any treatment.
10. Dog Pattern baldness
Dog Pattern baldness is a thinning of the hair that occurs gradually, and progresses to alopecia. In the most common form, Dachshunds, Greyhounds, Whippets and Boston Terriers lose hair on the temples, the ears, the underside of the neck, the chest and abdomen, and down the back of the thighs.
This condition is thought to be hereditary, and although it doesn't cause dogs any problems at all, it's a good idea not to breed from affected animals.
Reaching a Diagnosis
It can be difficult to work out the cause of hair loss in dogs particularly if they are suffering from one of the less common conditions.
Your veterinarian can develop a list of possible diagnoses based on the appearance of your dog's skin. Are fleas present? Is there evidence of licking on the legs? How quickly did the hair loss appear? What parts of the body are affected? Sometimes a clinical examination will be enough to reach a diagnosis. This can be the case with conditions such as flea allergy dermatitis, and hot spots. In most cases though, further testing is needed.
Skin scrapings are usually taken and examined under the microscope, to look for demodex. A Wood's lamp is the first step in looking for evidence of fungal infection. If there is any indication that hormonal problems may be involved in your dog's hair loss, then blood tests will be done to check hormone levels. Hypothyroidism is diagnosed by measuring the amount of thyroid hormone in the blood. An ACTH stimulation test checks the adrenal gland's ability to produce cortisol, and is useful in confirming or ruling out a diagnosis of Cushing's Disease.
Sometimes the only way to be sure of the cause of hair loss in dogs is to take a skin biopsy. This is usually done under local anesthetic, and will give you a result in about 48 hours.
Treating Hair Loss in Dogs
Management of alopecia in dogs must be directed at the underlying cause. This means that it is important that you have a proper diagnosis before you start any treatment.
It may be necessary to give your dog medication to treat his alopecia, such as zinc tablets, thyroid hormone supplements, antibiotics, or anti-inflammatory drugs.
He may require surgery; one example is the positive response to neutering that is seen in many cases of Alopecia X.
Treatment can also include insecticides such as flea control products and chemicals to kill demodex mites.
No matter what the cause of your dog's alopecia, omega fatty acids can help reduce inflammation, alleviate dryness, and generally improve the condition of his skin and coat.
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