This Is What's Causing Your Dog's Hair to Fall Out

Analysis by Dr. Karen Shaw Becker

dog hair loss

Story at-a-glance -

  • It’s natural for dogs to shed, and some shed much more than others, such as double-coated breeds
  • Genetics can also play a role in a dog’s shedding and hair growth patterns
  • There are also certain disorders that can cause hair to thin or fall out, and unlike normal shedding, they require veterinary attention
  • These disorders include itchy or infected skin, pressure sores and reactions to vaccines or medications
  • Hypothyroidism, Cushing’s disease and alopecia X can also cause hair loss

Believe it or not, the average dog has about 15,000 hairs per square inch, which is 15 times the density of human hair!1 Not only that, but your dog's hair covers her entire body, so is it any wonder she sheds all over the place? The truth is that all dogs shed, including so-called hypoallergenic breeds. Some breeds naturally shed more than others. The time of year, a warm versus cool climate, grooming habits and stress also influence shedding.

In addition, some double-coated dog breeds, including the German Shepherd, the Husky and the Malamute, "blow" their coats when warm weather arrives, resulting in a massive amount of shedding in which their undercoats come out by the handful. Genetics can also play a role in shedding and hair growth patterns. You're probably familiar with hairless dog breeds like the Chinese Crested, the Xolo (Mexican Hairless) and the American Hairless Terrier.

But what many people don't realize is there are certain breeds with an inherited tendency toward patchy or pattern baldness, typically on the lower neck, chest, back, thigh, between the eyes and ears or on the outer ear. These breeds include the Chihuahua, Dachshund, Doberman Pinscher, Italian Greyhound and Whippet. But what about a dog who doesn't fall into any of these categories, but whose coat is thinning or falling out?

8 Causes of Abnormal Hair Loss in Dogs

1. Itchy skin — It's extremely common for dogs with itchy skin to develop hair loss in areas where they've been obsessively scratching, licking, pulling or biting. Underlying causes for itchy skin with hair loss include allergies, bacterial and fungal skin infections, and parasitic infestations such as demodectic or sarcoptic mange.

2. Pressure sores — These sores, also called decubitus ulcers or bedsores, typically appear on a dog's elbows or other bony body parts that are frequently in contact with hard services. The skin in these areas can become rough, callused and hairless, and can even crack and bleed. Pressure sores are most often seen in older dogs, as well as large and heavy breeds.

3. Drug or vaccine reactions — Certain medications can trigger hair loss in dogs, for example, chemotherapy drugs. Injectable drugs, including vaccines, frequently cause hair loss at the injection site as the result of an inflammatory response to the substance(s) that was injected.

Long-term corticosteroid therapy can cause hair loss, and in high doses, can trigger a form of Cushing's called iatrogenic (medication induced) hyperadrenocorticism.

4. Hypothyroidism — This is a condition in which a dog's thyroid is underactive and unable to produce enough of the hormone thyroxine to meet the body's needs. Hypothyroidism is more common in medium to large dogs of both sexes who are between the ages of 4 and 10. Several breeds are genetically predisposed to the disorder, including:

Airedale Terriers

Golden Retrievers

Boxers

Greyhounds

Cocker Spaniels

Irish Setters

Dachshunds

Labrador Retrievers

Doberman Pinschers

Miniature Schnauzers

While some dogs with hypothyroidism have hair loss or fail to regrow clipped hair, the hallmark signs of the disorder are lack of energy, the need for frequent naps and exercise intolerance or loss of interest in running and playing.

5. Alopecia X — Alopecia X is an endocrine disorder characterized by an imbalance of sex hormones. It's essentially a cosmetic condition that is sometimes referred to as black skin disease because in addition to hair loss or an inability to regrow the coat, there is also hyperpigmentation, which causes the skin to darken over time. The condition is seen in both male and female dogs.

The primary sign of Alopecia X is the symmetrical and gradual loss of hair over the trunk and back of the thighs, but not the head or front legs. Breeds predisposed to the condition include the Chow Chow, Keeshond, Miniature Poodle, Pomeranian, Samoyed and the Siberian Husky.

6. Cushing's disease and atypical adrenal disease (hyperadrenocorticism) — Cushing's disease is a condition in which there is too much cortisol being produced by the adrenal glands. The disorder is most often seen in Terriers, Poodles, Dachshunds and the American Eskimo/Spitz.

Hyperadrenocorticism is a complex disease, and excessive cortisol can cause a diverse set of symptoms. In addition to hair loss, other common symptoms include:

Increased thirst and urination, which can lead to incontinence

Bruising

Increased panting

Thinning skin and change of skin color from pink to grey or black

Abdominal weight gain, despite a reduction in calorie intake

Irritability or restlessness

Atypical Cushing's disease occurs when there are elevations in circulating levels of sex hormones (usually metabolites of estrogen and progesterone) secreted by the adrenal glands without elevations in cortisol. This condition can cause skin and coat changes, including hair thinning and hyperpigmentation (dark skin).

7. Addison's disease (hypoadrenocorticism) — Addison's disease is the opposite of Cushing's, in that the adrenal glands produce fewer corticosteroid hormones than the body requires. The condition occurs predominantly in female dogs between the ages of 4 and 7.

Predisposed breeds include the Great Dane, Portuguese Water Spaniel, Rottweiler, Standard Poodle, and West Highland White and Wheaten terriers. Hypoadrenocorticism symptoms can be quite vague. In addition to hair loss in some dogs, other signs include weakness, depression, loss of appetite, vomiting, diarrhea, and increased thirst and urination.

8. Other potential causes — Nutritional deficiencies can cause hair loss in dogs, and so can stress. Mother dogs often "blow" their coat, which may be caused by the nutritional and physiological demands of giving birth and nursing a litter of pups. Anxious dogs, those with psychological or behavioral disorders (e.g., separation anxiety), and dogs with abusive backgrounds may also lose hair as a result of stress.

There are several reasons your dog's hair might start to thin or fall out, many of which can be caused by an underlying condition that must be identified and treated promptly. If you notice your dog's hair becoming thinner, falling out or failing to regrow after being clipped, it's important to make an appointment with your veterinarian as soon as possible.

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