By Dr. Becker
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.
But what about a non-itchy dog with none of those conditions whose hair is thinning or falling out?
8 Causes of Hair Loss in Dogs
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 benign 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.
2. Pressure sores
These sores, also called decubital 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.
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
✓ Cocker Spaniels
✓ Irish Setters
✓ 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.
4. 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 signs to watch for include:
✓ Increased thirst and urination, which can lead to incontinence
✓ 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).
5. 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.
6. Alopecia X
Alopecia X is an endocrine condition that has a number of other names, including black skin disease. It's a cosmetic skin condition characterized by areas of hair loss and hyperpigmentation, and it occurs in both male and female dogs.
Alopecia X is caused by an imbalance of sex hormones that causes hair loss or inability to regrow the coat, coupled with insufficient production of melatonin, which is what causes the skin to darken over time.
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.
7. 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 (e.g., prednisone) therapy can cause hair loss, and in high doses, can trigger a form of Cushing's called iatrogenic (medication-induced) hyperadrenocorticism.
8. Other causes
Nutritional deficiencies can cause hair loss in dogs, and so can stress. Mother dogs often "blow their coat," which is likely 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.
As you can see from the list, 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.