Definition of Alopecia
Hair loss, technically called “alopecia,” is broadly defined as any deficiency in a dog’s normal hair coat. Alopecia doesn’t refer only to hair loss; it also includes coat defects from failure of hair to grow in the first place. Many medical conditions involve hair loss, including color dilution alopecia, seasonal flank alopecia, alopecia X (“black skin disease”), acanthosis nigricans, follicular dysplasia, congenital hypotrichosis, pattern baldness and pituitary dwarfism. Some have a genetic component. External parasites, fungal and bacterial skin infections, certain drugs, hormonal/endocrine imbalances such as Cushing’s Disease, Addison’s Disease, hypothyroidism, hyperthyroidism, allergies, stress, poor nutrition, lactation and cancer can all cause hair loss, with or without redness, itchiness, scabbing, scaling or bleeding. Because hair loss typically is associated with an underlying medical disorder, annual veterinary examinations can help identify and manage the problem before it becomes out of hand. These tests are especially important for older dogs.
Causes of Canine Alopecia
There is no particular age or sex predisposition to the development of alopecia, although certain dog breeds do seem at increased risk for certain kinds of alopecia. Doberman pinschers and many other breeds are prone to developing color dilution alopecia. Recurrent seasonal flank alopecia tends to occur in Boxers, Bulldogs, and Airedale terriers. Alopecia X (also called adrenal reproductive hormone imbalance and sometimes called “black skin disease”) occurs more commonly in plush-coated breeds such as the Pomeranian, Chow chow, Keeshond, and Miniature poodle, and also in Arctic breeds (Samoyed, Siberian husky, Alaskan malamute).
Some of the more common causes of alopecia in dogs are described below.
Parasites
External parasites are notorious for causing alopecia in dogs. Fleas, ticks, lice and mites can all cause intense itching and scratching which leads to hair loss. Parasites can also physically damage the hair follicles, and allergic reactions to the parasites can cause hair loss as well. Demodectic mange (caused by various species of mites that live within the hair follicles) causes localized to generalized hair loss with redness and mild scaling.
Fungal Infections
Fungal infections of the skin (called “dermatophytosis”) can cause partial to complete alopecia with scaling and with or without associated redness. Some fungal infections are zoonotic, which means that they have the potential to cause skin lesions in people.
Bacterial Infections
Bacterial skin infections – especially those caused by Staphylococcal species – can cause alopecia with redness, crusting and circular patterns of hair loss. Bacterial folliculitis is the most common cause of multifocal alopecia in dogs.
Hormonal/Endocrine Imbalances
Several different endocrine disorders commonly contribute to alopecia. Hyperadrenocorticism (Cushing’s disease, or iatrogenic hyperadrenocorticism caused by veterinary corticosteroid administration), hypoadrenocorticism (Addison’s disease), hypothyroidism, hyperthyroidism, hyperestrogenism (in females) and hypoandrogenism can all result in some form of alopecia if the underlying condition is not controlled. Many dogs have focal hair loss around the genital and flank regions following spay or neuter procedures. Testicular neoplasia (cancer) can also cause hormonally-based alopecia.
Allergies
Immune-mediated reactions to certain foods, chemicals, pollens, grasses and many other potential allergens are among the most common causes of hair loss in dogs.
Inherited Conditions
Some types of alopecia have a genetic basis. These include: acanthosis nigricans, Alopecia X (also called adrenal reproductive hormone imbalance and sometimes simply “black skin disease”), follicular dysplasia, color dilution mutant alopecia, congenital hypotrichosis, pattern baldness and pituitary dwarfism, among others.
Reactions to Medication or Injections
Drug reactions can lead to hair loss. For example, chemotherapeutic treatments for cancer commonly cause alopecia. Hair loss often occurs at injection sites, usually caused by an inflammatory reaction to the substance that was injected. Rabies vaccines have been known to cause patchy hair loss around the injection site 2 to 3 months after being given.
Stress and Nutritional Deficiencies
Nutritional deficiencies and other causes of stress can cause alopecia. Bitches that are nursing puppies often “blow their coat” – a type of alopecia probably caused by the nutritional, physical. and emotional strain associated with whelping and lactation. Dogs that are especially anxious or high-strung, have psychological or behavioral disorders (separation anxiety, etc.), or who have abusive backgrounds may also lose hair as a result of stress.
Preventing Alopecia
Responsible Breeding
Certain breeds or family lines of dogs have an increased risk of developing alopecia. For example, small-breed dogs with plush coats and certain Arctic breeds are prone to developing Alopecia X, also known as adrenal reproductive hormone imbalance or black skin disease. Doberman pinschers are genetically predisposed to color dilution alopecia. Responsible breeders will eliminate affected dogs from their breeding programs.
Parasitic Alopecia
Many cases of alopecia in dogs are caused by external parasites. Using preventative parasite control will reduce or eliminate parasitic infestation and the alopecia that often accompanies it. Owners of dogs that live in (or frequently visit) areas infested with fleas and ticks should regularly use flea and tick repellents, even if their dogs have not yet become infected by those parasites. Maintaining a clean and hygienic environment will also reduce the risk of alopecia associated with fleas, ticks, lice and mites.
Hair Loss Due to Underlying Medical Conditions
Alopecia is often caused by an underlying medical condition. Annual veterinary examinations with regular blood and urine tests will help identify underlying endocrine, hormonal, immune-mediated or other medical conditions that can cause or contribute to alopecia. These tests are especially important for older dogs. Spaying and neutering of companion animals can also greatly reduce the risk of alopecia.
Nutrition and Other Prevention
Hair loss cannot always be prevented, nor can it always be “cured.” However, providing a safe, clean, stress-free environment and a high-quality diet with free access to fresh water will go a long way to helping companion animals maintain a healthy hair coat.
How Alopecia Affects Dogs
Alopecia is one of the more common complaints of dog owners. How alopecia affects a dog depends upon the underlying cause of the condition. Hair loss (or failure to grow) can occur anywhere on the body of a dog of any age, breed or gender, including on the face, around the eyes, on the back, near the base of the tail or on the flank. The hair abnormality may occur on its own without any apparent cause or other clinical signs. Alternatively, the absence of hair may be accompanied by scratching, redness, pustules or other skin changes. Alopecia can appear symmetrically in discrete but well distributed patches, or it can have no pattern at all.
Symptoms of Alopecia
One of the most baffling things about alopecia is the vast number of ways that it can present. It can occur acutely or be slowly progressive. It can happen in isolation or with localized or generalized hair loss but no other clinical signs. The skin may appear normal, and the dog may act completely normal as well. Some cases of alopecia never progress. The affected dog simply loses hair, and the hair does not grow back. In other cases, hair loss may spread across the body and become generalized, or it may become patchy.
Symptoms In Addition to Hair Loss
When hair loss is accompanied by other clinical signs, owners usually notice itching, scratching, chewing and changes to the appearance or condition of the skin itself. The skin in areas of hair loss can become red, irritated and inflamed, or it can darken. In many cases, the affected skin becomes crusty, thickened, and raised. It can also become thinner. Sometimes, the skin becomes oily and greasy, and pustules or other skin lesions can develop. In severe cases, dogs can develop blisters, weeping sores and hot spots, which are prone to developing secondary bacterial infections.
Which clinical signs a particular dog develops depends upon the underlying cause of the alopecia. The specific signs are important to help the veterinarian establish a correct diagnosis.
Treatment Options
Alopecia is usually a sign of an underlying disorder, which must be diagnosed accurately in order for effective treatment to begin. If the hair loss is accompanied by scratching, pustules, hot spots or other lesions, it may be appropriate to apply topical medications to manage and hopefully alleviate the discomfort caused by these conditions even before the actual cause of the alopecia is determined. The veterinarian may prescribe ointments, creams, lotions, shampoos or other soothing treatments to calm any inflammation associated with alopecia. She also may recommend oral or topical antibiotics, antihistamines and/or anti-inflammatories as part of an initial treatment regimen.
Parasitic Alopecia
There are a number of topical medications to treat alopecia caused by external parasites. Flea and tick control, and shampoos or other products that kill mites, lice or fungi, are generally quite effective in resolving parasitic alopecia, although it can take weeks to months for the hair to grow back completely.
Alopecia Due to Endocrine Disorders or Hormonal Imbalance
Alopecia caused by endocrine or hormonal abnormalities is managed by treating the underlying disorders. For example, alopecia associated with hyperthyroidism or pituitary dwarfism can be treated with lifelong hormone replacement medication. Spaying and neutering can be successful treatments for hair loss caused by certain other hormonal imbalances, or even stress.
Allergic Alopecia
There are a number of treatment options for alopecia caused by immune-mediated reactions. These include medicated shampoos, topical and oral anti-inflammatories and antihistamines, and corticosteroid therapy. Of course, if a veterinarian can identify the cause of the reaction and remove the allergen from the dog’s environment, allergic alopecia should resolve in short order.
Other Treatments
Essential fatty-acids, Vitamin D, and oral melatonin supplementation have been found to be safe and variably effective in stimulating hair regrowth and improving overall coat condition in dogs.
Prognosis
The prognosis for recovery from alopecia is good in most cases, if the underlying cause of hair loss is identified and treated. If the skin has suffered extensive scarring, hair regrowth will be more limited.
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