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.
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 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 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.
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.
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.
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.
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.
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.