When a dog’s immune system, designed to protect them from external threats, mistakenly attacks their own body, it can lead to a range of health issues. One serious manifestation of this autoimmune response is the development of spontaneous, nasty lesions on the skin. These eruptions, often painful and blistering, signal that the body’s protective layers are compromised. When these autoimmune disorders target the epidermis and dermis, the skin’s layers can separate, resulting in debilitating sores.
The separation of skin layers can lead to the formation of blisters and pustules in the affected areas. These fragile pustules are prone to erosion, leading to crusting from discharged fluids and debris. Consequently, hair loss often occurs in these regions, and secondary bacterial infections are a common complication. In severe or recurring cases of atopic dermatitis, an underlying autoimmune skin problem is frequently suspected. Symptoms associated with atopy include persistent itching, sneezing, rashes, watery eyes, and excessive paw chewing. Unfortunately, by the time a definitive diagnosis is made, the initial trigger may no longer be apparent, complicating the diagnostic and treatment process.
While viruses are known triggers for autoimmune skin conditions in humans, their role in dogs is not yet well-documented. Although a genetic predisposition is recognized in human autoimmune disorders, it has not been definitively proven in dogs, though it is suspected to play a role. For instance, superficial pemphigus is observed more frequently in certain breeds such as the Akita.
Certain medications can also act as triggers in individual dogs. These include antibiotics like sulfonamide, penicillin, and cephalosporin. In some cases, topical medications used for external parasite control, such as those containing fipronil, amitraz, S-methoprene, dinotefuran, pyriproxyfen, or permethrin, may initiate the reaction. In such instances, discontinuing the medication may allow the skin to return to normal. However, other dogs require ongoing treatment to restore and maintain healthy skin.
Diagnosis of Autoimmune Skin Diseases
Autoimmune skin diseases in dogs, while not exceedingly common, do occur. A comprehensive patient history is crucial to rule out any drug-induced conditions. It’s also important to eliminate parasitic conditions as potential causes for the skin lesions. If these initial investigations yield no clear answers, a skin biopsy becomes the definitive method for diagnosing an autoimmune skin problem.
However, obtaining a diagnostically useful biopsy can be challenging. Ideally, the biopsy should capture a vesicle or pustule before it erodes. These lesions are exceptionally delicate and rarely found intact by the time a biopsy can be performed. Furthermore, any prior treatment can alter the biopsy results, potentially leading to an incorrect diagnosis.
Dr. William H. Miller Jr., professor emeritus of medicine, notes, “Even with my 40 years of experience, I can’t absolutely tell you that your dog has an autoimmune skin disease without the biopsy.” He further explains that the expense of a biopsy can be a significant barrier. In such situations, a veterinarian might initially opt for a trial of steroids. If the steroids are not sufficiently effective, or if the lesions recur after discontinuing the medication, a biopsy is then considered. A major drawback of this approach is the requirement to withhold steroid treatment for 14 to 21 days before the biopsy can be taken, as continued use can skew histological results and lead to a misdiagnosis.
Treatment Strategies for Canine Autoimmune Skin Disease
Typically, a combination of medications yields the fastest results in treating autoimmune skin diseases. Employing lower doses of individual drugs helps to minimize the risk of adverse side effects. Most treatment protocols begin with glucocorticoids (steroids like prednisone), administered alone or in conjunction with potent immunosuppressive drugs such as azathioprine or cyclosporine (Atopica).
Steroids are cost-effective and easy for owners to administer at home. However, their long-term use can lead to side effects. Initial side effects may include increased thirst and urination, and over time, they can escalate to more serious conditions such as diabetes mellitus, liver disease, and Cushing’s disease (iatrogenic hyperadrenocorticism).
For dogs requiring high doses of steroids initially, pulse therapy, which involves intermittent administration of large doses, may be recommended. This is followed by periodic dosing rather than daily lower doses. For milder or localized issues, topical steroids or immunomodulators like tacrolimus might be sufficient to maintain remission, at least temporarily.
Antibiotics are often necessary to manage secondary bacterial infections that can thrive in compromised skin. Performing cultures and sensitivity tests is recommended to identify the most effective antibiotic. Dogs suffering from atopy or other allergic dermatitis conditions benefit from concurrent treatment of those underlying issues, as well as any secondary yeast or fungal infections.
Emerging treatment avenues for canine autoimmune skin disease include acupuncture, often in conjunction with herbal remedies such as radix Curcuma wenyujin, Tripterygium wilfordii, Artemisia annua, and Berberis vulgaris.
Oclacitinib (Apoquel) shows promise, although further research is needed before its widespread recommendation. A significant advantage of oclacitinib is its generally lower incidence of significant side effects and higher overall safety profile compared to long-term corticosteroid use.
Some dogs may experience periods of remission, allowing for a gradual reduction in medication dosage, or even a temporary cessation of treatment. However, in most cases, the disease is likely to recur.
Finally, while the urge to shampoo a dog with skin issues is understandable, it is often best to refrain. According to Dr. Miller, “Shampoos have several problems. First, the commercially available ones contain 1% hydrocortisone, which isn’t very potent. The second issue with shampoos is that they can make things worse by the mechanical action needed to apply them and rinse them off. Autoimmune skin is more fragile than normal, and rubbing and rinsing can make it worse.”
Types of Canine Skin Autoimmune Diseases
This article was reprinted with permission from the Cornell University College of Veterinary Medicine’s DogWatch newsletter, published by Belvoir Media Group. Membership in the Riney Canine Health Center includes a complimentary subscription to DogWatch.
