The multimodal approach to canine atopic dermatitis

Pruritus can dramatically affect quality of life for both patients and their owners. Pet owners have reported that as the level of itch in their pet increases, their pet’s quality of life decreases. Different types of allergies can look the same, and patients can have more than 1 type of allergy, both of which can complicate the diagnosis. But the allergic workup is essential to provide comfort and minimize future flares.

Many issues can add to the frustration of owners of allergic dogs, including odor and visible lesions. Good client communication from the entire veterinary team can help owners work through the reality of managing a chronic disease, which often includes a multimodal approach.

Why atopic dermatitis occurs

Atopic dermatitis (AD) results from an inherited predisposition to develop hypersensitivities to environmental allergens that do not induce a problem in nonallergic individuals. Allergens can include dust mites, pollens, dander, insect particles, and molds.

The paws, axillae, abdomen, and face are common areas to develop pruritus and secondary lesions. These areas also tend to have less hair and increased exposure to common allergens, making topical therapy important. Cutaneous absorption of allergens is the primary route of exposure in canine AD.

Secondary infections

Infections are a secondary issue related to allergies. It can be confusing for an owner to understand how allergies and infections are different issues but impact one another. When owners have a clear picture of this relationship, they are often more willing to commit to multimodal therapy, including frequent bathing and ear flushes.

One of the biggest missteps when working up an allergic dog is neglecting to perform cytology to identify infection. Bacterial and yeast overgrowth on the skin or in the ears can increase the level of pruritus above the dog’s allergic itch. Performing cytology during an allergic workup and on rechecks is the foundation of allergic management. Areas of crusting, erythema, debris, alopecia, and lichenification should be sampled at every exam to identify the appropriate therapy and to prevent certain therapies from appearing to be ineffective due to presence of microorganisms.

Epidermal barrier function

Maintaining the stratum corneum (top layer of the epidermis) is essential for a healthy skin barrier. The stratum corneum contains corneocytes and intercellular lipid layers that serve as a border between a dog’s body and the dry environment. An abnormal epidermal barrier allows allergens to penetrate the skin and results in a cascade of cytokines and other inflammatory mediators causing pruritus. Therefore, a multimodal approach, including topical and systemic therapies to improve the epidermal barrier, is beneficial for dogs with AD.

Why topicals are important

Topical therapy should always be considered in management of canine AD. This includes during an active pyoderma event as well as for long-term maintenance to prevent recurrence. Topicals are particularly valuable for controlling chronic, recurrent cases of Staphylococcus infection to avoid development of methicillin resistance. Topical therapy may decrease the length of time systemic antibiotics are required or even eliminate the need for them altogether.

Certain topical therapies not only decrease bacterial populations and reduce surface recolonization, they help restore the epidermal barrier. The epidermal barrier has been shown to be abnormal in the skin of atopic dogs, even if it is nonlesional. This emphasizes the importance of utilizing restorative topical products even in well-controlled atopic patients. Used as a part of the maintenance protocol, these products can minimize the use of systemic allergy medications needed for management.

Lather up your atopic patients

Many topical formulations are available. However, bathing with high-quality shampoos is the preferred method if the dog will allow it and the client is able. Bathing removes allergens from the surface of the skin, and many ingredients include antimicrobial properties.

The most common antibacterial agent found in shampoos is chlorhexidine. It is important to use products that contain 3% to 4% chlorhexidine, such as DOUXO S3 Pyo (Ceva) if it is the sole active ingredient against Staphylococcus pseudintermedius. However, 2% chlorhexidine has been shown to have a synergistic effect with miconazole if a combination product is selected.

Bathing frequency depends on the severity of the case and the owner’s willingness or ability to bathe the pet. If you have a proactive owner, then many cases of pyoderma (even if resistant) can be managed with a bathing protocol alone. Cases of pyoderma typically benefit from frequent bathing (every 1 to 2 days) initially, followed by weekly maintenance. Contact time is another important aspect of a bathing protocol. Instruct owners to leave the shampoo on the skin for at least 5 to 10 minutes before rinsing thoroughly. If an owner is unable to bathe or additional topical therapy would be beneficial, alternate formulations such as mousses, sprays, and wipes are available.

Diet for epidermal barrier function

To avoid the use of more systemic medications, diets are available that can improve barrier function of atopic dogs through the use of nutrition. Diets include Royal Canin Skin Support, Hill’s Prescription Diet Derm Defense Canine, and Hill’s Prescription Diet Derm Complete. These diets are high in fatty acids and contain various vitamins that have been clinically proven to improve the epidermal barrier and decrease pruritus in dogs with AD. It is also easy for owners to implement at home if they are overwhelmed by the therapeutic plan.

Immunotherapy and antipruritics

Allergen-specific immunotherapy (ASIT) is the best long-term treatment for AD. It is formulated based on the results of intradermal or serologic allergy testing. ASIT consists of administering gradually increasing quantities of an allergen extract to a patient to improve the signs associated with subsequent exposure to the allergen. ASIT can take up to a year for full effect, and 60% to 70% of dogs have a positive response. When effective, therapy is usually life-long.

The use of systemic antipruritics is necessary in most cases of canine AD. This can range from keeping dogs comfortable while ASIT has time to become effective, managing seasonal flares, or long-term care in cases that require it. Systemic antipruritic options include oclacitinib (Apoquel; Zoetis), canine allergic dermatitis immunotherapeutic (Cytopoint, Zoetis), cyclosporine (Atopica; Elanco), or corticosteroids. It is important to weigh the benefits and risks of each therapy and to recognize that every patient has a unique response to different drugs.

How to make the best plan

Each multimodal plan is different depending on the owner and patient. With so many treatment options available for canine AD, the importance of addressing the epidermal barrier should not be overlooked. The use of topical therapy and nutritional supplementation should be considered with traditional antipruritic therapies to maximize the comfort and maintenance of dogs with AD.

References

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3. Cosgrove SB, Wren JA, Cleaver DM, et al. Efficacy and safety of oclacitinib for the control of pruritus and associated skin lesions in dogs with canine allergic dermatitis. Vet Dermatol. 2013;24(5):479-e114. doi:10.1111/vde.12047
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Ashley Bourgeois, DVM, DACVD, practices at Animal Dermatology Clinic in Portland, Oregon. She is an owner/shareholder and on the board of directors for the practice group, which has locations in California, Kentucky, Indiana, Georgia, Australia, and New Zealand. Bourgeois is passionate about educating veterinarians about dermatology and work-life balance through her podcast, speaking engagements, and social media presence (@TheDermVet).