The multimodal approach to canine atopic dermatitis
Itching can dramatically affect the quality of life of patients and their owners. Pet owners have reported that as their pet’s level of itching increases, their pet’s quality of life decreases. Different types of allergies can look the same and patients can have more than one type of allergy, both of which can complicate the diagnosis. But the allergic assessment is essential to provide comfort and minimize future outbreaks.
There are many issues that can add to the frustration of owners of allergic dogs, including odors and visible lesions. Good customer communication from the entire veterinary team can help owners cope with the reality of managing chronic disease, which often includes a multimodal approach.
Why atopic dermatitis occurs
Atopic dermatitis (AD) results from an inherited predisposition to develop hypersensitivity to environmental allergens which do not cause problems in non-allergic individuals. Allergens can include dust mites, pollens, dander, insect particles, and mold.
The legs, armpits, abdomen, and face are common areas for developing itching and secondary lesions. These areas also tend to have less body hair and increased exposure to common allergens, which makes topical treatment important. Skin absorption of allergens is the primary route of exposure in canine AD.
Infections are a secondary problem associated with allergies. It can be confusing for a homeowner to understand how allergies and infections are different but mutually influencing issues. When owners have a clear picture of this relationship, they are often more willing to engage in multimodal therapy, including frequent bathing and ear rinses.
One of the biggest mistakes when examining an allergic dog is neglecting to perform cytology to identify the infection. The overgrowth of bacteria and yeast on the skin or in the ears can increase the level of pruritus above the dog’s allergic itch. Performing cytology during an allergic assessment and during rechecks is the basis of allergic management. Areas of crusting, erythema, debris, alopecia and lichenification should be sampled at each examination to identify the appropriate treatment and to prevent some treatments from appearing ineffective due to the presence of micro- organizations.
Skin 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 the boundary between the dog’s body and the dry environment. An abnormal epidermal barrier allows allergens to enter the skin and results in a cascade of cytokines and other inflammatory mediators causing itching. Therefore, a multimodal approach, comprising topical and systemic therapies to improve the epidermal barrier, is beneficial for dogs with AD.
Why hot topics matter
Topical treatment should always be considered in the management of canine AD. This includes during an event of active pyoderma as well as for long-term maintenance to prevent recurrence. Topicals are particularly useful for controlling chronic and recurrent cases of Staphylococcus infection to prevent the development of methicillin resistance. Topical treatment can reduce the length of time systemic antibiotics are needed or even eliminate their need altogether.
Some 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 though it is not lesion. This underscores the importance of using topical restorative products even in well-controlled atopic patients. Used as part of the maintenance protocol, these products may minimize the use of systemic allergy medications required for management.
Lather your atopic patients
Many topical formulations are available. However, bathing with high quality shampoos is the preferred method if the dog allows it and the client is able. The bath removes allergens from the skin’s surface and many ingredients have antimicrobial properties.
The most common antibacterial agent in shampoos is chlorhexidine. It is important to use products containing 3-4% chlorhexidine, such as DOUXO S3 Pyo (Ceva) if it is the only active ingredient against Staphylococcus pseudointermedius. However, 2% chlorhexidine has been shown to have a synergistic effect with miconazole if a combination product is selected.
The frequency of baths depends on the severity of the case and the owner’s willingness or ability to bathe the animal. If you have a proactive owner, many cases of pyoderma (even resistant ones) can be managed with a bathing protocol alone. Pyoderma cases usually benefit from frequent bathing (every 1 to 2 days) at first, followed by weekly maintenance. Contact time is another important aspect of a bathing protocol. Ask owners to leave shampoo on skin for at least 5-10 minutes before rinsing off thoroughly. If an owner is unable to bathe or if additional topical treatment would be beneficial, alternative formulations such as foams, sprays and wipes are available.
Diet for epidermal barrier function
To avoid the use of more systemic drugs, diets are available that can improve the 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 rich in fatty acids and contain various vitamins that have been clinically proven to improve the epidermal barrier and decrease itching in dogs with AD. It is also easy for homeowners to implement it at home if they are overwhelmed with the treatment plan.
Immunotherapy and antipruritics
Allergen-specific immunotherapy (ASIT) is the best long-term treatment for AD. It is formulated on the basis of the results of intradermal or serological allergy tests. ASIT involves administering gradually increasing amounts of an allergenic extract to a patient to improve the signs associated with subsequent exposure to the allergen. ASIT can take up to a year to be fully effective, and 60-70% of dogs have a positive response. When effective, therapy usually lasts a lifetime.
The use of systemic antipruritics is necessary in most cases of canine AD. This can range from comforting dogs while ASIT has time to become effective, to managing seasonal flare-ups, or providing long-term care in cases that require it. Systemic antipruritic options include oclacitinib (Apoquel; Zoetis), immunotherapeutic canine allergic dermatitis (Cytopoint, Zoetis), cyclosporine (Atopica; Elanco) or corticosteroids. It is important to weigh the benefits and risks of each therapy and to recognize that each patient has a unique response to different medications.
How to make the best plan
Each multimodal plan is different depending on the owner and the 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 treatment and nutritional supplementation should be considered with traditional antipruritic therapy to maximize the comfort and maintenance of dogs with AD.
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Ashley Bourgeois, DVM, DACVD, practices at the Animal Dermatology Clinic in Portland, Oregon. She is the owner / shareholder and a member of the board of directors of the practice group, which has offices in California, Kentucky, Indiana, Georgia, Australia and New Zealand. Bourgeois is passionate about educating veterinarians on dermatology and work-life balance through his podcast, speaking engagements and social media presence (@TheDermVet).