By Rebecca Mount, DVM, DACVD

Although there have been many advancements in therapeutic options for atopic dermatitis over the last 10 years, allergy testing and allergy-specific immunotherapy (ASIT) still remains one of the safest long-term treatment options available. Unlike other therapies, immunotherapy can both reduce the clinical signs of atopic dermatitis and slow progression of the disease.¹

However, despite its safety profile and fairly high efficacy, ASIT is often underutilized in managing canine and feline atopic dermatitis. There are many common misconceptions about allergy testing and the benefits of immunotherapy, which may deter many veterinarians from recommending this therapy route. However, a better understanding of the safety and benefits may make this treatment option more alluring to pet owners.

Myth No. 1: Tests diagnose environmental allergies

Determining atopic dermatitis in dogs and cats is considered a diagnosis of exclusion.² In order to confirm the diagnosis of environmentally triggered atopy, other causes of allergic inflammation, including parasites and food triggers, must be ruled out.

Unfortunately, positives on an intradermal skin test (IDAT) or serology test do not confirm a diagnosis of atopic dermatitis. False positives on allergy tests can be caused by irritant reactions, seasonal sensitization, or non-immunologic triggers of histamine release.³ Since serology is based on circulated IgE levels, it is more likely than IDATs to show positives in non-allergic dogs.

Therefore, positive reactions on a skin test or serology should always been looked at in conjunction with the whole clinical picture to determine if the results are fitting with the pet's clinical history and allergic signs. It is important to remember allergy testing is primarily used to direct formulation of immunotherapy in confirmed cases of atopic dermatitis.

Myth No. 2: The pet is too young to be allergy tested

Many pet owners and some veterinarians believe allergy testing is reserved for older dogs or refractory cases that do not respond to other therapy options. Allergy testing is a viable option for allergic pets regardless of age. In fact, there are many benefits to testing younger animals, including faster reduction of long-term drug use, improved response to immunotherapy, and improved cost to benefit ratio of testing and immunotherapy.

We know ASIT can be beneficial in the hard-to-manage cases, but it should also be considered in even mild ones. Since immunotherapy can actually slow progression of disease, it could delay or even prevent the progression from mild allergic disease to more severe allergic signs.

Furthermore, with uncommon to rare side effects noted with immunotherapy, many owners are drawn to the potential of a non-drug treatment plan for long-term control of their pets' allergies.

Myth No. 3: Immunotherapy should work quickly

When discussing immunotherapy as a possible treatment option, it is important to discuss the expected timeline for onset of efficacy and to manage owners' expectations. Immunotherapy ameliorates clinical signs associated with allergies by shifting the immune response from an inflammatory Th2 response to more tolerant Th1 response, which is not an immediate process.

In most cases, there will be a delay of four to six months up to 12 months to see the onset of efficacy of immunotherapy. Response rates to ASIT are reported to be around 60 to 80 percent.³ It is generally believed there will be at least a 50 percent or greater improvement in clinical signs in the majority of pets on immunotherapy.³ However, response to immunotherapy may range from controlling all allergic signs as a sole therapy to allowing for reduction, but not discontinuation, of drugs needed for control. While this route may take a little more patience, the long-term safety benefits make it strongly worth considering.

Myth No. 4: It's the most expensive treatment option

Although the upfront cost of testing can be a bit daunting, the long-term expense of immunotherapy is generally on par with the monthly cost of other long-term medications. Additionally, since immunotherapy has minimal adverse side effects or systemic metabolism, bloodwork monitoring is not required as it is with many drug-based therapy options.

Myth No. 5: Immunotherapy only comes in injections

Historically, immunotherapy was only available in a subcutaneous injectable (SQIT) formulation, which required weekly to monthly injections.

For many owners, the thought of having to administer injections to their pets or take their pets into their veterinarians frequently for injections was daunting and deterred them from considering immunotherapy as a treatment option. Many companies and dermatologists now offer a sublingual (SLIT) formulation for ASIT. SLIT is an aqueous allergen formulation that is delivered to the oral mucosa usually once to twice daily.

Myth No. 6: There are no options to immunotherapy

A recent study⁴ found one of the biggest barriers for recommending immunotherapy is easy access to a dermatologist.⁴ Intradermal skin tests are considered the ideal test for allergy testing.

However, serology is a great option for allergy testing when it is not feasible to perform skin testing in a primary veterinary practice or referral to a dermatologist is not an option. Serology does offer some benefits over IDATs, including no sedation, no shaving or clipping, shorter withdrawal times, and wide availability. In many cases, serology is a great option to pursue immunotherapy, especially if skin testing is not available.

Myth No. 7: All allergens can be removed

Many owners pursue allergy testing with the goal of removing offending allergens from the pet's environment. It is important to point out elimination is often impractical, if not impossible, and the goal of allergy testing is to direct formulation of immunotherapy. A common statement in practice is, "if it is in your pet's ZIP code, it is in your pet's life."

While there are some items, like wool rugs in wool-reactive pets, that can be removed based on the results, it is important to remember we use ASIT to help desensitize pets to the allergens impossible to remove from their environment.

Unfortunately, atopic dermatitis is a challenging, life-long disease and there is no single therapy universally effective in all pets. However, immunotherapy, with its strong safety profile, is an alluring treatment option for many pet owners who may not be comfortable with long-term use of anti-pruritic/anti-inflammatory medications, or for pets which are not well controlled with drugs alone.

In-depth discussions about the expectations and benefits of immunotherapy prior to testing is important to help owners better understand the process and make the long-term commitment. As always, when treating allergies with immunotherapy it is important to remember it is marathon, not a sprint, and good things come to those who wait!

Rebecca Mount, DVM, was born and raised in Albuquerque, N.M. She earned her bachelor of science in biology from the University of New Mexico in 2005 and her doctorate of veterinary medicine from Colorado State University College of Veterinary and Biomedical Sciences in 2009. Following graduation, Dr. Mount completed a challenging internship in small animal medicine and surgery at Garden State Veterinary Specialists in New Jersey. Mount began her residency with Dermatology for Animals in 2010 and became a diplomate of the American College of Veterinary Dermatology in 2014.

References

1. Olivry, T, DeBoer DJ, Griffin C et al. The ACVD task force on canine atopic atopic dermatitis: foreword and lexicon. Vet Immunol Immunopathol. 2001; 81: 143-146.
2. Hensel, P, Santoro, D, Favre, C et al. Canine atopic dermatitis: detailed guidelines for diagnosis and allergen identification. Vet Dermatol. 2020; 31: 271-e98
3. Miller, W, Griffin C, Campbell KL. Mueller and Kirk's Small Animal Dermatology, 7th edition. St. Louis MO: Elsevier Mosby. 2013; 363-431.
4. Flanagan, S, Schick, A, Lewis, T. "A pilot study to identify perceived barrier and motivating factors of primary veterinarians in the USA for specialty referral and management of atopic dermatitis with allergen-specific immunotherapy." Vet Dermatol. 2020: 31, 371-e98