Wednesday, April 17, 2019

Canine Atopic Dermatitis ~ David Kleisch, DVM, MBA

Spring time. Warmer weather, longer days, and gorgeous blooms. Living in North Carolina, we typically group all of these wonderful things with the all too common “allergies”. Everyone knows someone who exhibits allergies, and they are driven by a little substance called the allergen.

Allergens are typical harmless substances that are capable of triggering a response of the immune system, and that response can result in an allergic reaction. For you and me, that can be manifested as itching, sneezing, watering of the eyes, stuffy nose, and then the coughing/sneezing. For our canine companions, allergies are typically manifested as skin irritation and dermatitis, triggering an over-active immune system and called “Canine Atopic Dermatitis”.
Atopic dermatitis in dogs (AKA allergic dermatitis or canine atopy) is a hypersensitivity or over-reaction to any variety of commonplace and otherwise harmless substances in the environment. These allergens can range from environmental plant pollens, to house hold dust mites, storage mites, or mold spores. Most allergic dogs begin to show signs between one and three years of age, but the age is not specific to the patients.
Presenting Clinical Signs

Atopic dogs will scratch, chew, lick, or rub areas of the body such as their paws, face, and rear end. They can have recurrent skin or ear inflammation and typically have secondary skin infections. This itchy behavior, or pruritus, can cause hair loss and reddening and thickening of the skin. The cardinal location of skin thickening and redness in canines is around the eyes, under the arms, between the legs and around the tail base. Dr. Olivery at North Carolina State University, Department of Dermatology describes these areas as the target zones, meaning while they are the hallmark areas they are not the only areas. If you notice your dog itching/scratching in general, it is recommended to have them evaluated for the underlining cause, and potentially for atopic dermatitis.

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Dr. Olivery at NCSU Dermatology shows classical presentation for canine atopic dermatitis. a Diagram showing the distribution of skin lesions (red) in dogs with classical phenotypes. b-e Skin lesions in a crossbred dog with AD of classical phenotype. From a distance, lesions can hardly be seen (b), but erythema, hyperpigmentation and self-induced alopecia are visible on the axillae, groin (c), periocular and perilabial areas (d), and flexures of the elbows (e; right [R] and left [L]). (2) 1

Diagnosis

Unlike other diseases where tests can be performed, atopic dermatitis is a clinical diagnosis. Doctors typically form diagnoses based on history, clinical symptoms present, and the seasonality of the symptoms. Many clients ask if we can complete allergy testing. Yes, we can complete an allergy test, but this is not a test for atopic dermatitis. This test is for identification of the allergen that is causing the increase and over-activity of the immune system. This is beneficial because we can remove this allergen, however, this does not treat the disease.

Treatment
If a dog is diagnosed with atopic dermatitis, there are broad treatment options and targeted therapy options. Additionally, specific treatment for any secondary infection is a cornerstone of the treatment plan.  
  • Avoiding allergens: This is the HARDEST to do, and it is usually impossible to remove all allergens from a pet's environment, because even a small amount can trigger a dog’s allergies. However, bathing can help remove allergens from the skin. A hypoallergenic cream rinse or spray can re-moisturize the skin after bathing.
  • Medications: A variety of anti-allergy drugs are available. These drugs include antihistamines, steroids (cortisone), cyclosporine, and newer drugs such as oclacitinib (Apoquel). However, these medications all have side effects, and they have come out with biologics that treat canine symptoms without any side effects. These medications are “immunotherapy” medications, and Cytopoint is the best Immunotherapy known.  
  • Allergen specific immunotherapy: Immunotherapy involves giving a series of diluted allergens based on what your dog is allergic to. Allergen-specific immunotherapy makes dogs less sensitive to their allergens, and 60-80% of patients improve on immunotherapy. However, improvement on immunotherapy takes time, and it is important to try the immunotherapy for several months so it can take effect. When helpful, immunotherapy is usually continued life-long but can be given less frequently over time.

Treating any Secondary Infections

Atopic dermatitis will likely have an associated opportunistic secondary infection. Secondary infections involve bacteria (usually Staphylococcal) and/or yeast (Malassezia) at the site of the itchiest areas on the body. These organisms live naturally in the skin, but when the skin is irritated, they gain access to inner tissue layers and proliferate. Sometimes they actually come to generate further allergic response in the skin. These infections tend to recur and are the usual cause of recurrence of itch symptoms in a patient who was previously controlled.
  • Broad Spectrum Therapy: When atopic dermatitis is first diagnosed, the goals of therapy are balancing the treatment of the infection, restoring the comfort of the animal, and decreasing the inflammation (if present). For major flare-ups, using a corticosteroid as a broad spectrum therapy is rrecommended. Corticosteroids (prednisone, prednisolone, triamcinolone, dexamethasone, etc.) are very useful as the first line of defense against itchy skin. While we use these for initial flare-ups, the broad spectrum therapy includes undesirable side effects when used long term. So, while we use these for acute flare-ups, these medications are not great management drugs for atopic dermatitis. Therefore, we consider this broad spectrum therapy of steroids useful for acute flare-ups, then once controlled, we move to focal and targeted therapy. 
  • Targeted Therapy: Targeted therapy ranges from immunotherapy (Allergy injections) to pharmaceutical therapy, including medications like Cyclosporine or Apoquel, or biologics similar to Cytopoint. These are decided on a combination of clinical signs and trial and error, along with the ease of medication administration for the owner and patient. As mentioned above, the best way to manage atopic dermatitis is to remove the allergen. Unfortunately, this is impossible. So, we can attempt to desensitize the patient to the allergens with allergen immunotherapy. 
  • Desensitization (Allergen Specific Immunotherapy): Allergy Shots are a great treatment of choice for atopic dermatitis. All the other medications are basically just itch relief; only desensitization actually changes the immune system. Most dogs experience some improvement but not all dogs experience great improvement. Allergy shots require approximately 8 to 12 months to begin working. 
       ~ An estimated 33% (1/3) of atopic dogs will not respond 
       (these are usually the animals allergic to multiple allergens).

       ~ 25% will require prednisone or similar steroid at least at 
       some times.

       ~ You will most likely have to give the allergy shots yourself.

       ~ Referral to a veterinary dermatologist might be necessary.


Oclacitinib (Apoquel)
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This is a new medication best used for itch relief and blocking itch symptoms. It is popular, as it works fast. It does not address the inflammation in the skin; it just stops the itch sensation. This means that infection still needs to be controlled. 

Canine Atopic Dermatitis Immunotherapeutic (Cytopoint®) Injections 
Image result for cytopoint
This is a new treatment that uses vaccine technology to eliminate one of the main mediators of itch sensation. The injections provide relief from itching for 1 month in 80 percent of dogs and show effectiveness usually within 24 hours of the injection. For many dogs, relief of itch stops the vicious cycle of itch/infection. Again, any infections still need treatment, but the sensation of itch is usually controlled. For more details, visit cytopoint4dogs.com.

Atopic dermatitis is commonly seen in canines in the allergy season, and it is important to get your canine evaluated if the hallmark clinical signs are seen and to keep them controlled year round with one of these therapies.
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