Atopic Dermatitis
By Dr. Tyler Charbonneau
Residency-trained, Dermatology
www.pvesc.com
Atopic dermatitis is the term used in veterinary medicine for a disease condition thought to be related to allergies to environmental substances. These substances, called “allergens”, may include plant pollens, house dust mites, or mold spores. Most allergic patients begin to show symptoms between one and three years of age, and it is common to see the allergic signs worsen in severity and length of time. These symptoms may include scratching, paw licking, and ear and skin infections including “hot spots.” Due to the hereditary nature of the disease, several breeds of dogs appear predisposed to allergies. These dog breeds include Golden Retrievers, Labrador Retrievers, West Highland White Terriers and other terriers, and Bulldogs. However, any dog or cat breed including mixed breeds can have atopic dermatitis.
Allergy testing may be utilized to determine what your pet is allergic to in the environment. There are two types of allergy tests available: the intradermal allergy test and blood/serum test (serologic allergy testing). In an intradermal allergy test, the coat is clipped on one side of the chest and small amounts of common allergens are injected into the skin. After 10 to 15 minutes the skin is observed for reactions to the allergens. An intradermal allergy test is considered the testing of choice as it has the potential for fewer false positives and is usually more comprehensive. The disadvantages include the need for sedation and the discontinuation of certain drugs such as antihistamines and steroids prior to testing.
In a blood allergy test, a blood sample is obtained and sent to a laboratory. At the laboratory, the protein levels (antibodies) to the allergens are measured. Results are usually available within 2 weeks. The advantages of blood allergy testing are that patients do not need to be sedated for the test and certain drugs such as antihistamines and steroids do not need to be stopped. The disadvantages of blood allergy testing are a higher possibility of false positive results and variable sensitivity and specificity among various laboratories.
Treatment
If a dog is diagnosed with atopic dermatitis, there are three main methods of therapy.
• Avoiding allergens: It is usually not possible 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, cyclosporine (Atopica), and newer drugs such as oclacitinib (Apoquel) and lokivetmab (CytoPoint). Some dogs develop side-effects from taking certain anti-itch medications, such as steroids. Different anti-allergy medications may need to be tried as not every medication works in all pets. Your veterinarian will discuss which medications are most appropriate for your pet based on symptoms and severity and discuss potential side effect associated with each drug. Keeping a diary to document your pet’s level of itching and response to various treatments will be helpful.
• Allergen specific immunotherapy: Immunotherapy involves giving a series of diluted allergens based on what your dog is allergic to. These diluted allergens may be given in the form of an allergy injection under the skin or as an oral drop in the mouth. Allergen-specific immunotherapy makes pets less sensitive to their allergens and 60-80% of patients improve on immunotherapy. However, improvement on immunotherapy takes time and may require months to become effective. When helpful in reducing allergic symptoms, immunotherapy is usually continued life-long but can be given less frequently over time.
Lastly, topical therapy and prevention of potential itch triggers are important to keep atopic dermatitis under control. It is helpful for dogs with numerous pollen allergies to remain indoors when pollen counts are very high to reduce exposure. Bathing and foot-wipes can also be very helpful after walks. If you believe your pet may be experiencing a bacterial or yeast infection, please call your veterinarian as these conditions can greatly exacerbate itching. Frequent baths, fatty acid administration (either added to the diet or as fish oil capsules) can also help improve the skin barrier to prevent allergens from penetrating the skin. Keep pets on flea control year-round as ectoparasites are often triggers of itching as well.
Helpful websites:
www.pollen.com Helpful website that records daily pollen counts.
www.itchcycle.com Great website about atopic dermatitis with handouts and videos.
www.pollenlibrary.com Pollen library to research various allergenic plants and molds.