Atopic Dermatitis - May 2020

The topic of the month concerns allergies, which can present in many ways, and be caused by many things. The term “atopic dermatitis” is a general name for an allergic skin disease due to environmental allergens. This type of disease can be mild to severe, and be seasonal or all year-round. Seasonal allergies have been flaring up this spring, seemingly more than ever in dogs, and less so in cats. The end results of allergies in animals can be very frustrating for owners, and extremely bothersome for the pets, even with treatment. I will go over the possible causes, possible diagnostic tests, and potential treatments for this condition.

Atopic dermatitis can develop in dogs and cats ranging from 3 months to 7 years of age, although it usually starts between 1-3 years old. There are many breeds that be pre-disposed to this disease, since it is has a strong genetic component. There is variability in geographic areas due to different allergens in those places. It can be seasonal or non-seasonal, depending on the animal. Unfortunately, many of the seasonal conditions may progress to having skin problems all year-round.

Disorders that are linked with atopic dermatitis are flea allergy, and concurrent cutaneous food reactions. Secondary infections on the skin due to bacterial or yeast overgrowth are common. Ear infections, and conjunctivitis (Pink Eye), are common as well. Rarely, nasal congestion, and anal sac infections can present due to allergies.

The signs of allergies can be varied. The most common sign is itching, which can be seen as licking, scratching, chewing, or rubbing. It can be at a local area, general scratching at the body, or present only in the ears as an infection or inflammation. Dogs or cats often have self-trauma to parts of the skin, lack hair in a certain area or have a generalized fur loss. Redness in skin is often seen as well. Staining of fur at areas of the body can be seen, most often on the paws, due to saliva staining from licking or chewing.

The diagnosis of atopic dermatitis can be made after all other reasons for skin disease are ruled out. Fleas can cause skin disease, and it looks look all other skin disease! They must be ruled out first, because they are easily treated. When all other potential causes are ruled out (other parasites, bacterial infections, fungal infections, or cancer (rarely)), then atopic dermatitis is the diagnosis, and depending on the circumstances, further diagnostics may be performed.

Allergy testing can be performed on pets, and is done usually at a veterinary dermatologist. Two types can be performed, blood testing, or intradermal test (testing the skin with many types of allergens directly). The intradermal test is considered the “gold standard” of allergy testing, and generally more accurate in detecting positive reactions to allergens. Ideally, testing for allergen response is to have both serology and intradermal tests performed and to have the most information, in order to best plan treatment. This is rarely done due to expense, and practicality. The unfortunate reality is that even when allergy tests are performed, and specific allergens are found to react in a dog or cat, often there is no “cure” and managing the skin conditions can be expensive, time-consuming, and life-long for that animal.

What are the treatments? There are many, and much of the time, several may be needed to effectively manage the skin disease. The ideal treatment is allergen-specific therapy, or allergen avoidance. With allergen-specific therapy, a vaccine made up with the most prevalent allergens to build up a tolerance in the body’s immune system so the reaction in the skin is lessened, or ideally, non-existent. If practical, this can be the most effective therapy for atopic dermatitis. Drawbacks are expense, the number of injections involved, and maintenance can be life-long. Allergen avoidance can work if the allergens can be removed from an environment, but often allergens are too ubiquitous in amount or types to be avoided. Antihistamines in dogs and cats, unfortunately in 70% or more cases, are ineffective at treating symptoms of skin disease. Antihistamines are best used as a multi-modal approach to treating atopic dermatitis. Omega 3 and 6 fatty acids are used a supplement in food, or included in food to help decrease inflammation in many parts of the body, including skin. Topical treatment can be very effective as well, such as medicated baths, or ointment for specific areas of the body.

Fortunately, there have been two types of therapies for dogs in treating skin disease introduced in the last 5 years that do not require additional diagnostics for allergens, and can be very effective when used as a monotherapy for skin disease. Apoquel (drug name Oclactinib) and Cytopoint are both therapies that work in different ways in the body’s immune systems to reduce or eliminate the signs of the atopic dermatitis. They are administered differently, Apoquel is a tablet given daily, and Cytopoint is given as an injection every 4-8 weeks, depending on severity and duration of symptoms. Drawbacks are that that medication can be expensive, and if the allergies are all year-round, the cost adds up. These treatments are specific for dogs, and not used in cats in treating atopic dermatitis.

The last topic is the use of steroids in treating skin disease in dogs and cats. They are very effective because they are a powerful anti-inflammatory drug. Unfortunately, there are many potential side effects to these drugs that can make using them less favorable and potentially make some conditions worse. If used long-term, side effects or complications are more prevalent because these drugs affect many organ systems, lower immune system effectiveness, and also can delay healing of skin issues. If used with the right cases, they are effective, but must be used sparingly, and short-term. They do not treat skin infections, and if used when there is a skin infection without the use of antibiotics, can make the infection worse.

In conclusion, skin allergies can be complex and potentially frustrating, especially if seen as a chronic condition. There are many ways to treat, and signs may need to be treated with multiple therapies. If you think your pet has signs of skin disease, please ask about it at your next visit, or give us a call. Enjoy your spring!

Dr. Jaime Kozelka
St. Francis Hospital for Animals