Atopic Dermatitis (AD) is second only to flea allergies as the most common cause of itching in dogs. While new preventative products have made controlling flea infestations relatively easy for owners, the same cannot always be said about the management of atopic dermatitis. To deal with this frustrating condition, owners first need to understand the terminology surrounding it.
- atopy n. a genetic tendency toward allergic reactions that often cause itchy skin
- dermatitis n. inflammation of the skin
- allergy n. an abnormal reaction of the body's immune system to substances that often do not incite a similar reaction in other individuals
Therefore, atopic dermatitis is inflammation of the skin that is caused by a genetic tendency toward abnormal immune reactions. In AD, the triggers for these reactions are often compounds associated with pollens, molds, insects, mites, and the dander of other animals that are absorbed through the skin. Once inside the body, the immune system of an allergic dog reacts with a cascade of antibodies, white blood cells, and other physiologic reactions that result in skin inflammation and itching.
Atopic Dermatitis Symptoms
Most dogs suffering from allergies develop some combination of the following clinical signs:
- Red skin
- Loss of fur
- Small pus filled or solid bumps in the skin
- Sores that might ooze
- Recurrent skin and ear infections
Typically, symptoms first develop when a dog is between six months and three years of age and are focused around the face, ears, paws, lower legs, armpits, or belly, but this is not true for every dog that is diagnosed with atopic dermatitis.
AD is a diagnosis of exclusion, meaning that no single test is available that can definitively diagnose the condition. Other common causes of itching and skin inflammation must be ruled out through a detailed history, physical examination, and lab work. Depending on a dog's presentation, a veterinarian might need to run:
- a fungal culture to rule out ringworm
- skin scrapings to look for mange mites (e.g., Demodex and Sarcoptes)
- skin cytology to check for bacterial or yeast infections
- dietary elimination trials to diagnose food allergies
- fecal exams or prophylactic deworming to rule out intestinal parasites that can cause skin inflammation and itching
- skin biopsies
Managing Canine Atopic Dermatitis
"Atopic Dermatitis (AD) is second only to flea allergies as the most common cause of itching in dogs."
The symptoms of skin inflammation and itching associated with allergies are brought about by many different physiological processes in the body. Therefore, effective treatment usually involves combining several of different treatment modalities available. Options include:
Antihistamines (e.g., diphenhydramine or cetrizine) can help with mild allergic symptoms.
Glucocorticoids (e.g., prednisone) are very effective at relieving inflammation and itching in dogs. They can be given orally, by injection, and/or applied topically. Ideally, glucocorticoids should only be used for a short period of time because extended use is associated with serious side effects like increased risk of infection, hyperadreoncorticism, decreased wound healing, and more. To reduce the health risks associated with the long term use of glucocorticoids, it is important to find the lowest dose that is effective when given no more frequently than every other day.
Cyclosporine (e.g., Atopica) is also very effective at reducing the inflammation and itching associated with atopic dermatitis. This immunosuppressive drug is more expensive than are glucocorticoids but is generally safer to use over an extended period of time.
Tacrolimus is another immunosuppressive drug that is sometimes prescribed for dogs that don't respond to traditional treatments for atopic dermatitis.
Desensitization (e.g., allergy shots or oral solutions) can help make dogs less sensitive to the allergens that trigger their symptoms. Once a veterinarian is fairly sure that atopic dermatitis is at least partly responsible for a patient's symptoms, intradermal skin tests or blood tests can help determine what a dog is allergic to and those allergens are then included in a solution used to desensitize the patient. Sixty to seventy percent of owners report a greater than 50% improvement in their dog's allergy symptoms with desensitization therapy, but dogs do require lifelong treatment to keep their symptoms under control.
Bathing helps to remove allergens that collect on the surface of the skin and in the fur. Some shampoos and rinses also contain medications to help with itching, inflammation, and skin infections.
Antibiotics and/or antifungal medications may be given systemically and/or topically when dogs with atopic dermatitis develop secondary skin infections.
Essential fatty acids given orally and/or topically (e.g., fish oil supplements and products like Dermoscent) can help improve the skin's natural ability to act as a barrier to allergens.
Effective flea preventatives are essential for dogs with atopic dermatitis because many of these individuals are also allergic to flea bites.
Prognosis for Atopic Dermatitis
Atopic dermatitis is a chronic disease that cannot be cured, but can usually be managed well enough to keep dogs comfortable and healthy. Cooperation and communication between a dedicated owner and a knowledgeable veterinarian is essential for dealing with the allergic flare ups that inevitably occur over the pet's lifetime.
Close monitoring is also very important, especially when a dog receives immunosuppressive drugs over a long period of time. Many veterinarians recommend that blood work and a urinalysis be run every six to twelve months to ensure that these powerful medications are not adversely affecting the body and that infections are not going undiagnosed.
Specific management of canine and feline atopic dermatitis. Wilson L. Wild West Veterinary Conference. October 17-21, 2012. Reno, NV.
Dictionary of Veterinary Terms: Vet-speak Deciphered for the Non-Veterinarian. Coates J. Alpine Publications. 2007.
Interventions for atopic dermatitis in dogs: a systematic review of randomized controlled trials. Olivry T, Foster AP, Mueller RS, McEwan NA, Chesney C, Williams HC. Vet Dermatol. 2010 Feb;21(1):4-22.
Cushing's Disease. Washington State University College of Veterinary Medicine. Accessed 10/19/12.
A systematic review and meta-analysis of the efficacy and safety of cyclosporine for the treatment of atopic dermatitis in dogs. Steffan J, Favrot C, Mueller R. Vet Dermatol. 2006 Feb;17(1):3-16.
Is the skin barrier abnormal in dogs with atopic dermatitis? Olivry T. Vet Immunol Immunopathol. 2011 Nov 15;144(1-2):11-6.
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