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Canine Atopic Dermatitis

Issue Description
Atopy is a common cause of chronic itching in dogs. (It is believed to affect 15% of dogs in North America.) Dogs that have atopy usually itch and so scratch a lot, which can cause red, moist, irritated skin. The face and feet are most commonly affected but ear infections are also common. Sometimes, dogs with atopy will also have runny eyes or nose.
Other Names
Atopy, Allergic Dermatitis, Allergic Inhalant Dermatitis


Causes
The most common allergens include airborne pollens such as grasses, trees, weeds, and fungal spores. Indoor allergens include natural fibers such as wool and household dust mites. In addition, some animals are allergic to the dander from other animals in the same dwelling. It commonly starts between the ages of one and five years.

Breeds Commonly Affected
  • Boston Terrier
  • Boxer
  • Cairn Terrier
  • Chinese Shar-Pei
  • Dalmation
  • English Setter
  • Golden Retriever
  • Irish Setter
  • Labrador Retriever
  • Lhasa Apso
  • Miniature Poodle
  • Miniature Schnauzer
  • Pug, Scottish Terrier
  • West Highland White Terrier
  • Wire-Haired Fox Terrier.


  • Symptoms
    Atopy is usually first seen when your pet is between 1-3 years of age, although it can develop as late as 6-7 years of age. Initially, symptoms may be seasonal, but usually progress to being present year-round with time.

    The primary symptom of atopy is itchiness. Your dog may scratch, lick, chew, or rub along the carpet. The face, paws, lower legs, and groin are the most commonly affected areas, followed by the ears and eyes. Initially, you may see slight reddening of the affected skin areas. Eventually, these areas are likely to develop more severe lesions and may become abraded, thickened and wrinkled in appearance. The area may also become darker in color (hyperpigmentation) or stained from constant licking (saliva stains). You are likely to notice hair loss as well.


    Diagnosis
    The veterinarian will ask the owner about the animal's history of symptoms. During the physical examination, the presence of itching and skin lesions will be assessed. Before concluding a diagnosis of inhalant allergy, the veterinarian will need to rule out other skin diseases including food hypersensitivity, flea allergy dermatitis, sarcoptic mange, contact dermatitis, and yeast infection of the skin. Diagnostic procedures can include bloodwork and urinalysis, and skin scrapings, and fungal cultures. Intradermal skin testing is believed to be the most accurate of the allergy tests; this procedure should be performed by an experienced veterinarian or by a veterinary dermatologist. There are also blood tests which may provide information about inhalant allergies for canines.

    Treatment
    Treatment involves the avoidance of identified allergens when possible. Essential fatty acid supplements, given at higher doses, can help control the symptoms. Medications can include antihistamines, corticosteroids, and immunotherapy, or allergy shots. Owners should be aware that long-term use of corticosteroids can result in complications including iatrogenic Cushing's disease, or excessive levels of glucocorticoids in the body, diabetes mellitus, and worsening bacterial or fungal skin infections. Allergy shots are formulated specifically for individual animals and are administered by an injection under the skin. Improvement of symptoms can take three to twelve months. Immunotherapy is successful in reducing itching in 60 to 70 percent of dogs and 73 percent of cats. In addition, shampoos and topical products may be beneficial.

    Prognosis
    Inhalant allergy is a life-long disease that tends to worsen with age. Therefore, treatment is required for the duration of the animal's life.

    Prevention
    Prevention includes avoiding known allergens by maintaining a dust-free house, closing windows, and keeping the animal indoors during high pollen season. It is also important to minimize complicating factors such as fleas, a dirty haircoat, and skin or ear infections. Because the predisposition to inhalant allergies may be genetically transmitted, affected animals should ideally not be bred.

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