Canine Allergy - Atopy

Posted by Karen Egert on


This post concludes our series on allergies with Atopy or inhalant allergies.  After Flea Allergy Dermatitis, Atopy is the second most common cause of skin allergies in dogs.  Atopy occurs when your pet comes into contact with allergens in the environment.  It also tends to occur seasonally.  Unfortunately, management of this type of allergy can be difficult and usually requires lifelong therapy. 

Causes
When your dog comes into contact with an allergen, the dog's immune system will overreact.  This will result in itchiness which can be localized or over the entire body.  Common allergens can include:

  • grass and weed pollens,
  • tree pollens,
  • molds,
  • mildew
  • and dust mites.

Many of these allergies occur seasonally just like in humans.  It is also a genetically inherited disease seen most commonly in  Fox Terriers, Poodles, Dalmatians and West Highland Terriers.  However, all breeds of dogs can suffer from atopy.

Symptoms
The symptoms of atopy usually begin relatively early in life, many times as early as one year, and start out as seasonal.  Most dogs will show signs in the summer when airborne allergens are in higher concentrations.  As an atopic dog gets older they tend to become allergic to more substances and their symptoms tend to become less seasonal as well. Eventually, their itchiness can occur year-round.

Dogs with atopy are usually itchy, particularly the feet.  The skin may be red and irritated due to scratching, and the ears may also be inflamed. About half of all allergic dogs suffer from ear infections and this may be the only symptom.  The symptoms of food allergy are difficult to distinguish from those of atopy.  Signs to look for are:

  • Chewing or licking of their paws (Saliva will turn a light colored fur a reddish brown color)
  • Scratching the muzzle or rubbing it on the ground or with the paws
  • Scratching the ears
  • Shaking the head

Diagnosing Allergies
Laboratory tests can help in the diagnosis of allergies. Some allergy tests look at the blood serum, the part of the blood that has no red blood cells.  High levels of Immunoglobulin E suggests your pet is allergic or has a parasitic infection that is causing an allergy-like response.

Another serum test - radioallergosorbent serum test or RAST - identifies a reaction to specific antigens, like fleas and pollens. Interpreting the RAST test is difficult because there is no direct correlation between what your pet’s blood reacts to and the degree to which your pet exhibits symptoms. This is because allergies are caused by a complex interaction of many factors, not just the antibodies your pet makes that can be measured in a test.

Another clinical test for allergies is the intradermal skin test. With skin testing, small amounts of the possible allergen are injected into a shaved area of the skin. If your pet has a reaction with increased blood flow and histamine release, there will be a spot of red, raised, puffy skin around the injection site. As with the RAST test, there is no clear correlation between skin test results and your pet’s reaction to the material in everyday life. These tests are used as indicators of what your pet should avoid, but not as definitive diagnoses.

Treatment 
Treatment depends on the severity of the problem and the length of the dog’s allergy season. Avoiding the allergen is the most effective, however, this is often impossible. Treatment includes:

  • anti-inflammatory drugs like cortisone and anti-histamines,
  • antibiotics or antifungals for skin infections,
  • shampoos which can be anti-bacterial, anti-fungal or soothing and
  • hyposensitization.  Hyposensitisation is an injection of a small amount of the allergen after it has been identified.  This "reprograms" the dog's immune system so they become less sensitive over time. 

It is also very important for any dog with atopy to be on a year-round, comprehensive flea control program as these dogs tend to be more sensitive to the bites of fleas as well.

Your Vet will be the best person to determine both the type of allergy and treatment for your pet.


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