Diagnosing Dog Allergies with a RAST Test

Dogs may suffer from different allergies induced by environmental factors, food or parasites. The RAST test is a good allergy test to diagnose inhalant dermatitis that's caused by pollen, dust or mold. The RAST test (radioallergosorbent) is not conclusive for contact allergies.

Symptoms of Canine Allergies

Canine allergies include symptoms such as:

  • Skin itchiness
  • Redness
  • Swelling
  • Sneezing
  • Licking of feet or affected areas
  • Chewing and biting the itchy areas

Allergies in dogs may be caused by environmental factors, ingredients in food or parasites such as fleas or mites.

If the dog touches plants or materials he is allergic to, he may develop contact allergies.
Allergy Tests

Types of allergy tests include:

  • Blood testing; a blood sample is needed
  • Intradermal skin testing; antigens are injected and the skin gets irritated if the dog is allergic to that substance

In a blood test, vets look for antigen-induced antibodies that may exist in the dog's body. Blood testing may be of 2 types:

  • The RAST test (radioallergosorbent)
  • The ELISA test (enzyme linked immunoabsorbent assay)

The Radioallergosorbent Test (RAST)

For the RAST test, a blood sample is taken. The blood will be checked for a negative reaction to different allergens such as mold, pollens or chemicals.

The blood may also be tested for allergens such as food, or contact allergies to nylon and synthetic materials, but the results may not be accurate.

Being a complex analysis, the RAST testing takes about 2 weeks.

The test may have some shortcomings. Being designed for humans, the test may result in false negatives for dogs. Therefore, it may indicate a false allergy in your pet. This is why vets recommend supplementary intradermal skin testing (IDST).

The IDST is performed by injecting allergens under the dog's skin and observing the reactions. If the dog presents redness, this means he is allergic to the injected allergen. The IDST shows about 75% accuracy in identifying allergies. However, dogs that are under treatment with steroids or antihistamines will not show conclusive results.

The ELISA test is similar to the RAST test, and most vets agree that it gives more accurate results.

Treatment for Canine Allergies

Once the allergens are discovered, you need to limit the dog's exposure to them, if possible. Allergic reactions can be minimized with antihistamines, corticosteroids or allergy shots (immunotherapy).

If the allergies are caused by parasites or fungi, these must be removed and precautionary measures should be taken.

A change in diet is needed to reduce the allergic reactions. Fatty acid supplements are recommended for allergic dogs.

Before allergy testing is performed, the dog needs to be tested for other medical conditions, to rule out any other diseases that may cause the same symptoms. For example, a dog with thyroid problems may display similar symptoms to allergies.

Allergy testing using the RAST test may give a proper diagnosis in identifying the allergens. Once the allergens are identified, an effective treatment can be prescribed.