How to Diagnose Canine Allergies

Two Parts:Identifying AllergiesGetting a Veterinary Diagnosis

Allergies are relatively common in dogs, with an estimated 10-15 % of dogs affected by them in some form.[1] Allergic reactions are caused by the immune system overreacting to a substance that it is sensitive to. The job of the immune system is to protect the body against infection but, in the case of an allergy, its response is disproportionate, inappropriate, and can cause harm.[2] If you have a dog, be on the look out for the signs of allergies and take your dog to the veterinarian if you think that your dog's potential allergies are negatively affecting its life.

Part 1
Identifying Allergies

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    Look for symptoms of an allergy. There are a range of possible symptoms that could result from an allergy. However, none of these signs are "specific," which means none of them are enough in their own right to make a diagnosis. For example, for a dog with diarrhea this could be the result of a dietary allergy, an infection, parasites, garbage gut, lymphoma, or any one of a number of other causes. However, common symptoms of an allergy include:
    • Itchiness: This symptom becomes evident if your dog is scratching or chewing, pulling fur out, rubbing its face or bottom along the ground, or excessively licking itself.
    • Poor skin and coat: Your dog may have patchy hair loss, red inflamed skin, or spots and rashes.
    • Ear infections: Repeated ear infections can be a sign of allergies.
    • Redness: Inflamed skin and rashes can be a symptom of allergies.
    • Gastrointestinal signs: Vomiting, diarrhea, excessive flatulence, and weight loss can be signs that your dog is allergic to something it is ingesting.
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    Suspect allergies especially in young dogs. Allergies typically develop in young dogs, although it is unusual to see signs in pups younger than six months because they haven't been exposed to an allergen enough times for the immune system to overreact. Typically, once a dog has developed symptoms of an allergic reaction, each time it encounters the allergen his symptoms get worse. [3]
    • This accounts for why dogs with seasonal allergies to pollens often seem to get worse from year to year.
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    Look for possible allergens that your dog has been repeatedly exposed to. It is a common misunderstanding that a pet newly exposed to an allergen for the very first time will have an allergic reaction. In truth, an allergic reaction occurs after the dog has been repeatedly exposed to the allergen, which primes up the immune system for overreaction. [4]
    • Thus, for a dog allergic to food it's not the first time they eat the item that their allergies flare up, but it's after repeated exposure.
    • It is, however, true that allergic reactions get worse with time and repeated exposure.
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    Consider possible allergens the enter the body in a variety of ways. Allergens can trigger allergic reactions by entering the body in different ways. Perhaps the easiest allergy to understand is a contact allergy. This is where the dog lies on a substance to which they are sensitive, and the direct contact of the allergen against the skin triggers the reaction. Typically, the allergy is localized, meaning that the inflammation flares up in the spot where the skin contacted the allergen.
    • Food allergies are fairly self-explanatory in that there is a food which the dog eats and then reacts to. However, the dog's body can react in different ways. Some dogs develop inflammation and irritation of the gut lining, which causes gastrointestinal signs such as vomiting or diarrhea, or the allergy may show itself as inflamed skin and itchiness.
    • A common allergy is to air-borne allergens, such as tree, grass, or flower pollen. These contact the skin directly or are inhaled to set up an inflammatory reaction.[5]
    • Inhaled allergens, such as pollens or mold spores, often cause skin itchiness. Dietary allergens, such as beef or wheat, can also cause itchiness or upset stomachs.[6]
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    Make sure your dog is free of parasites. Many dogs are allergic to fleas and this is a relatively easy allergy to treat. Just make sure that you are giving your dog a flea medication on a regular basis, as once the fleas are gone, the allergy will be as well.[7]
    • Aside from allergies, it is important to always have your dog treated for fleas and ticks. It is especially important for dogs that spend a lot of time outdoors, in wooded areas.

Part 2
Getting a Veterinary Diagnosis

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    Take your dog to the veterinarian. Diagnosing allergies is notoriously difficult. Although there are several tests available, each has advantages and disadvantages. Most clinicians take an overall approach, in which they eliminate possible causes, such as parasites, and interpret the test results in the light of the dog's history, symptoms, and response to treatment.[8]
    • The vet first performs a clinical examination looking at the skin, but also feeling the abdomen and listening to the chest. He or she then examines the coat in more detail looking for signs of parasitic infection, such as flea droppings or patchy hair loss, which could indicate mange.
    • The vet may wish to rule out parasites in the itchy dog, before proceeding to more extensive and expensive tests. This may be simply a case of using an effective insecticidal product in order to kill any parasites present.
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    Discuss further testing with your veterinarian. Once the preliminary testing is done, the vet has different options for a more specific diagnosis. These include blood tests, skin tests, skin biopsy, and dietary trials. These can give you a more specific diagnosis but there is no guarantee that they will actually figure out the root of the problem.
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    Consider paying for blood tests. The big advantage of blood tests is their convenience. The clinician draws a sample of blood and sends it to the lab for analysis. However, blood tests are costly and can give unreliable results.
    • The theory behind blood testing for allergies is that the body produces immunities called IgE when it encounters an allergen. Theoretically, the higher the level of IgE to an individual allergen, the more allergic the dog is. This sounds simple, but these tests are known to come up with false positive results. This means the results cannot always be relied upon to be 100% accurate.[9]
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    Discuss the option of doing skin tests on your dog. You may be familiar with intradermal tests, as they are commonly used on people. The test involves clipping an area of fur, dividing the skin into a grid, and then injecting a small bit of allergen into the skin. The skin then may produce a reaction in response, which is a raised blister like bump.[10] The larger the reaction, the more allergic the dog to that particular allergen.
    • Intradermal skin tests are considered the gold standard for allergy tests, but even they can be problematic. Some dogs require sedation in order to have the test run, as the repeated pin pricks can be uncomfortable. However, some sedatives can inadvertently interfere with the allergic reaction and suppress the positive to make a false negative.
    • Also, intradermal skin tests are expensive because the samples of allergens don't keep for long and unless the clinician does a lot of testing, there is a lot of waste. This can mean referral to a skin specialist who does have the caseload to warrant keeping in house test kits.
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    Talk with your veterinarian about the option of a skin biopsy. The role of skin biopsy in diagnosing allergic disease is limited. The sample under a microscope only suggests general inflammation that occurs with allergy, but cannot make a definitive diagnosis. Skin biopsies can, however, rule out other problems that mimic allergies, such a pemphigus or certain infections.[11]
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    Consider dietary trials. These are reserved for suspected food allergies or to rule out food allergy. While lab tests do exist for food allergy, again the results are largely unreliable and it is best to run a dietary trial.[12] A food trial consists of feeding the dog foods it has never previously encountered, and nothing else, for a period of 8 -12 weeks.
    • The theory is that this gives allergens time to clear from the system. If the dog's symptoms resolve in this time then it was likely an allergy that was responsible for them.
    • However, dietary trials take tremendous commitment on the part of the owner, since the dog must eat an extremely restricted diet. Even a single illicit treat fed during the trial period could undo all the good work.[13] If your dog is a scavenger or you live with people who will feed the dog treats behind your back, then a dietary trial can be extremely challenging.
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    Put your dog on an anti-inflammatory medication. All in all, allergies can be difficult to pinpoint. This is why broad-acting medications, such as anti-inflammatories, are a popular solution to allergy problems. If your veterinarian is sure your dog has an allergy, he or she may then prescribe anti-inflammatory drugs to reduce the itch and inflammation that is causing the dog (and owner) such distress.
    • The vast majority of allergy problems in dogs are diagnosed up to the point that the clinician is sure an allergy is responsible, however not to the point of labeling exactly what the dog reacts to.

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Categories: Canine Health