Allergy testing in dogs helps to identify specific allergens that might be causing an allergic reaction, primarily for environmental allergies (atopy). This information can then be used to guide treatment, especially immunotherapy (allergy shots or drops).
Signs Your Dog Might Have Allergies
Before considering testing, it’s important to recognize the common signs of canine allergies:
Itching (Pruritus): Excessive scratching, licking, or biting, especially of paws, flanks, ears, and groin.
Skin Issues: Redness, rashes, hot spots, scabs, hair loss, thickened skin (lichenification).
Ear Infections: Recurring ear infections (bacterial or yeast), often with a foul odor.
Foot Problems: Licking and chewing paws, sometimes leading to inflamed, red, or discolored feet.
Respiratory Symptoms: Less common, but can include sneezing, nasal discharge, or reverse sneezing (more common with environmental allergens).
Gastrointestinal Upset: Vomiting, diarrhea, or frequent bowel movements (more common with food allergies).
Why Perform Allergy Testing?
Pinpoint Allergens: Identify the specific substances (e.g., pollens, dust mites, molds) your dog is reacting to.
Guide Immunotherapy: The primary reason for testing environmental allergies is to formulate a custom-made allergy vaccine (immunotherapy) for your dog, which can desensitize them to their triggers.
Rule Out Other Conditions: While not a diagnostic tool for other diseases, testing can help confirm allergies as the root cause of symptoms after other conditions (like parasitic infestations, bacterial/yeast infections) have been addressed or ruled out.
Aid in Avoidance: Knowing what your dog is allergic to can help you minimize their exposure to those allergens.
Types of Allergy Tests
There are two main types of allergy tests for dogs, primarily targeting environmental allergens (atopy):
Intradermal Skin Testing (IDST) / “Skin Prick Test”
Serum (Blood) Allergy Testing
For food allergies, the gold standard is an elimination diet trial, not usually a blood or skin test.
1. Intradermal Skin Testing (IDST)
How it Works: Considered the “gold standard” for diagnosing environmental allergies. Small amounts of common allergens (e.g., pollens, dust mites, molds, insect dander) are injected just under the skin.
Procedure:
Your dog will typically need sedation or light anesthesia to keep them still.
A patch of hair on their side is shaved.
A grid is marked on the skin, and tiny amounts of various allergens are injected into designated spots.
A control (saline) and a positive control (histamine) are also injected.
The veterinarian (usually a veterinary dermatologist) observes the injection sites after about 15-20 minutes for a “wheal and flare” reaction (a raised, red bump), similar to a mosquito bite. The size of the reaction indicates the degree of sensitivity.
Pros:
Considered the most accurate method for identifying environmental allergens.
Directly observes the immune response.
Results are immediate.
Provides results that are highly correlated with successful immunotherapy.
Cons:
Requires sedation or anesthesia.
Requires referral to a veterinary dermatologist (specialist).
Requires withdrawal of certain medications (antihistamines, steroids) for several weeks prior, which can be challenging if your dog is very itchy.
Can be more expensive than blood tests.
Not widely available everywhere.
2. Serum (Blood) Allergy Testing
How it Works: A blood sample is taken from your dog and sent to a specialized laboratory. The lab measures the levels of IgE antibodies (immunoglobulin E) in the blood that are specific to various environmental and sometimes food allergens. High levels of IgE suggest an allergic sensitivity.
Procedure:
A blood sample is drawn by your regular veterinarian.
The sample is shipped to a diagnostic laboratory.
Results are typically available within a few days to a couple of weeks.
Pros:
Less invasive; only requires a blood draw.
Does not usually require sedation.
Medication withdrawal periods may be shorter or not required, depending on the specific test and lab.
More readily available through general veterinary practices.
Often tests for a broader range of allergens.
Cons:
Considered less sensitive and specific than IDST by many dermatologists.
Can produce false positives (detects antibodies that don’t cause clinical signs) or false negatives.
Correlation between IgE levels and actual clinical allergy symptoms can vary.
Not reliable for diagnosing food allergies.
Results may not correlate as highly with immunotherapy success compared to IDST.
3. Food Elimination Diet Trial (for Suspected Food Allergies)
How it Works: This is the gold standard for diagnosing food allergies, which are reactions to specific proteins in a dog’s diet. Blood and skin tests for food allergies are generally considered unreliable.
Procedure:
Your dog is placed on a strict, novel protein diet (a protein source they’ve never eaten before, like kangaroo or duck) or a hydrolyzed protein diet (proteins broken down so small the immune system doesn’t recognize them).
This diet is fed exclusively for 8-12 weeks, with no other treats, chews, or human food.
If symptoms resolve, old food items are slowly reintroduced one by one (called a “challenge”). If symptoms return after reintroducing a specific food, that food is identified as an allergen.
Pros:
Most accurate method for diagnosing food allergies.
Non-invasive.
Cons:
Requires strict owner compliance for several weeks.
Can be challenging to find appropriate novel protein sources.
Time-consuming.
Preparing Your Dog for Allergy Testing (Especially IDST)
Medication Withdrawal: This is crucial.
Antihistamines: Must be stopped 1-2 weeks prior.
Oral Steroids: Must be stopped 4-8 weeks prior (dose-dependent).
Injectable Steroids: May require 2-3 months withdrawal.
Topical Steroids: Should be stopped in the area to be tested 1-2 weeks prior.
Immunosuppressants (e.g., Apoquel, Cyclosporine, Cytopoint): Withdrawal periods vary, often 4-8 weeks, depending on the drug and the dermatologist’s protocol.
Always consult your veterinarian or dermatologist for the exact withdrawal schedule.
Fasting: If sedation is required for IDST, your dog will need to fast for 8-12 hours prior.
Interpreting Results
A positive test result (wheal on IDST, high IgE on blood test) means your dog is sensitized to that allergen, but it doesn’t automatically mean it’s causing their clinical signs. The results must be correlated with your dog’s history, symptoms, and the season of their allergies.
A negative test result does not completely rule out allergies. There might be allergens not included in the panel, or the test might have missed a sensitivity.
For environmental allergies, the primary benefit of testing is to formulate immunotherapy. If you don’t intend to pursue immunotherapy, the value of testing might be limited to simply identifying potential triggers for avoidance (though complete avoidance is often impossible).
Limitations of Allergy Testing
False Positives/Negatives: Both IDST and serum tests can have them.
Doesn’t Test for Everything: Panels include common allergens, but your dog might be allergic to something not on the list.
Correlation with Clinical Signs: A positive test doesn’t always mean that allergen is causing disease. Conversely, a dog can have allergic symptoms without a strongly positive test.
Not a Cure: Testing identifies problems but doesn’t solve them; it’s a guide for treatment.
Not for Food Allergies (Blood Tests): As mentioned, blood tests for food allergies are generally unreliable.
What Happens After Testing? (Treatment Options)
If allergies are confirmed through testing or elimination diet, treatment options include:
Immunotherapy (Allergy Shots/Drops): The only treatment that targets the underlying cause of environmental allergies. A custom-made serum is given via injections or oral drops to desensitize your dog over time.
Medications:
Antihistamines: OTC (e.g., Benadryl, Zyrtec) may help mild cases.
Corticosteroids: Powerful anti-inflammatories, effective but with potential side effects for long-term use.
Apoquel (Oclacitinib): Targets the itch pathway, very effective for many dogs.
Cytopoint (Lokivetmab): An injectable antibody that targets key itch-producing proteins, providing weeks of relief.
Cyclosporine (Atopica): Immunosuppressant that can help manage severe allergies.
Environmental Control: Regular cleaning, air purifiers, frequent bathing (with medicated shampoos), flea control, avoiding known triggers.
Dietary Management: For diagnosed food allergies, strict adherence to a specific diet is key.
Cost Considerations
Allergy testing can be an investment.
Blood tests are generally less expensive than IDST.
IDST requires a specialist consultation, sedation, and the procedure itself.
Immunotherapy is an ongoing cost, but it can significantly reduce the need for other medications long-term.
Always consult with your veterinarian to discuss your dog’s specific symptoms, explore diagnostic options, and determine the best course of action for managing their allergies.
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