What is a Dog Allergy Test? Does My Dog Need One?

Allergies are common in dogs, who can react to numerous triggers such as fleas, food ingredients, and environmental allergens. However, determining the direct cause of these allergies can be difficult. 

You may have heard of dog allergy testing, which makes the process sound easy: Simply run an allergy test and find out the cause of your pup’s reaction.  Unfortunately, though, it’s not that straightforward. 

Why do dogs need allergy testing?

Veterinarians perform allergy testing after confidently diagnosing a dog with atopic dermatitis, a skin disorder caused by a hypersensitivity to commonplace and otherwise harmless environmental substances, such as plant pollens, dust mites, pet dander, and mold spores. Signs include excessive itching, especially on the paws, face, and hind end, hair loss, skin thickening and reddening, and recurrent skin and ear infections. To diagnose atopic dermatitis, a veterinarian must first rule out other potential causes, such as flea bite dermatitis, sarcoptic mange, primary skin or ear infections, food allergies, and cutaneous lymphoma. 

Once they make the diagnosis, the veterinarian can perform allergy testing to learn which allergens to include in allergen-specific immunotherapy (ASIT) (i.e., allergy shots). A vet can perform allergy testing using an intradermal skin procedure or blood testing. 

Intradermal Skin Testing

A veterinary dermatologist, or a veterinarian who performs the test frequently and stores an appropriate allergen collection, typically performs intradermal skin testing (IDST) on dogs. The procedure involves the following:

• Withholding medications — Medications, such as antihistamines and steroids, can interfere with IDST, and must be stopped before testing. 
• Identifying important allergens — Numerous allergens are available, and your veterinarian will determine the ones to use based on your dog’s geographic location and the season when your dog experiences signs. Most tests include about 50 allergens.
• Preparing your dog — Veterinarians sedate most dogs for this procedure. The veterinarian shaves an area on your dog’s chest behind their elbow and uses a permanent marker to mark the injection sites in a grid pattern.
• Injecting the allergens — The veterinarian injects a small amount of diluted allergen into the skin at each location.
• Interpreting the results — Reactions typically occur in 15 to 20 minutes. The sites are evaluated for redness, swelling size, and rigidity and graded on a zero to 4+ scale.
• Creating the ASIT — The allergens that create the strongest reactions are used to make the ASIT.

Blood Testing

Immunoglobulin E (IgE) produced by the immune system plays a significant role in allergic reactions. Allergy blood testing, known as a radioallergosorbent test (RAST), measures allergen-specific IgE levels in your dog’s blood. Any veterinarian can draw your dog’s blood and send the sample to a suitable laboratory that will test the blood for IgE antibodies against different environmental allergens. Substances that generate the highest IgE levels are selected for the ASIT.

Which allergy tests for dogs is better?

The preferred test is highly controversial, and many dermatologists perform both tests to choose the allergens to include in the ASIT. The following are the pros and cons of each test.

IDST Pros

• IDST has historically been considered the gold standard for allergy testing in dogs.
• The veterinarian and client receive same-day results.
• IDST allows the veterinarian to choose which allergens to test.

IDST Cons

• Many manufacturers provide test kits and allergens, but they lack standardization (i.e., the results depend on the veterinarian’s technique and interpretation).
• Veterinarians must sedate dogs and clip their fur.
• Existing skin disease may interfere with testing.
• Dogs must stop anti-allergy medications for up to several weeks to prevent drug interference.
• Rarely, dogs can have a significant adverse reaction.

RAST Pros

• Testing is standardized and objective.
• The test requires only a simple blood draw.
• Existing skin disease does not interfere with the test.
• Anti-allergic medications do not typically have to be stopped before testing.
• RAST is less expensive than IDST.

RAST Cons

• Historically, RAST testing has been associated with more false positive results.
• You may have to wait up to two weeks to receive RAST results.

Do at-home allergy testing kits for dogs work?

Veterinary-performed allergy testing can be expensive, and numerous at-home, more affordable allergy testing kits are available online. These tests proclaim they can test your pet’s hair or saliva and comprehensively report the environmental and food allergens that cause your pet to react. While these companies offer dog owners’ testimonials about their pup’s improvement, no peer-reviewed, published studies support their claims. The results also cannot be used to develop ASIT, which is why veterinarians perform allergy testing. In addition, studies¹ have proven that these tests are inaccurate when diagnosing food allergies. Elimination diet trials² are the only reliable way to determine the ingredient causing the reaction of dogs with food allergies. 

Diagnosing and treating a dog with allergies can be frustrating and expensive, but your veterinarian can best determine a successful management plan for your pup. Performing at-home allergy testing is likely a waste of money and can interfere with a reliable veterinary-directed diagnosis. If your dog has itchy skin, contact your veterinarian, and ensure they receive the appropriate care to help relieve their distress. 

Can allergy testing diagnose food allergies? 

Dogs can develop sensitivities to specific food ingredients, which can lead to skin issues as well as chronic diarrhea and vomiting. Although food antigens can be included on blood allergy testing, the most accurate way to reach a food allergy diagnosis is by following a veterinarian-recommended food trial. During a food trial, a dog is fed a diet formulated with novel protein and carbohydrate sources the dog has likely never been exposed to, or a diet containing hydrolyzed proteins the dog’s immune system will not recognize. If the dog’s symptoms improve during the 8 to 12-week trial, food allergies are likely. Once the specific ingredients a dog is sensitive to are identified, the owner can feed a diet that does not contain those ingredients. Ollie offers a variety of fresh and baked diets made with high-quality protein and carbohydrate sources that can be beneficial for dogs with food allergies.

Does my dog need an allergy test?

Allergies are a common issue in dogs, which makes allergy testing a valuable diagnostic tool. Your dog may benefit from allergy testing if they have the following signs:

• Frequent itching and scratching
• Licking their feet
• Biting their skin
• Red, irritated, or flaky skin skin
• Hair loss
• Chronic ear infections

Dogs with allergies may have seasonal signs, often in the spring and summer when pollens, grasses, and other natural antigens are most abundant. However, some dogs are sensitive to indoor antigens, such as dust mites or food ingredients, and will have year-round signs. If you believe your dog may suffer from allergies, ask your veterinarian whether an allergy test can help them reach an accurate diagnosis.

Sources:

1. https://pubmed.ncbi.nlm.nih.gov/31517577/ 
2. https://pubmed.ncbi.nlm.nih.gov/30819419/