Allergy Testing for Dogs: What It Can—and Can't—Tell You

"Should My Dog Be Allergy Tested?"

This is one of the first questions many owners ask after their dog is diagnosed with allergies.

It seems logical.

If your dog has allergies...

Wouldn't you want to know exactly what they're allergic to?

The answer is:

Yes—but not in the way most people think.

The biggest misunderstanding about allergy testing is believing that it tells us whether your dog has allergies.

It doesn't.

Instead, allergy testing is primarily used to determine which environmental allergens should be included in allergy immunotherapy ("allergy shots" or oral allergy drops).

The Biggest Myth About Allergy Testing

One of the most common misconceptions is:

"Let's do an allergy test and see if my dog has allergies."

Unfortunately...

That's not what allergy testing is designed to do.

There is no blood test or skin test that can diagnose environmental allergies by itself.

Dogs without clinical allergies can sometimes have positive allergy test results.

Dogs with significant allergies may react differently depending on the season, medications, and other factors.

This is why veterinarians diagnose allergies clinically—not by test results alone.

Before We Even Think About Allergy Testing

Before recommending allergy testing, your veterinarian should first rule out other causes of itching, including:

• Fleas
• Mites (mange)
• Skin infections
• Ear infections
• Food allergy
• Hormonal diseases
• Contact irritation
• Pain
• Behavioral licking

If these problems haven't been addressed first—including recurring skin infections and ear infections—allergy testing is unlikely to provide useful answers.

The Two Types of Allergy Testing

There are two primary methods used to identify environmental allergens.

Intradermal Skin Testing

This is considered the gold standard by many veterinary dermatologists.

Small amounts of common environmental allergens are injected just beneath the skin after a small area has been clipped.

The dermatologist then observes which allergens produce a localized reaction.

Skin testing directly evaluates how the skin responds to individual allergens and has been used successfully for decades.

Advantages

• Excellent clinical experience behind it.
• Considered the reference standard by many dermatologists.
• Helps develop individualized allergy immunotherapy.

Limitations

• Requires referral to a veterinary dermatologist.
• Sedation is often needed.
• Hair clipping is required.
• Some medications must be stopped beforehand because they can interfere with results.

Blood Allergy Testing (Serum IgE Testing)

Blood testing measures antibodies against environmental allergens.

A blood sample is collected and sent to a specialized laboratory.

Results help identify which environmental allergens may be contributing to your dog's atopic dermatitis.

Advantages

• Simple blood draw.
• No sedation.
• Convenient for many patients.
• Can often be performed by your primary care veterinarian.

Limitations

• Results must always be interpreted alongside your dog's clinical history.
• Different laboratories may produce somewhat different results.
• Positive results do not automatically mean an allergen is clinically important.

What About Mail-In Hair Tests?

You may have seen advertisements claiming they can identify your dog's allergies using:

• Hair
• Saliva
• Fur
• Specialized scanning devices

These tests can be appealing because they're convenient.

However, they have not been shown to accurately diagnose environmental or food allergies in dogs, and they are not recommended by veterinary dermatologists.

If you're considering one of these tests, talk with your veterinarian first so you understand what the results can—and cannot—tell you.

So Why Do We Test?

If allergy testing doesn't diagnose allergies...

Why do we do it?

The answer is simple.

To create allergen-specific immunotherapy.

In other words...

To build a customized allergy vaccine.

How Is Allergy Immunotherapy Developed?

Once your veterinarian or veterinary dermatologist has diagnosed environmental allergies and allergy testing has identified relevant environmental allergens, those results are used to formulate a customized immunotherapy treatment.

Depending on the program, this may be given as:

• Allergy injections
• Oral allergy drops

The goal isn't simply to control symptoms.

The goal is to gradually teach the immune system to become less reactive to those allergens over time.

Unlike medications that suppress itch, immunotherapy attempts to change the disease itself.

An Easy Way to Think About It

Imagine your dog's immune system has become overly suspicious.

Every time it sees pollen, it sounds the alarm.

Immunotherapy is like patiently retraining that immune system.

Instead of shouting,

"Danger!"

it gradually learns,

"This isn't something I need to overreact to."

That process takes time—but for many dogs, it can make a meaningful difference.

When Is Allergy Testing Most Helpful?

I usually recommend discussing allergy testing when:

• Environmental allergies have been diagnosed.
• Symptoms occur year after year.
• Long-term treatment is expected.
• Owners are interested in allergy immunotherapy.
• Itching remains difficult to control despite appropriate management.

When Is Allergy Testing Usually Not Helpful?

Testing is generally not my first recommendation when:

• Fleas haven't been controlled.
• Skin infections are still present.
• A food allergy hasn't been ruled out when appropriate.
• The diagnosis of atopic dermatitis is still uncertain.
• Owners are hoping the test will identify a specific food to avoid.

Questions I Encourage Every Owner to Ask

If your veterinarian recommends allergy testing, consider asking:

• What are we hoping to learn from this test?
• Will the results change my dog's treatment plan?
• Are we considering allergy immunotherapy?
• Have we ruled out other causes of itching?
• Should we see a veterinary dermatologist?

The Bottom Line

Allergy testing is an important tool, but it's often misunderstood.

It is not used to diagnose environmental allergies or food allergies.

Instead, it helps identify environmental allergens so a customized allergy immunotherapy plan can be developed for dogs with confirmed atopic dermatitis.

When used for the right patient at the right time, allergy testing can be an important step toward long-term allergy management.

Key Takeaways