Allergy blood test: A GP’s guide

Allergies can range from mildly inconvenient to potentially life-threatening, making accurate diagnosis and management essential. Allergy blood testing is one of the tools healthcare providers use to identify allergens and guide treatment plans. In this guide, we’ll explore the ins and outs of allergy blood tests, from what they are to when they’re needed and how they compare to other testing methods.

What is allergy testing?

Allergy testing helps identify substances—known as allergens—that trigger allergic reactions in your body. Allergens can be foods, pollen, pet dander, or even medications. When exposed to an allergen, your immune system might overreact, releasing chemicals like histamine that cause symptoms such as itching, sneezing, or swelling. There are two primary methods of allergy testing:

• Skin testing (a physical reaction test)
• Blood testing (measuring immune responses in a lab)

In this post, we’ll focus on blood tests, a non-invasive option often recommended for individuals who cannot undergo skin testing.

Also read: Common seasonal allergy symptoms & the best ways to deal with it?

 

Types of allergy blood tests

Two main types of allergy blood tests are commonly used:

1. Total IgE test

This test measures the overall level of immunoglobulin E (IgE) antibodies in your blood. Elevated IgE levels suggest your immune system is reacting to one or more allergens, though it doesn’t pinpoint the specific trigger.

2. Specific IgE test

This test targets specific allergens. For example, if you suspect a peanut allergy, a specific IgE test can confirm if your immune system reacts abnormally to peanuts. Panels are also available for groups of common allergens, such as tree pollen, animal dander, or food.

When is allergy testing usually needed?

Allergy testing may be recommended if you experience:

• Unexplained skin reactions, like hives or eczema.
• Recurring respiratory symptoms, such as sneezing, nasal congestion, or wheezing, unrelated to infections.
• Severe food reactions, including anaphylaxis.
• Chronic symptoms, like year-round nasal congestion, which might point to indoor allergens.

Testing is especially important when symptoms significantly impact daily life or present a risk to safety (e.g., severe peanut or insect sting allergies).

Can allergies be detected in blood tests?

Yes, blood tests can detect allergies by measuring the level of IgE antibodies specific to certain allergens. While they don’t diagnose allergies outright, they provide strong evidence of sensitisation. A high IgE level indicates your immune system recognises and reacts to the tested allergen, although the severity of symptoms may vary.

Is allergy blood test covered by Medicare?

In Australia, Medicare may cover allergy blood tests if deemed medically necessary by a GP or specialist. Coverage typically applies to specific IgE tests rather than broad screening panels. Always confirm with your healthcare provider and Medicare for your eligibility, as private fees may apply for certain tests.

How does an allergy blood test work?

Allergy blood tests analyse a small sample of blood to detect IgE antibodies. When your immune system encounters an allergen, it produces these antibodies as part of its defense mechanism. In the lab, the sample is exposed to allergens, and the reaction is measured to determine sensitivity.

How do I prepare for an allergy blood test?

One of the advantages of blood tests over skin tests is minimal preparation. You don’t need to stop antihistamines or other allergy medications before the test, as they won’t interfere with the results. However, it’s always wise to consult your GP for specific instructions.

What happens during an allergy blood test?

The process is straightforward and typically involves:

1. Blood draw: A healthcare provider uses a needle to collect blood, usually from a vein in your arm.
2. Lab analysis: The sample is sent to a lab, where it’s tested against suspected allergens.
3. Results: The lab provides a report detailing IgE levels for each allergen, which your GP will interpret.

The procedure is quick and relatively painless, with results available in a few days

What do allergy blood test results mean?

Results are reported in classes (Class 0 to Class 6), corresponding to IgE levels:

• Class 0: No sensitivity detected.
• Class 1–2: Low to moderate sensitivity.
• Class 3–6: High sensitivity, often correlating with more severe allergic reactions.

It’s crucial to remember that a positive result doesn’t always mean you’ll experience symptoms. Conversely, a negative result doesn’t completely rule out allergies. Interpretation should always be done in context with your symptoms and medical history.

When should I consult a doctor?

Consult your GP if you:

• Suspect you have allergies based on recurring symptoms.
• Experience severe reactions, such as anaphylaxis, requiring emergency care.
• Need guidance on managing diagnosed allergies or considering testing options.

Also read: How to stop allergies naturally?

Can an online GP refer to the allergy test?

Yes, online GPs can refer you for allergy blood tests in most cases. Telehealth consultations are a convenient option for discussing symptoms, exploring testing options, and obtaining a referral. However, follow-up care or specialist consultation may still be needed, depending on the results.

Other allergy testing methods

While blood tests are valuable, they aren’t the only option:

• Skin prick testing: A small amount of allergen is applied to the skin, and the area is observed for a reaction. It’s quick but not suitable for people with severe allergies or skin conditions.
• Oral food challenge: Conducted under medical supervision, this involves consuming small amounts of a suspected allergen to monitor for reactions.
• Patch testing: Used for delayed reactions, such as contact dermatitis, this involves applying allergens to the skin and observing over 48–96 hours.

Each method has pros and cons, and your GP can help determine the best approach for your situation.

How can an online doctor help with allergy blood tests and allergies?

Telehealth services make it easy to address allergy concerns without leaving your home. Here's how an online doctor can assist:

• Telehealth appointments: Discuss your allergy symptoms with a licensed doctor via secure video or phone instant consults from the comfort of your home.
• Allergy blood test guidance: Receive advice on whether an allergy blood test is right for you and get an online referral to a local diagnostic lab if needed.
• Medical certificate online: Get an online doctor's certificate from the comfort of your home 24 hours a day
• Online prescriptions: Get instant scripts for allergy medications like antihistamines or nasal sprays, along with the option for online pharmacy delivery at your convenience.
• Treatment recommendations: Learn about over-the-counter remedies or lifestyle changes to manage allergy symptoms effectively.
• Doctor referrals: Access referrals to specialists for further evaluation and treatment.

With telehealth, managing allergies and exploring testing options has never been more accessible or convenient!

Final thoughts

Allergy blood tests are a valuable tool for identifying allergens and managing symptoms. Whether you’re dealing with sneezing fits or life-threatening food allergies, proper diagnosis is the first step toward relief. Always work with a GP or specialist to ensure accurate testing and effective treatment. If you're curious about allergy testing, start by discussing your symptoms with a healthcare provider and they will be able to guide you down the appropriate path.