Differences Between An Allergy Blood Test Vs Skin Test

Allergies are a common health concern affecting millions of people worldwide. Whether it's a pollen allergy in spring or a food allergy, understanding your body's allergic reactions is crucial for managing your health effectively. Two commonly used methods for allergy testing are a blood test and a skin test.

Continue reading as we discuss the differences between an allergy blood test vs skin test, preparing for them, the process, their accuracy, benefits, and challenges. We’ll also discuss the types of allergens that can be tested by a blood vs skin allergy test, as well as which is best suited for various situations.

What Is an Allergy Blood Test vs Skin Test?

If you’re unfamiliar with the processes involved in determining allergies, you may be wondering “What is an allergy blood test vs skin test?” An allergy blood test and a skin test are both diagnostic methods used to identify allergens that trigger allergic reactions in individuals. While these tests serve the same purpose, they differ in their approach.

An allergy blood test involves taking a blood sample to measure the presence of specific antibodies related to allergies, while a common form of skin test entails applying a small amount of allergen extract to the skin and observing the skin's reaction to determine allergic sensitivities.

These tests help your doctor or allergist pinpoint the allergens responsible for an individual's allergic reactions, aiding in proper diagnosis and treatment. While skin tests are administered on-site by a professional, you can use a home allergen test analyzed by a CLIA-certified lab to identify your allergies from the comfort of your home, or you can be tested in a laboratory like Quest or Labcorp.

Advantages of Blood vs Skin Allergy Test

The choice between an allergy blood test vs skin test depends on individual circumstances and the specific allergens being tested. Each method has its advantages, and the decision should be made in consultation with an allergist or healthcare professional to ensure the most accurate and suitable diagnostic approach.

Blood Allergy Test Advantages

Some advantages of taking a blood vs skin allergy test include:

• No skin contact: Blood tests do not require direct contact with allergens, making them suitable if you have a skin condition or might react strongly to skin exposure.
• Medication compatibility: Blood tests don’t require discontinuing medications, making them a better option if you rely on medications to help manage allergy symptoms.
• Test a wide range of allergens: Blood tests can detect a broader spectrum of allergens, including food, environmental, and drug allergies, making them versatile for diagnosing various allergic conditions.
• Less invasive and safer: Drawing blood is less invasive than skin prick tests, making blood allergy tests more comfortable for people, including children and those with a fear of needles.
• Objective results: Blood tests provide quantitative data on the level of allergen-specific antibodies (IgE) present in your bloodstream. This objective measurement helps your allergist or doctor make informed diagnostic and treatment decisions for your care.

Skin Allergy Test Advantages

Taking a skin vs blood allergy test does have a few benefits of its own. Some advantages to a skin vs blood allergy test are:

• Faster results: Skin tests typically provide immediate results, allowing for quick diagnosis during the same appointment. Blood allergy tests need to be analyzed by a lab, but provide objective data for diagnosis.
• Sensitivity: Some skin tests may be more sensitive to certain allergens, which means a higher likelihood of a positive test, which includes false positive results.  This is tricker, however, because a positive test doesn't mean you have an allergy, and it needs to be interpreted in the context of your clinical history.
• Minimal discomfort: Some types of skin allergy tests may be more comfortable if you are averse to drawing blood. However, taking an allergy blood test vs skin test requires less pricking and fewer needles overall.

Detailed Comparison of Blood vs Skin Allergy Test

There are various factors to consider when taking an allergy blood test vs skin test. It’s important to understand the differences between these two methods including types of tests for each, preparation, process, and accuracy.

1. Types of Allergy Blood Test vs Skin Test

Allergy testing is not a one-size-fits-all approach, and the choice between blood and skin tests is just the beginning. Within each category, there are various types of tests, each with its own advantages and considerations.

Types of Blood Allergy Tests

• Serum allergen-specific IgE concentrations: This allergy blood test analyzes the levels of specific IgE antibodies against various allergens in the blood. This blood can be drawn from your doctor's office or at an allergy testing lab like Quest or Labcorp.  If you opt for a home test, make sure your test is from a CLIA-certified lab to ensure accuracy, precision, and reliability in their testing. Not all tests are created equal and may provide inadequate results.
• Immunoglobulins blood test (IgG): This type of blood test is used to analyze the IgG antibodies to specific foods present in your blood. At this time, IgG antibodies are not considered reliable for identifying food allergies, intolerance, or sensitivities. Most people produce IgG antibodies after eating food and it’s not recommended as a diagnostic tool.

Types of Skin Allergy Tests

• Skin-prick tests (SPT): The most common type of skin allergy test. This test involves placing a small amount of allergen extracts on the skin's surface and then pricking or scratching the skin to allow the allergens to enter. A raised bump or redness means a patient is sensitized to that allergen.
• Patch Test: This kind of skin allergy test is primarily used to diagnose allergies to products that come into direct contact with your skin and cause a rash, known as contact dermatitis. The test administrator will apply an allergen-containing patch to the skin for a period of time. Reactions like redness or irritation indicate a sensitivity to the tested allergens. The patch stays on your back for 48 hours and is removed and read in a doctor's office.
• Intradermal tests (IDT): A more invasive type of allergy skin test that involves injecting a small amount of allergen extract just beneath the skin's surface to assess the body's immune response. This is most often used when skin prick tests yield inconclusive results or to detect allergens with low sensitivity thresholds (the amount of an allergen your body can tolerate without producing a reaction). This type of testing is done for environmental allergies, but not with foods due to a risk of anaphylaxis.

2. Preparing for Your Allergy Test

Before undergoing an allergy test, it’s important to understand how to prepare for it. When comparing an allergy blood test vs skin test, how you prepare can impact the accuracy and reliability of the results.

Blood Allergy Test

• No specific preparations: There are typically no specific preparations needed before a blood allergy test, making it a simpler option for many.
• No restrictions: Blood allergy tests do not require any dietary or medication restrictions prior to testing, making them more convenient if you cannot discontinue medications or adjust your diet beforehand.

Skin Allergy Test

• Minimal preparation: Preparing for a skin allergy test usually involves informing your allergist about any medications you're taking that might interfere with the test.
• Stop taking antihistamines: You may need to avoid antihistamines for a specified period before the test, as they can reduce skin reactions. This is usually a period of 5-7 days, but consult your allergist or doctor for exact guidance.

3. Allergy Test Process

The allergy testing process for a blood vs skin allergy test can vary significantly. Each method offers unique insights into your allergen sensitivities, but understanding the differences in the testing process is key to making an informed choice.

Blood Allergy Test

• Blood sample: In a blood allergy test, your allergist draws a blood sample from a vein in your arm. For home allergy tests, you will provide your own blood sample according to the instructions provided, such as pricking your finger.
• Laboratory analysis: The blood sample is sent to a laboratory where it is analyzed to measure the levels of specific antibodies, called IgE antibodies, produced in response to allergens.

Skin Allergy Test

• Skin exposure: During a skin allergy test, a small amount of allergen extract is applied to the skin's surface, often on the forearm or back.
• Skin prick or scratch: The skin is then pricked or scratched to allow the allergen to enter. The doctor observes the skin for any allergic reactions, such as redness, swelling, or hives, which usually occur within 15-20 minutes.
• Intradermal injection: A small amount of allergen extract is injected right beneath the skin's surface to assess the body's immune response. This is not as common and is usually only used when another type of skin test is inconclusive.

Skin tests most often accompany diagnoses during the same appointment, yielding rapid tests based on the doctor’s or allergist’s determination.

4. Accuracy

How accurate are blood allergy tests vs skin tests? Each comes with its own methods for assisting your doctor or allergist in making a diagnosis. In addition to your test, your doctor or allergist will consider your full allergy history of reactions for accuracy. The two together are what diagnoses an allergy.

Blood Allergy Test Accuracy

• Accurate results: Results from blood tests may take longer, often a few days to a week, to be available. These results show objective data versus the more subjective analysis of skin tests.
• High accuracy: Blood allergy tests (IgE tests) are generally considered accurate for identifying allergen sensitivities. On average, allergy blood test accuracy demonstrates sensitivity rates ranging from 70% to 90%, and specificity rates ranging from 40% to 100%(1).

How accurate are blood allergy tests provided by Nectar compared to others? Our home allergy test provides a value between 0-255 for each allergen tested. Whatever range you fall into is categorized into a “Class,” indicating how severe your sensitivity to an allergen may be. Each “Class” then falls into a “Reactivity Level” that ranges from “Very Low” to “Very High,” providing you with more information about which allergens affect you the most.

Skin Allergy Test Accuracy

• Subjective results: They provide immediate results, making them especially valuable for diagnosing environmental allergens such as pollen or pet dander. However, it is dependent on the age of the testing extracts, the type of device used, and the person reading the test. So much of the skin test is what we call user-dependent.
• Varying accuracy: Different skin allergy tests may yield different accuracy levels. For example, an estimated 50-60 percent of all skin prick tests (SPT tests) yield some “false positive” results. This means the test shows positive when you’re not allergic to the allergen being tested(2).

Allergens Identified By a Skin vs Blood Allergy Test

Deciding between taking an allergy blood test vs skin test might depend on which allergens you’d like to test for.

The benefit of a blood vs skin allergy test is that one blood test can be used against one or multiple allergens at once. For example, our at home allergy test helps identify 40 different indoor and outdoor allergens.

A skin prick test, on the other hand,  is often used to detect type I reactions related to food and aeroallergens while the patch test is frequently used to detect type delayed allergic reactions, which are allergens responsible for skin conditions like contact dermatitis(3).

Choosing Between an Allergy Blood Test vs Skin Test

When faced with the decision between an allergy blood test vs skin test, it's important to consider a few key factors. The choice largely depends on your specific situation and the allergens you suspect are causing your symptoms.

Skin tests are ideal for identifying environmental allergens like pollen and cat dander, while also being suitable for insect venom allergies. They offer rapid results and high sensitivity. On the other hand, allergy blood tests provide a broader range of allergens to be tested, making them excellent for diagnosing a wide array of indoor and outdoor allergies. They are particularly beneficial when discontinuing medications is not an option.

Knowing the differences between an allergy blood test vs skin test is the first step toward managing your symptoms efficiently and effectively. Your doctor or allergist can advise you in selecting the most appropriate method based on your symptoms, medical history, and the allergens you need to identify.  This will ensure an accurate diagnosis and effective allergy treatment.

Bonus Note: Don’t want to take another blood allergy test or skin test when you’ve already had one? Nectar accepts uploads of prior tests for allergy treatment assessment.

Additional Sources

1. https://aafa.org/allergies/allergy-facts/
2. https://www.foodallergy.org/resources/skin-prick-tests
3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8346756/