During allergy skin tests, your skin is exposed to suspected allergy-causing substances (allergens) and is then observed for signs of an allergic reaction.
Along with your medical history, allergy tests may be able to confirm whether a particular substance you touch, breathe, or eat is causing symptoms.
Allergy skin tests are widely used to help diagnose allergic conditions, including:
Hay fever (allergic rhinitis)
Allergic asthma
Dermatitis (eczema)
Food allergies
Penicillin allergy
Bee venom allergy
Skin tests are generally safe for adults and children of all ages, including infants. In certain circumstances, though, skin tests aren’t recommended. Your doctor may advise against skin testing if you:
Have ever had a severe allergic reaction. You may be so sensitive to certain substances that even the tiny amounts used in skin tests could trigger a life-threatening reaction (anaphylaxis).
Take medications that could interfere with test results. These include antihistamines, many antidepressants and some heartburn medications. Your doctor may determine that it’s better for you to continue taking these medications than to temporarily discontinue them in preparation for a skin test.
Have certain skin conditions. If severe eczema or psoriasis affects large areas of skin on your arms and back — the usual testing sites — there may not be enough clear, uninvolved skin to do an effective test. Other skin conditions, such as dermatographism, can cause unreliable test results.
Blood tests (in vitro immunoglobulin E antibody tests) can be useful for those who shouldn’t or can’t undergo skin tests. Blood tests aren’t used for penicillin allergy.
In general, allergy skin tests are reliable for diagnosing allergies to airborne substances, such as pollen, pet dander and dust mites. Skin testing may help diagnose food allergies. But because food allergies can be complex, you may need additional tests or procedures.
Types of allergens
Allergens are substances that can cause an allergic reaction. There are three primary types of allergens:
Inhaled allergens affect the body when they come in contact with the lungs or membranes of the nostrils or throat. Pollen is the most common inhaled allergen.
Ingested allergens are present in certain foods, such as peanuts, soy, and seafood.
Contact allergens must come in contact with your skin to produce a reaction. An example of a reaction from a contact allergen is the rash and itching caused by poison ivy.
Allergy tests involve exposing you to a very small amount of a particular allergen and recording the reaction.
Insect sting allergy tests
Why allergy testing is performed
Allergies affect more than 50 million people living in the USA, according to the American College of Allergy, Asthma, and Immunology. Inhaled allergens are by far the most common type. Seasonal allergies and hay fever, which is an allergic response to pollen, affect more than 40 million Americans.
The World Allergy Organization estimates that asthma is responsible for 250,000 deaths annually. These deaths can be avoided with proper allergy care, as asthma is considered an allergic disease process.
How allergy testing is performed
An allergy test may involve either a skin test or a blood test. You may have to go on an elimination diet if your doctor thinks you might have a food allergy.
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Skin tests
Skin tests are used to identify numerous potential allergens. This includes airborne, food-related, and contact allergens. The three types of skin tests are scratch, intradermal, and patch tests.
Your doctor will typically try a scratch test first. During this test, an allergen is placed in liquid, then that liquid is placed on a section of your skin with a special tool that lightly punctures the allergen into the skin’s surface. You’ll be closely monitored to see how your skin reacts to the foreign substance. If there’s localized redness, swelling, elevation, or itchiness of the skin over the test site, you’re allergic to that specific allergen.
If the scratch test is inconclusive, your doctor may order an intradermal skin test. This test requires injecting a tiny amount of allergen into the dermis layer of your skin. Again, your doctor will monitor your reaction.
Another form of skin test is the patch test (T.R.U.E. TESTTrusted Source). This involves using adhesive patches loaded with suspected allergens and placing these patches on your skin. The patches will remain on your body after you leave your doctor’s office. The patches are then reviewed at 48 hours after application and again at 72 to 96 hours after application.
Blood tests
If there’s a chance you’ll have a severe allergic reaction to a skin test, your doctor may call for a blood test. The blood is tested in a laboratory for the presence of antibodies that fight specific allergens. This test, called ImmunoCAP, is very successful in detecting IgE antibodies to major allergens.
Elimination diet
An elimination diet may help your doctor determine which foods are causing you to have an allergic reaction. It entails removing certain foods from your diet and later adding them back in. Your reactions will help determine which foods cause problems.
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The Human Immune System
The human immune system is composed of three principle branches: Innate Immunity, Cellular (or T cell) Immunity and Humoral (or B cell) Immunity.
Despite these three branches and the multitude of immune cell types, the diagnostic world has only largely embraced antibodies. Leveraging our T-SPOT technology, Oxford Immunotec is one of the few companies to focus on standardising T cell and innate immunity measurements. Our T-SPOT technology gives us a unique toolbox to develop proprietary tests based on prosecuting the previously unexploited T cell and innate immunity branches of the immune system.
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Because we always standardise the number of cells used in each assay, we can compare responses over time to a common standard. It is this normalisation of the sample that makes longitudinal measurement valid and the platform well-suited for monitoring applications.
The sensitivity of the T-SPOT platform, as well as its use for monitoring applications, are two of many reasons why this technique has key advantages over other technologies, such as ELISA.
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The T-SPOT.TB test is a single-visit blood test for TB screening and is one of only two recommended alternatives to the tuberculin skin test (TST) – otherwise known as purified protein derivative (PPD) test, or the Mantoux test. The T-SPOT.TB test is available in over 50 countries including Europe, China, Japan, and the US, and is recognized by the WHO as one of the 100 essential diagnostic tests that should be available in every country. The T-SPOT.TB test uses a standardized sample, reducing the influence of factors in the blood which may affect performance, and normalizing for cell number variation.
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About Oxford Immunotec
Oxford Immunotec Global PLC is a global, high-growth diagnostics company. We bring energy and invention to a world in need of diagnostic truth. Our leading product, the T-SPOT.TB test is used for diagnosing infection with Tuberculosis, the world’s largest cause of death from infectious disease. The T-SPOT.TB test has been approved for sale in over 50 countries, including the United States, where it has received pre-market approval from the Food and Drug Administration, Europe, where it has obtained a CE mark, as well as Japan and China.
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