What are allergies?
Do you sneeze every time you pet a dog? Do you break out in a rash when eating peanuts? If yes, you may already know what allergies are. Alternatively, you may also experience allergy symptoms but are unsure of where they are coming from. Research suggests that the prevalence of individuals with allergies is increasing worldwide.1 One study showed that the prevalence of food-related and inhalation-related allergies was 24.9% and 26.7%, respectively.2
Allergies are caused by hypersensitivity of the immune system to typically harmless substances in the environment.3 These seemingly harmless substances are known as allergens. There are four types of allergens: inhalants, contactants, ingestants, and injectants.3 Inhalants are allergens you breathe in including pollen, mold, dog dander, and bird feathers.3 Contactants are allergens that irritate your skin upon direct contact such as dyes, fabrics, or poison from a plant.3 Ingestants most commonly refer to food or medication allergens such as shellfish, peanuts, milk, or antibiotics (i.e., amoxicillin).3 Injectants could also refer to medications but also include bug bites or insect venom that penetrate the skin.3 Now that we know what allergens exist, it is important to consider how they are diagnosed and what symptoms you can expect.
Allergy symptoms may be mild or moderate such as runny/stuff nose, sneezing, coughing, or rash.4 Some allergies can trigger a severe reaction known as anaphylaxis.5 Anaphylaxis is a life-threatening medical emergency and immediate action should be taken.5 It can result in loss of consciousness due to a sudden drop in blood pressure, swelling of the lips, tongue, or throat, and chest tightness or difficulty breathing.5
What is allergy testing?
If you have symptoms that you think are caused by an allergy, your doctor may recommend a specific allergy test, or you can purchase an at-home allergy test.
Allergy tests measure your immune system’s response to certain allergens or triggers. When exposed to these allergens or triggers, your body overreacts and produces antibodies called immunoglobulin E (IgE).6 IgE antibodies can even be detected before symptoms are present.7 This is called IgE sensitization and often occurs prior to the development of a clinical allergy.7 Upon re-exposure to the same allergen, the IgE binds to the surface of mast cells which are typically found in skin and mucosal tissues.6 When the allergen binds to IgE, the immune system triggers a rapid memory response and histamine (and other chemicals in your body) is released, leading to allergy symptoms.6 This is why people often take medications known as antihistamines like Allegra®, Claritin®, or Benadryl® which block the action of histamine to provide relief from common allergy symptoms.6
What are the types of allergy tests?
There are two main allergy testing methods that can assess the presence of allergen-specific IgE antibodies: skin-prick test or blood test.
With the skin prick test, your clinician would prick the skin with a puncturing device containing a small amount of a suspected allergen.8 Common areas for pricking include the back or the inner side of the forearm.8 A test is considered positive for a particular allergen if a person has a visible reaction (redness, itching, hives) typically within 30 minutes.8
If a skin test cannot be done or if you are looking for an alternative, an allergy blood test can be ordered. This method is often more favorable for infants and pediatrics than multiple skin pricks. Once a patient’s blood is drawn, it is sent to the laboratory for analysis, and results are sent back to the clinician for review. The laboratory method most used is an enzyme-linked immunosorbent assay (ELISA). The ELISA test uses specific IgE antibodies to detect immune response in the body.9 With a single sample of blood, multiple allergens can be detected simultaneously.9 This is seen with the EUROLINE (Specific IgE) Allergy test which can detect up to 54 allergens in a single run. EUROIMMUN’s portfolio contains over 400 different allergens and these EUROLINE profiles are available for various regions and commonly seen food and inhalation allergens.
The EUROLINE Allergy test measures the concentration of specific IgE antibodies in blood.9 With the EUROLINE test, the concentration is semi-quantifiable and correlates with a specific class system called enzyme-allergosorbent test (EAST) in classes from 0-6 and concentrations from 0.35-100 kU/L.10 For example, a class 0 would correlate with a concentration <0.35 kU/L while a class 6 would denote a concentration of >100 kU/L.10 Typically, a result correlating with a class 3 or greater designates significant level of antibodies detected which is indicative of an allergy.10
Combining an IgE-antibody blood test result with case history and a physical examination has clear clinical advantages when making a diagnosis. Before making a conclusive diagnosis, it is important to consider other factors such as age (more common in younger children), family history, stress, previous symptoms, and other triggering allergens.
How do at-home tests work?
With the rise in precision medicine and direct-to-consumer testing, it is now possible and easy to do an allergy test from the comfort of your own home. If you suspect food or inhalation allergies, you may take it upon yourself to order an at-home allergy test.11 The test kit will include a dried-blood spot (DBS) card. The patient will collect blood from his/her finger using a sterile lancing device and input the blood onto the designated blood spot circles.11 Once ensuring the procedure is followed and the circles are sufficiently filled, the completed DBS card is mailed to the laboratory for testing.11 The laboratory then performs the necessary allergy testing and the results are shared with a physician.11 Finally, the physician discusses these test results with the patient and appropriate actions are taken if allergies are present. The at-home test is a great option as it is less invasive, cost-effective, and can receive accurate results from the comfort of your home. Many of these at home tests can be ordered online or picked up at your local Target, CVS, Walgreens, etc.
Allergy testing identifies common allergens including foods (i.e., peanuts, shellfish, milk) and inhalation (i.e., pet dander, mold, bee stings) that are often harmless but may cause allergies in some patients. There are two main allergy testing methods, skin-prick and blood tests, that can assess the presence of allergen-specific IgE antibodies. Combining an IgE-antibody blood test result with case history and a physical examination has clear clinical advantages when making a diagnosis. Additionally, it is now possible and easy to do an allergy test from the comfort of your own home using DBS cards for blood collection and further review by a physician.
- Immunology AAoAA. Allergy Statistics. https://www.aaaai.org/About/News/For-Media/Allergy-Statistics. Published 2021. Accessed September 16, 2021, 2021.
- Enroth S, Dahlbom I, Hansson T, Johansson Å, Gyllensten U. Prevalence and sensitization of atopic allergy and coeliac disease in the Northern Sweden Population Health Study. Int J Circumpolar Health. 2013;72.
- HowStuffWorks.com. The Lymph System. Allergens and Allergic Reactions Web site. https://health.howstuffworks.com/human-body/systems/lymphatic/lymph-system.htm#pt2. Updated September 23, 2009. Accessed Sept 16, 2021, 2021.
- American College of Allergy A, & Immunology. Allergy Symptoms. https://acaai.org/allergies/symptoms/. Published 2021. Accessed September 16, 2021, 2021.
- Clinic M. Allergies: Symptoms & causes. Allergies Web site. https://www.mayoclinic.org/diseases-conditions/allergies/symptoms-causes/syc-20351497. Published 2021. Updated Aug 4, 2020. Accessed September 16, 2021, 2021.
- Diseases NIoAaI. How Does an Allergic Response Work? Allergic Diseases Web site. https://web.archive.org/web/20150618023413/http://www.niaid.nih.gov/topics/allergicdiseases/Pages/allergic-Response.aspx. Published 2015. Accessed September 17, 2021, 2021.
- Wagner B, Miller WH, Jr., Erb HN, Lunn DP, Antczak DF. Sensitization of skin mast cells with IgE antibodies to Culicoides allergens occurs frequently in clinically healthy horses. Vet Immunol Immunopathol. 2009;132(1):53-61.
- Syed Shahzad Mustafa M, Allison Ramsey, MD, John P. Cunha, DO, FACOEP. Skin Test for Allergy
Skin Test for Allergy Web site. https://www.medicinenet.com/skin_test_for_allergy/article.htm#how_is_an_allergy_skin_test_done. Accessed September 17, 2021, 2021.
- Siles RI, Hsieh FH. Allergy blood testing: A practical guide for clinicians. Cleveland Clinic Journal of Medicine. 2011;78(9):585-592.
- Popescu FD, Vieru M. Precision medicine allergy immunoassay methods for assessing immunoglobulin E sensitization to aeroallergen molecules. World J Methodol. 2018;8(3):17-36.
- Allergytest.co. How to take a sample: For blood spot testing. Blood spot instructions Web site. https://allergytest.co/blood-spot-instructions/. Accessed September 17, 2021, 2021.