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What To Expect from an Allergy Test

Allergens are specific substances that cause your immune system to overreact. This triggers allergy symptoms such as sneezing, itching, swelling, hives, and wheezing. Allergy testing can identify the allergens that are causing your symptoms.

Allergy specialists typically conduct allergy testing based on your medical history and allergy symptoms. There are several methods used to test for allergies. Understanding what to expect and how to use your test results to improve your symptoms is important. This information can be used to develop personalized treatment plans.

Types of Allergy Testing 

Allergy testing is conducted for both food and environmental allergies, though environmental allergy testing is more common.

Common allergy testing methods include:1,2,3

  • Skin prick tests: The skin is pricked, and a small amount of the allergen is placed over the nick. The area is observed for signs of an allergic reaction, such as a red bump.
  • Intradermal skin test: Allergen is injected under the skin’s surface, and the areas are observed for an allergic reaction. Intradermal tests are more sensitive and are used if a prick test results are inconclusive.
  • Blood test: Enzyme-linked immunosorbent assay (ELISA) or radioallergosorbent test (RAST) measures the levels of immunoglobulin E (IgE). Elevated IgE antibodies directed toward a specific antigen can indicate an allergic response.
  • Patch tests: Allergens are applied to an adhesive patch which is left in place for 48 to 96 hours. The patch is removed, and the area is examined for signs of an allergic reaction. Patch tests identify allergens that cause contact dermatitis, a delayed allergic reaction.
  • Provocation tests: This is a carefully controlled test conducted in an allergist’s office. It involves ingesting a small amount of an allergen and observing for any allergic responses.

Home allergy tests are also available. These tests are convenient because you collect a sample, usually a blood sample, at home and send it to the lab for evaluation. The lab will process the sample and report your IgE levels for suspected food and environmental allergens.

Allergy testing is not used alone to diagnose allergies. Clinical context is required. Telehealth makes this easy by providing access to a doctor available 24 hours a day. You can speak with a doctor on call about your allergy test results, receive an online prescription, if appropriate, and receive individualized guidance on how to minimize your allergy symptoms.

Preparing for an Allergy Test

To ensure you get the most accurate allergy testing results, take these steps to prepare:3

  • Provide your allergist or other healthcare provider with a detailed history of your allergy symptoms and exposures.
  • Provide a list of all medications you are taking, including over-the-counter, to verify whether any might interfere with your allergy testing.
  • Stop taking any antihistamines for 5 to 10 days before your allergy testing. Antihistamines reduce histamine release and the immune response, which affects some allergy test results.
  • Do not apply any topical steroids to the testing site for 2 to 3 weeks.
  • If you are having food allergy testing, ask if you should avoid consuming suspected foods for several days before your testing.
Prick test for allergies

How Is Allergy Testing Done

The procedure for allergy testing varies based on the type of test. Before the test, your allergist will review your medical history to determine which allergens should be tested. Suspected food, environmental and medication allergens can be tested.3

The most common allergy testing done is skin prick testing:4

  • Skin testing is typically done on the arm or back.
  • The skin is cleansed, marked, and labeled for allergens.
  • A small drop of allergen is placed in a labeled area.
  • The skin is abraded with a needle (prick).
  • A small drop of histamine is typically used as a positive control, and saline is used as a negative control.
  • The results are noted and scored after about 15 minutes.

Intradermal test:

  • The procedure is similar to a skin prick test. The major difference is that a small amount of allergen is injected just under the top layer of the skin.

Patch tests:3

  • A patch impregnated with an allergen is applied to the back.
  • The results are read at 48 and 96 hours. Sometimes, the patch test results are read again at seven days.
  • Sweating and wetting the patch can cause the patch to dislodge.

Skin tests are more sensitive than blood tests. A skin test is more likely to identify your allergy if you are allergic to a substance than a blood test. Skin tests are conducted in an allergist’s office. These tests are extremely safe, and severe allergic reactions are rare. An allergist’s office is equipped with medications that can control a severe reaction should it occur.4  

Patch test for allergies

Blood test:

  • A blood sample is taken, either in a lab or at home. At-home tests usually instruct the test user to use a lancet and prick their finger to obtain a sample.
  • The blood sample is sent to the lab in a small vial or on a paper card.
  • Results are usually reported on an online portal.
  • Blood tests are readily available, require only a single blood draw, do not require training to administer, and the results are not affected by whether you have taken an antihistamine.

Interpreting Allergy Test Results

Allergy testing requires context. Most allergy tests are very accurate at excluding allergens that are not responsible for an allergic reaction but are not as good at identifying specific allergens.3 Both skin and blood tests can indicate that you are allergic to a substance when you are not. This is more common in food allergy testing. In many cases, your body has created IgE antibodies to a substance, but this does not necessarily mean your immune system will react to the substance.

In addition to taking an allergy test, it is essential to work with an allergist to develop a personalized treatment plan. Based on your symptoms and your allergy test results, your online doctor can diagnose allergies and prescribe the right medications to relieve your symptoms.

A patient talking with a doctor

Follow-up After an Allergy Test

Allergy testing can identify substances you are allergic to and, as importantly, substances you are not, but testing is only the first step. It is important to schedule an appointment with a healthcare provider to review your test results and develop a management plan. They may suggest environmental modifications, medications, or allergy immunotherapy (allergy shots).

Disclaimer

While we strive to always provide accurate, current, and safe advice in all of our articles and guides, it’s important to stress that they are no substitute for medical advice from a doctor or healthcare provider. You should always consult a practicing professional who can diagnose your specific case. The content we’ve included in this guide is merely meant to be informational and does not constitute medical advice.

References:

1. Portnoy JM. Appropriate allergy testing and interpretation. Mo Med. 2011 Sep-Oct;108(5):339-43. PMID: 22073491; PMCID: PMC6188374.

2. Ansotegui IJ, Melioli G, Canonica GW, et al.. IgE allergy diagnostics and other relevant tests in allergy, a World Allergy Organization position paper. World Allergy Organization Journal. 2020;13(2):100080. doi:10.1016/j.waojou.2019.100080

3. Muthupalaniappen L, Jamil A. Prick, patch or blood test? A simple guide to allergy testing. Malays Fam Physician. 2021 May 31;16(2):19-26. doi: 10.51866/rv1141. PMID: 34386160; PMCID: PMC8346756.

4. Kowalski M, Ansotegui I, Aberer W, et al. Risk and safety requirements for diagnostic and therapeutic procedures in allergology: World Allergy Organization Statement. World Allergy Organization Journal, 2016; 9(1):33. doi:10.1186/s40413-016-0122-3

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