In a very recent study looking at the prevalence, diagnosis, and management of food allergies, it found that “the evidence for the prevalence and management of food allergy is greatly limited by a lack of uniformity for criteria for making a diagnosis.”1 Interestingly, the study also stated that there is not a universally accepted definition of food allergy!1
There are several food allergy tests out there to make a diagnosis of a food allergy. It can be difficult sometimes to determine which one will help get the most accurate diagnosis for you or your little one. Today we will cover what the most common tests are and how they work.
The most common allergy diagnosis tests are skin prick testing, total serum (blood) IgE testing, and atopic patch testing. An oral food challenge is also an effective test for food allergy diagnosis, but it has its limitations.
Here is a list of how each test works and some of the advantages and disadvantages of each one. Some of these tests can be less accurate in young children, so remember to talk with your doctor about which option(s) is best for your child.
Skin Prick Tests (SPT) – Direct challenge of allergen on skin with a needle prick. Most commonly used method.
Advantages: Rapid results, may apply many allergens, easy to perform.2
Disadvantages: Affected by use of antihistamines, false positives are noted, potential risk of anaphylactic reactions, not ideal for those with extensive eczema, trained professional must administer.2
Total Serum IgE (RAST or ELISA) – Sample of blood is taken to measure IgE amounts.
Advantages: More comfortable than skin tests, no risk of anaphylaxis, unaffected by medication use.
Disadvantages: Tests results delayed, requires large volume of blood for multiple tests which may be harder for younger children, high cost, fewer allergens tested.
Atopic Patch Test (APT) – Skin exposure to allergen over long period of time (24 – 72 hours). Used to assess non-IgE food allergy responses.
Advantages: Assesses late onset of symptoms, can help to identify allergens for patients with Eosinophilic Esophagitis or Atopic Dermatitis.
Disadvantages: Highly variable in testing method, preparations and results.
Oral Food Challenge – Specific foods are introduced to patient and symptoms are assessed. Must be a double blind placebo controlled food challenge.
Advantages: The most accurate testing method for food allergies, criterion standard.
Disadvantages: Risk of anaphylactic reactions, significant amount of time and man power needed, cost, facility must have proper tools and equipment to perform this test.
Quick tip: If you’re new to oral food challenge doctor visits, these visits can sometimes last 3 to 4 hours. One food allergy parent we spoke with said she was caught off guard and unprepared for how long the visit was. If you’re taking your little one in for food allergy challenges, make sure that you bring some items to entertain them, such as books, crafts, or a handheld game device. This can help you and them to pass the time, as you wait to see if there are any reactions to different amounts of the food being challenged.
At times, some physicians may perform more than one type of test to ensure the most accurate results.
Have you had experience with any of these tests? Which did you find to be most accurate for your little ones?
1. Schneider Chafen, J et al. Diagnosing and Managing Common Food Allergies: A Systematic Review. JAMA 2010;303(18):1848-1856
2. Huang, Shih-Wen, Allergy Testing in Children; Which Test When?. Consultant for Pediatricians 2010;9(3);93-100