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Food Allergy, Intolerance, & Sensitivity Testing

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How to be a Good Patient Advocate Part 2: Food Allergy, Intolerance, and Sensitivity Testing

Navigating nutrition when you have crohn’s or ulcerative colitis can be overwhelming at times. Knowing how to appropriately communicate your nutrition needs to help manage your symptoms is a useful tool in being your own advocate and can result in an overall more stress-free eating experience.

Defining Food Allergies, Intolerances, and Sensitivities:

Food Allergy:

The most important aspect concerning food allergies, food intolerances, and food sensitivities, is ensuring that the word “allergy” isn’t being used loosely and should be reserved only for a true allergy, because allergies can have life-threatening symptoms, like swelling and anaphylaxis, if not vigilantly avoided. Food allergies can be divided into two different categories. Class 1 food allergens cause allergic sensitization via the digestive tract and causes a systemic response (e.g. hives, swelling).  Class 2 food allergens in food that are susceptible to changes when introduced to heat (cooking, baking) and therefore do not cause gastrointestinal sensitization. These are allergens that the person has been previously introduced from the environment (e.g. pollen), and may manifest later in life when ingesting other food pollens (e.g. apricots, apples, some raw vegetables). (1)

Food Intolerances:

Food intolerances affect about 20% of the worldwide population, but the diagnosis piece is not always straightforward, because the symptoms manifest differently from person to person, ranging from mild GI discomfort to urgent diarrhea or constipation. Generally speaking, food intolerances refer to the ability to digest a particular food, meaning something involved in the process of digestion affects the outcome of the digestion, resulting in gas, distention, or discomfort. For example, the most common food intolerance is lactose intolerance, resulting from an insufficiency of the lactase enzyme that is required to break lactose down into smaller sugar components. When the lactose can’t be broken down into smaller sugars, it passes through the colon without being broken down, resulting in bloating, gas, distention, pain, and nausea. Another example of a common food intolerance that exists pharmacologically, rather than enzymatically like a lactose intolerance, is caffeine. Caffeine may be tolerated in smaller amounts, and others may need to avoid caffeine altogether (2). Registered Dietitian Nutritionists (RDN) may help you work through an elimination diet, where foods can be temporarily eliminated from the diet to observe relief, then slowly adding them back in without putting the patient at risk for nutritional deficiencies, but this protocol may not be necessary (3). Stay tuned for more information about elimination diets in a future post! 

Food Sensitivities:

The term “food sensitivity” is not used in scientific literature and is often used interchangeably with food intolerance, but there is really no standard medical definition to denote food sensitivities, whereas food intolerances can usually be traced back to a specific enzyme deficiency.

Testing for Food Allergies, Intolerances, and Sensitivities:

A test should be supported through peer-reviewed, evidence based research that proves to be reliable, valid, specific, and sensitive. See "Chat A" for definitions of reliability, validity, specificity, and sensitivity. If a test cannot meet all this criteria, there is research to support that too, and that information is also useful in guiding future decisions and research.

Chart A

Food Allergy Testing:

There has been a rise in popularity for food-sensitivity tests, but these cannot diagnose food allergies. Please see a medical doctor to diagnose food allergies. Food allergy testing can be diagnosed in a couple of ways: skin tests and blood tests.

Skin prick testing (SPT) is the most preferred diagnostic tool for food allergies, because the results are immediate, leaving less time for error. A positive SPT is reliable about 50% of the time, but a negative SPT is about 95% predictive. The positive result means that the body is producing IgE antibodies in response to a particular substance. However, because of the low reliability, the SPT is not sufficient and must be measured against medical history and the patient’s memory of reactions to foods. Keeping a food diary, tracking the food, the amount, the time of day, and the reaction, would be a useful tool to take to your allergist for comparison (5).

SPT, blood testing IgE antibodies, together with a well-documented patient history are all useful tools in conjunction for food allergy testing. Both the IgE antibody blood test and the SPT test have good sensitivity, but low specificity, which is why, together with a thoroughly documented history of foods, time of day, and reaction manifestation, are useful tools together to identify a food allergy. The gold-standard allergy test is the Oral Foods Challenge, but this is a high-risk test that requires the supervision of an allergist for optimal safety (6).

Food Intolerance Testing:
The Hydrogen Breath Test is used most often to identify lactose intolerance, or bacterial overgrowth of the small intestine (SIBO). A past issue with the Hydrogen Breath Test was that there was no standardization, but as of 2017, more standardization has been implemented by a board of medical doctors that has strengthened the utilization of this testing procedure (7).

Food Sensitivity Testing:

Despite the increasing popularity of food sensitivity testing, there is not yet strong conclusive scientific evidence to support their use. It is worth noting that, according to the National Institute of Health, all of these tests are on the list of “non-standardized and unproven” procedures for the diagnosis of food allergies and sensitivities (8).

Here are a couple of common food sensitivity tests that warrant further explanation:


  • The Mediator Release Test is used to detect changes in the white blood cells incubated in potential trigger foods. However, white blood cells break down and release for various reasons that may not be related to the presence of an allergen. The breakdown of white blood cells would be just as likely to occur in healthy individuals as with those with true sensitivities and/or allergies (9). 
  • No well-designed controlled trials have validated the use of MRT, and most of the information in support of MRT is only listed on consumer sites (10).  There were two research studies conducted on the MRT/LEAP, a protocol of the test which includes many diet and lifestyle modifications. Unfortunately, when researchers test more than one variable in a study no conclusions can be drawn because we don’t know what the results are from. Also, in these studies there Finally, the only research that has been identified on MRT are two research abstracts (summaries) about MRT with an elimination diet protocol that were presented at conferences but were not peer-reviewed (11,12)


  • Unlike IgE-driven reactions measured through a blood test that occur immediately, IgG reactions are thought to occur from a few hours to a few days later, resulting in a host of symptoms: joint aches/pain, GI bloating/pain/diarrhea/constipation, skin irritation, headaches, and more.
  • Though not much research supports the use of IgG to diagnose and/or treat food sensitivities, there is one worth noting:
  • In a study in 2005, 150 randomized participants with irritable bowel syndrome were told to eliminate foods that corresponded with an IgG reaction on a blood test or were instructed to follow a control diet with specified foods to remove. After 3 months, the true IgG-tested group reported a 10% greater decrease in symptoms. The conclusion: IgG testing may be helpful in identifying food sensitivities and is worthy of further biomedical and clinical research. However, this study had some issues. First, the participants who eliminated the IgG-flagged foods were also told to eliminate milk and wheat products, which also invalidates the study (13). 
  • In addition, children allergic to egg and milk were more likely to outgrow these allergies if they had higher IgG levels, making this study low in specificity (14).
  • The bottom-line: IgG is actually a marker of tolerance and exposure to food. Therefore, positive test results for food-specific IgG are to be expected in normal, healthy adults and children. Additionally, the inappropriate use of this test only increases the likelihood of false diagnoses being made, resulting in unnecessary dietary restrictions and decreased quality of life (10).”
  • Common IgG tests: Everlywell (15), Pinnertest (16)

So...what’s the best way to identify your trigger foods?

If you suspect that you may have food sensitivities, work with a Registered Dietitian Nutritionist (RDN) to guide you in requesting specific labs from your doctor for an evidence-based foundation to lay the groundwork. Then, work together to replace foods, or maybe develop a plan to temporarily eliminate foods without risking nutrient deficiencies- this is a strong way to advocate for your own health without wasting money on tests that aren’t yet backed by strong science. The good news? Many patients are able to achieve symptom-remission without working through a difficult elimination diet and maintain/develop a healthy relationship with food along the way. If any of this interests you, here’s an application for a complimentary call.

Scientific References:

  1. Popescu F. D. (2015). Cross-reactivity between aeroallergens and food allergens. World journal of methodology, 5(2), 31–50.
  2. Tuck, C. J., Biesiekierski, J. R., Schmid-Grendelmeier, P., & Pohl, D. (2019). Food Intolerances. Nutrients, 11(7), 1684.
  3. Lim HS, Kim SK, Hong SJ.   Food Elimination Diet and Nutritional Deficiency in Patients with Inflammatory Bowel Disease.  Clin Nutr Res. 2018 Jan;7(1):48-55
  4. Parikh, R., Mathai, A., Parikh, S., Chandra Sekhar, G., & Thomas, R. (2008). Understanding and using sensitivity, specificity and predictive values. Indian journal of ophthalmology, 56(1), 45–50.
  5. Birch K, Pearson-Shaver AL. Allergy Testing. [Updated 2019 Feb 16]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from:
  6. Calvani, M., Bianchi, A., Reginelli, C., Peresso, M., & Testa, A. (2019). Oral Food Challenge. Medicina (Kaunas, Lithuania), 55(10), 651.
  7. Rezaie, Ali MD, MSc, FRCP(C)1; Buresi, Michelle MD2; Lembo, Anthony MD3; Lin, Henry MD4; McCallum, Richard MD5; Rao, Satish MD6; Schmulson, Max MD7; Valdovinos, Miguel MD8; Zakko, Salam MD9; Pimentel, Mark MD, FRCP(C)1 on behalf of The North American Consensus group on hydrogen and methane-based breath testing Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus, American Journal of Gastroenterology: May 2017 - Volume 112 - Issue 5 - p 775-784 doi: 10.1038/ajg.2017.46
  8. National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Food and Nutrition Board; Committee on Food Allergies: Global Burden, Causes, Treatment, Prevention, and Public Policy; Oria MP, Stallings VA, editors. Finding a Path to Safety in Food Allergy: Assessment of the Global Burden, Causes, Prevention, Management, and Public Policy. Washington (DC): National Academies Press (US); 2016 Nov 30. 4, Assessments, Diagnostic Testing, Disease Monitoring, and Prognosis.
  9. Mullin GE, Swift KM, Lipski L, et al. Testing for food reactions: the good, the bad, and the ugly. Nutr Clin Pract. 2010;25(2):192-198.
  10. Lomangino, K. (2013). Clinical Nutrition INSIGHT. Clinical Nutrition INSIGHT, 39(10), 10-11. doi:10.1097/01.nmd.0000436114.74157.6e
  12. Patenaude, Jan & Bright, D. (2009). Clinical Improvement of IBS, Migraine, Fibromyalgia and Arthritis Using Elimination Diets Based on Mediator Release Blood Testing. Journal of The American Dietetic Association - J AMER DIET ASSN. 109. 10.1016/j.jada.2009.06.092.
  13. Atkinson, W., Sheldon, T. A., Shaath, N., & Whorwell, P. J. (2004). Food elimination based on IgG antibodies in irritable bowel syndrome: a randomised controlled trial. Gut, 53(10), 1459–1464.
  14. Tomicić, S., Norrman, G., Fälth-Magnusson, K., Jenmalm, M. C., Devenney, I., & Böttcher, M. F. (2009). High levels of IgG4 antibodies to foods during infancy are associated with tolerance to corresponding foods later in life. Pediatric allergy and immunology : official publication of the European Society of Pediatric Allergy and Immunology, 20(1), 35–41.
  15. Innovative at-home Health Testing. (n.d.). Retrieved June 18, 2020, from
  16. Pinnertest Food Sensitivity Test. (n.d.). Retrieved June 18, 2020, from

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