Food Intolerance vs. Food Allergy

Let’s start with this:  food allergy and food intolerance are NOT the same thing.

If you are concerned you may have a food allergy or are experiencing food intolerance, discuss your concerns with your medical doctor for a proper work up and treatment.

Food allergy is an abnormal immune response to a food protein and can occur via immunoglobulin E (IgE), non IgE or mixed IgE/non-IgE mechanisms. Clinical entities of food allergy include IgE mediated food allergies, eosinophilic esophagitis and food protein-induced enterocolitis syndrome (FPIES). Food allergy occurs in about 1-2 % of adults and less than 10% of children.(1). The most common IgE mediated food allergies include: peanut, tree nut, milk, egg, wheat, soy, fish and shellfish. The allergic reaction can involve the skin, mouth, eyes, lungs, heart, gut and brain.(2)

Food allergy reactions can be mild or severe, including anaphylaxis, which can be life threatening. Anaphylaxis occurs quickly after the exposure to the allergen. Anaphylactic symptoms may include: shortness of breath, nausea, vomiting, hives, swelling of lips and tongue, low blood pressure, wheezing, fainting, and cardiac arrest. Anaphylaxis involves the whole body and requires immediate medical attention (i.e. call 911).

If you are at risk for anaphylaxis, your allergist will prescribe a self injectable epinephrine pen and instructions on how to use it.

Certainly, one can experience food allergies and food intolerances. In IBS, however, food intolerance is much more common than food allergy. About 2/3 of individuals with IBS report food related gut symptoms.(3) Food intolerances occurs in about 20% of the global population (1).  Food intolerance may occur due to enzymatic defects. For example, a decline in lactase enzyme production may lead to lactose (the sugar in milk) intolerance. A reduction in the enzyme complex, sucrase isomaltase can result in intolerance to sugar and possibly starch rich foods. Histamine intolerance is yet another potential food intolerance resulting from a decline in diamine oxidase, an enzyme produced in the small intestine that helps degrade dietary histamine. FODMAP intolerance is common in IBS, with about 50-80% of those with IBS noting adequate symptom relief with a low FODMAP diet.(1). For more on the low FODMAP diet, check out my FODMAPs 101 handout here.

Food intolerance can be life debilitating in some cases but unlike the potential with food allergy, food intolerance is not life threatening.

For a great primer on this topic of food allergy vs. food intolerance as it relates to individuals with functional gut disorders (such as irritable bowel syndrome), read the article titled, Food allergies 101 by gastroenterologist, Brian E. Lacy, PhD, MD, FACG featured in AGA perspectives, an opinion magazine of the American Gastroenterological Association, here. (4)

In brief, food intolerance is much more common in individuals with IBS than food allergy. That being said, there are a wide range of food intolerance/sensitivity tests marketed to those with IBS. These tests promise that they can accurately identify individual food intolerances. Unfortunately, there is no science based test available currently to accurately test food intolerances, outside of lactose intolerance.

I’ll say it again, for those in the back of the room…there is currently NO SCIENCE BASED test to diagnose a broad spectrum of food intolerances.

Today, I am grateful to share with you a brief interview I did with Dave Stukus, MD, a Board Certified Allergist and Assistant Professor of Pediatrics in the Section of Allergy/Immunology at Nationwide Children’s Hospital. Dr. Stukus serves as the Director of the Hospital’s Complex Asthma Clinic and is on the board of directors for the Asthma ad Allergy Foundation of America. In this interview, he provides some key points about food allergy testing and the real deal about food intolerance/sensitivity testing, including the commonly used IgG tests.

Here is my Q and A with Dr. Stukus.

Kate: Are there any evidence-based tests currently available to test food sensitivities or intolerances?

Dr. Stukus: There are no validated or evidence based tests for food sensitivity and we only have the hydrogen breath test for those who have lactose intolerance. The best way to determine if someone has a possible food sensitivity or intolerance is to take a detailed history of symptoms and suspected foods, consider whether that relationship is likely causative or more likely unrelated, then strictly eliminating that food(s) for 2-4 weeks followed by very careful objective assessment to see if all symptoms resolved, THEN reintroduction of those foods to see if symptoms return. A lot of vague or chronic symptoms are misattributed to being caused by ingestion of a specific food or ingredient – these are often unrelated or fail to hold up when elimination and reintroduction diets are pursued.

Kate: Can you describe what we know about IgG testing and its relationship with the foods you eat regularly?

Dr. Stukus: IgG is a protective antibody that serves as a marker of prior exposure and memory. We know from multiple food allergy immunotherapy studies that IgE is the allergy antibody involved in immediate onset hypersensitivity reactions and when people become desensitized, or less allergic, to foods, their IgE goes down and IgG goes up. This indicates that IgG is involved in the adaptive response to eating a food. In other words, it is normal and expected to produce IgG towards foods that we eat and tolerate – it’s our immune system’s way of saying “I know you”.

Kate: If you suspect you might have food allergies, what type of provider should you consult to help you determine this?

Dr. Stukus: Board certified allergists are the best type of specialist to determine if a food allergy is present. Allergists receive extra dedicated training after they finish their residency in pediatrics or internal medicine. They also receive focused training on the immune system, including normal and allergic responses. Allergists stay up to date on the rapidly changing evidence surrounding food allergy diagnosis and management and are best equipped to perform AND interpret testing properly.

Kate: Even food allergy testing is not perfect, right?  Can you describe the skin prick vs. serum IgE testing?

Dr. Stukus: Both skin prick and serum IgE testing evaluates for the presence of food specific IgE antibodies. Skin testing involves introducing very small amounts of the food protein to the allergy cells (mast cells) in the skin on the back or forearm. If a person has food specific IgE attached to their mast cells, they will recognize that food protein and open the cells to release histamine, which causes a very small and localized allergic response as detected by itching, redness, and a small bump in the skin. Serum IgE testing measures the amount of IgE in the blood. Both skin and serum IgE tests have high rates of falsely elevated results. Many people are sensitized to foods (they produce IgE) but are not allergic, meaning they eat the foods without rapid onset itching, hives, swelling, etc. There are many reasons why these tests cause high false positive results, including nonspecific binding to food proteins, cross reactivity with inhalant allergens such as pollen (people allergic to birch tree pollen often have false positive IgE tests to peanut), or they have very sensitive skin or multiple allergies.

The best test to determine if a food allergy is present is the clinical history of what happens when a food is ingested. There are no hidden food allergies. If you can eat a food without having any problems, you are not allergic to that food. In addition, food allergies will cause symptoms regardless of type of food, so if someone thinks they’re allergic to milk, they should not be able to eat cheese, yogurt, ice cream, etc. Oral food challenges are the gold standard test to determine if food allergy is present. There are too many physicians who order too many food allergy tests and then misinterpret false positives, which leads to way too many people avoiding foods they’re not actually allergic towards.

Lastly, skin and serum IgE tests do NOT diagnose food allergy. The size of the test result only indicates the likelihood that food allergy is present, which is really determined by the clinical history. Anyone who orders food allergy tests should be able to predict the result prior to testing. In addition, skin and serum IgE tests do NOT determine how severe an allergic reaction may be – there are no tests that determine severity. So, anyone who says “my allergy test says I’m deathly allergic to peanuts” has been misinformed.

Dr. Stukus had done a number of “tweets” via Twitter a while back sharing his experience with the home kits available to test food sensitivities. I asked him to share his experience.

Dr. Stukus: When I tested my own blood with one of the at home IgG food sensitivity tests, my results indicated that I was ‘sensitive’ to every single food tested, albeit to varying degrees. They included 80+ foods, including different types of cheese, which from an allergy/immunology standpoint makes no sense – milk protein is the same in cheeses, which differ based upon how they’re cultured. There was no unit of measurement provided for my levels and no normal range was provided. These are two enormous red flags. Lastly, my results indicated I was ‘highly sensitive’ to cashews, which I rarely, if ever eat. This gave me tremendous insight into the pseudoscience and marketing behind these tests. Essentially everyone who takes one of these tests will be told they have food sensitivities…because everyone will and should make IgG to foods! And of course, the companies don’t stop there – they suggest personalized counseling or other products, all of which cost $$$.

Well…if you are still here with me, thank you.  I am so grateful for Dr. Stukus’ time to share his expertise with all of you. It’s hard when you feel poorly, perceive food as a trigger to your symptoms and still feel you don’t have any answers. Unfortunately, there are health care providers and companies that are taking advantage of this opportunity to take YOUR money without any science to support the tests they are utilizing.

Stay informed. Choose your providers wisely.

References:

Tuck, CJ., et al Nutrients; 2019: 11(7): 1684.  Open access here.

https://www.kidswithfoodallergies.org/page/what-is-a-food-allergy.aspx accessed 12/10/19.

Bohn L, et al. Am J Gastroenterol. 2013;108: 634-641.

Food allergy 101 by Brian Lacey Open access here. http://agaperspectives.gastro.org/food-allergies-101.