What is a Food Allergy, and How do I Test for One?

Written by Dr. Currey

Food allergies are a pretty hot topic both in the naturopathic world and in conventional medicine, and if you are familiar with the subject, you know that there is quite a bit of controversy surrounding the term allergy.

To help you understand the different types of food allergy and sensitivity testing, first we need to talk about the different types of immune responses that can occur in the body and which ones can be measured through a laboratory test.


When we are talking about allergies, we are usually talking about the type of reaction where you break out in a rash or hives, your airways may start to close up, and if not treated promptly, you could die.  These are very serious, and it’s hard to not know about them if you have one.

A perfect example of a food allergy is the child who cannot be around peanuts and needs to carry an epi-pen.  These reactions are life threatening and not to be taken lightly.  The portion of the immune system responsible for this type of reaction is an antibody called IgE.  The levels of IgE can be measured in blood, and if you were a child with allergies, you may remember skin scratch tests and allergy shots as diagnosis and treatment for these reactions.  This is the type of immune reaction most commonly tested for in allergy clinics and by medical doctors.


There are other immune reactions besides the life-threatening IgE reaction.  Some of these can be measured through laboratory testing, and others can only be recognized through use of an elimination diet.

IgA – this antibody is mainly found in the digestive, urinary, and respiratory tracts.  It can be tested for in salivary, stool, and blood samples.  It is a first line antibody akin to the body’s bouncer as it is found in the body’s entryways.  This antibody can easily be depleted by chronic immune reactions leading to false negative lab results, so a total IgA level should always be used side by side with any specific IgA test.  This test is commonly done in the diagnostic workup of celiac disease – an intolerance to the protein gluten that is found in wheat and several other grains.

IgG – this antibody is responsible for delayed sensitivity reactions.  In this type of reaction, the immune response may not occur until several days after eating an offending food making the culprit harder to identify especially if it is a food one eats everyday.  In this case, a person might not be aware that they have a food intolerance/sensitivity and they might feel “normal”.  It isn’t until the responsible food has been identified and removed from the diet that a person realizes the full affect it had on them.

Non-measurable responses – The immune system is very complex and it’s reactions are driven by many, many different chemicals and blood cells named by mashes of numbers and letters.  At this point, no test has been developed that can test all aspects of the immune system.  Because of this, the only completely accurate and all encompassing test for reactions to food is an elimination diet followed by slow reintroduction of foods and careful analysis of symptoms.  This approach when done well can take over 6 months.  If someone really wants to get to the bottom of their symptoms and is ready to fully embark on an elimination diet, I applaud them and have many resources to help them on their path.

A key point of confusion: if you want to go on an elimination diet, you need to remove the food you are testing for 100%, we are trying to turn off the ongoing immune reaction and any exposure to that food will trigger that response if it it your offending food.  Cutting down on gluten is not an elimination diet.

Available tests:

In our office, when a person wants to investigate the possibility of food reactions and is not ready for an elimination diet, we have several options for testing IgA, IgE, and IgG responses.  We do not do skin scratch testing but will refer out to an allergy clinic for that procedure when indicated.   We can, however, send samples of blood, saliva, and stool out for testing through several different labs.  Currently, our favored laboratory for IgG and IgA testing in our office is USBioTek.  We encourage you to feel free to explore their different testing options through their website or schedule an appointment to go over them with us.  As always we are happy to help guide you through this process.

A final note and an analogy:

When I think of food allergy/intolerance/sensitivity, I picture a burning house full full of smoke.

In this analogy, your body is the burning house and the smoke is the array of symptoms you are experiencing.  When you seek medical care, you want to feel better and be healthier – you want to rebuild your house.  The problem is, if you start the rebuilding process (herbs, supplements, diet, etc) without putting out the fire, your efforts will only bring temporary relief.

The first priority must be to put out the fire, clear out the smoke, and fix any repairable damage that has occurred.

Many people comment that they never had a problem with a specific food until they tried to remove it from their diet. Some think that the removal triggered a reaction.  What has really happened is the “smoke” has been cleared out and your old “normal” doesn’t feel so normal anymore.  Living without the symptoms you have become accustom to makes them much more apparent when they resurface.

I hope this has been a helpful review and cleared up some of the more common misconceptions surrounding food allergies and intolerances/sensitivities.


  • House fire by dvs cc by 2.0, http://www.flickr.com/photos/dvs/3541139652/meta/
  • Us BioTek Laboratories, https://www.usbiotek.com/index.html
  • Vasquez, A. DC, ND, Integrative Rheumatology – Concepts, Perspecitves, Algorithms, and Protocols, OptimalHealthResearch.com 2007 Second Edition