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Food Sensitivities: What, Why, and How

October 6, 2025 | 27 Comments | SAFM Team

(This is a sample entry from the SAFM Q&A Treasure Chest, a tool with hundreds of entries to support students with their client needs. Students get unlimited access as part of SAFM’s functional medicine training program.)

Student Question:

Hi Tracy!

I have a new client – a  46-year-old lady who is literally allergic/sensitive to every good edible food, it seems!

Her doctor did an ELISA Basic Food Panel, and there is nothing for her to eat!  I have no idea what to do.  She’s frustrated and lost. Can you help me in any way? There are three panels with Low, Moderate and Avoid results. Now, if she is ‘sensitive’ to foods, wouldn’t they also irritate her? She has a few foods in LOW, but they are not foods she enjoys or can even ‘stomach’, such as fish, due to their strong smell. Surprisingly, she had no intolerance to all the sugars, corn starch, and MSG (at least on this test)!  What am I missing?

SAFM’s Answer:

Great question!  First of all, be sure to confirm what type of testing was performed.  For purposes of this reply, let’s assume this was a Total IgG food antibody panel, which measures Type 3 hypersensitivity and a specific type of adaptive immune reaction to foods.  Essentially, the test is measuring when the immune system is reacting to a consumed (and perhaps quite healthy!) food with hypervigilance.  Important information, but one that is not as targeted as we might assume.

First of all, it’s important to realize that no single food allergy/sensitivity/intolerance panel is going to yield a comprehensive and fully accurate list of all foods that might be causing inflammation and/or discomfort in your clients.  IgG antibodies are only one type of reaction that the body can have to a perceived threat (e.g. a food).  We can also have an IgA-mediated response (which happens in the mucous membranes of the body, such as the intestinal lining).  Similarly, someone may have an outright (even violent) allergy to a food and thus generate significant IgE antibodies in reaction to that food, but there may be no IgG or IgA antibody generation.

Food intolerances such as lactose or fructose intolerance are not reactions from the immune system at all, but your client will still suffer from consuming these foods.  The body can also react to lectins, mycotoxins, chemical additives, and other triggers in food that will not show up on a typical food antibody panel.  Going back to Total IgG measurements, that top note we can have high levels of these antibodies simply due to high consumption, and there may be little/no complement activation to trigger an inflammatory response.  Bottom line: this complexity can make it hard to “nail down” food sensitivities/allergies clearly via a lab test.  And it’s one of the reasons why the “gold standard” of identification of these issues is through 100% food elimination followed by a structured reintroduction challenge.

Sure, testing can be helpful!  But only as one puzzle piece.  Best-in-class food sensitivity testing depends on a unique person’s challenges….

  • A combination of IgG and IgA antibody testing can be especially helpful if there is gut-related dysfunction/disease (e.g. IBD). This becomes more valuable if an assessment of complement is added to ensure that a notable antibody response is actually promoting inflammation (to weed out false positives that all Total IgG testing is otherwise quite vulnerable to).  Cyrex offers a combined IgG/IgA panel and also makes the provision to ensure foods are tested in the form in which they are usually consumed (i.e. cooked vs. raw chicken and raw vs. cooked banana).  Vibrant Wellness offers a series of test panels that can be combined to assess both IgG and IgA alongside complement, a powerful combination. However, these tests can be quite expensive and thus not as accessible to many.
  • IgG antibody testing along with complement is another solid option where there is systemic inflammation. KBMO offers this testing along with multiple antibody markers of gut barrier function loss- a unique and valuable addition for gauging enhanced intestinal permeability, especially in the context of autoimmune dynamics.  This one is notably less expensive but still a sizable investment.
  • Mediator Release Testing (MRT) is designed to assess the body’s aggregate immune system response to a food by measuring the volume of overall inflammatory mediator response to it.  This is non-antibody testing.  A small, passionate subset of functional practitioners use these panels; many others question the lack of clinical study validating reproducible results or the scientific validity of using this overall type of testing (and isolating the effects of food from other factors).  Indeed, prior study shows a concerning, lack of reproducible results. More peer-reviewed studies of its reliability would be helpful.

For patients who cannot afford the above, there are also high-quality Total IgG panels (again, more vulnerable to false positives, so there will likely be more findings) from several functional lab companies such as Genova Diagnostics. However, the point above is key here: none of these tests is fully comprehensive for all symptom-promoting reactions to foods.  There is no such thing.  The body has MANY ways in which it can react negatively to foods, including mechanisms that don’t involve antibodies or measurable immune reactivity.  Testing can be valuable for some clients but is not always necessary.  Many times, clients are already aware of the most likely culprits, and you can help them with using that intuition in a structured, valuable trial. Again, the gold standard is food elimination and structured reintroduction.

But back to your client!  Typically, the best way to resolve the effect of the severe IgG-mediated food sensitivities is to eliminate them for a time.  Not just reduce it.  But rather 100% eliminate it – “cold turkey” – for a time to allow IgG antibodies to disappear and then reintroduce the food.  She likely needs to eliminate all the Severe and Moderate sensitivities 100% for at least 3-4 months initially (perhaps longer but this is a good starting point).  The “Low” foods are likely fine for her to continue to eat occasionally (1-2x/week) but not every day, so be sure to have her look through the list carefully and decide what foods need more rotation.   The good news is that if she can eliminate her most severe sensitivities fully (*and* prioritize calming the immune system and healing any enhanced intestinal permeability in the interim), there is a good chance she will be able to reintroduce all or nearly all of them with no effects after a few months (and thus be able to add them back into her diet).

Consider a 4-month elimination because it usually takes the client a few weeks to fully eliminate them (and officially “start the clock”) and get in a true 3 months of full elimination which, given the average half-life of IgG antibodies, will reduce their level to <10% of their original amount.  Of course, during those precious three months, we must, must also work on addressing the root causes of the immune hypervigilance!  Assess and explore sleep, movement, insufficient nutrients (especially Vitamins D and A and zinc), stress, toxic exposure/overload, microbiome imbalance, and enhanced intestinal permeability.  We must shift the environment overall – the terrain – that our immune and nervous systems are responding to if we wish them to have a more tolerant response to our foods.   Just eliminating the foods is not enough!

Your opportunity is to help her creatively to find alternative, healthy foods that she can use to nourish herself over the next few months.  Reassure her that this is not “forever” – just for a healing window.  If she feels she cannot eliminate all the Severe and Moderate foods right away, then start with all the Severe items (or a subset of them), at least as a starting points.  Some clients needs a little time to develop new habits/choices and progressively move into the full elimination. For sure, they need direct and detailed guidance from you on how to apply this intervention to their life… e.g., what to eat instead, how to find and prepare new foods, and how to incorporate new options into meals that their entire family can enjoy.

Keep in mind that the development of a sensitivity is not an indication in any way of the “healthiness” (or toxicity) of a food – just a measure of her unique immune system’s response to it.  And she may feel uncomfortable after eating some low-IgG-ranked foods due to maldigestion vs. due to any type of immune response.

If she has many Severe category foods and most of them are foods she eats often, then it’s likely that she has Enhanced Intestinal Permeability (EIP – again, a test like KBMO can assess this), a situation in which the immune system has extended exposure to semi-digested food in the gut lining (our “GALT”, gut-associated lymphoid tissue).  Obviously the immune system is going to react to this event with alarm; partially-digested food can become immunogenic on the wrong side of the intestinal “fence”!   Unfortunately, enhanced intestinal permeability is not rare given our cultural bias toward large use of antibiotics, over-the-counter painkillers, Vitamin D deficiency, chemically-laden foods, and chronic stress – all potentially damaging to the gut mucosa and barrier function.  In the case of EIP, people tend to develop sensitivities to the foods they consume most often (simply due to more frequent exposure).

It’s important to heal the excessive permeability while eliminating the foods, or an individual is likely to develop a follow-on set of sensitivities to the new foods they are choosing (alas, we see this often, especially in those with poly-autoimmune disease – a frustrating cycle).  After she begins eliminating the foods fully, consider all of the following, important steps:

  • take 3 grams of L-glutamine twice daily on an empty stomach to help heal the villi junctions in her small intestines (e.g. Metagenics “Glutagenics” or Designs for Health “G.I. Revive”), which also feature a number of other mucilaginous herbal agents that can help to heal the gut lining, e.g. slippery elm and aloe.  In some cases (~5%), taking l-glutamine can increase anxiety or irritability in very sensitive patients, so be on the lookout for this just in case.  Quercetin is also valuable for this purpose (e.g. 500mg, 1-2x daily).
  • check her vitamin D and ensure it is 40-60 ng/ml  (inadequate Vitamin D promotes the formation of loose junctions in the intestinal lining).  If not, supplement with Vitamin D3 to raise it (starting with 1000-2000 IU/day and progressively increasing as needed), but be sure to replete magnesium first, as it is needed to convert Vitamin D to its final form.
  • take a daily probiotic to help calm and balance her immune system with higher levels of T regulatory cells (e.g. Lactobacillus rhamnosus or L. plantarum).
  • avoid eating gluten entirely (even if it’s not on her sensitivity list).  In some people, especially those prone to chronic autoimmune disease, gluten can promote increased intestinal permeability through increased secretion of a protein called zonulin.
  • avoid all alcohol
  • avoid taking anti-inflammatory NSAID medications (e.g. Advil, Aleve), as these over time promote erosive damage to the protective mucosal lining of the intestines.

After she has fully eliminated a food 100% for at least 3 full months, she can do a “reintroduction challenge” of one food at a time.  Let’s say one of her sensitivities is to broccoli.  While continuing to eliminate all other sensitivities, she can “challenge” her immune system with broccoli by consuming a normally-sized serving twice during the day for three days in a row (a real serving, e.g. 1/2 cup broccoli, not just a bite).  Then stop. Encourage her to pay careful attention to any inflammatory response from her body during those 3 days and also 2-3 days afterward.  Symptoms may include reactions like headache, acid reflux, strong fatigue, brain fog, eczema, skin rash or acne, GI bloating, aching joints, sustained nasal congestion (or post nasal drip with clearing of throat).  If there is no reaction, then she is likely fine to resume eating that food (in a well-balanced diet).  Take a few-day break in between each new food challenge, and, importantly, only challenge one food at a time.  With this approach, most foods can now be tolerated.  However, there is often a food or two that requires a further elimination (for a total of  6-7 months).  Occasionally, there will be a food that simply cannot be successfully reintroduced, even after a year of elimination; these are likely permanent sensitivities that simply need to be avoided long-term.

If there is chronic autoimmune disease, care should be taken to ensure gut barrier function restoration, rebalancing of immune regulation, and reduction in autoimmune antibodies before reintroduction. Foods that are promoting EIP in a unique person (e.g. wheat or other grains) may need to be eliminated long-term to allow progressive and sustainable resolution of the autoimmune dynamic. This topic is addressed in great depth in our Level 2 Functional Medicine program courses Disease 202: Autoimmune Interconnectedness and  Immune Function, Loss of Tolerance, and Hypervigilance.

 

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27 Questions for “Food Sensitivities: What, Why, and How”

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  1. 13
    Melissa Heffron says:
    April 7, 2024 at 7:11 am

    1) If someone messes up and has a small amount of an IgG food sensitivity near the end of their 4 week elimination do they have to start over with every food? 2) Do you still suggest 3-4 month elimination vs 4-6 weeks? Thank you!

    Reply
    • 13.1
      SAFM Team says:
      April 13, 2024 at 11:39 am

      Yes, we suggest 3-4 months of 100% elimination of foods that invoked positive IgG4 response. This is because the half-life of an IgG is about 21-30 days, and by avoiding food for 3-4 months, we give the body a chance to bring down the IgG response below 10% and thereby significantly reduce the inflammation and allow for the gut mucosal lining to heal. That being said, this is not “a perfect science,” so the messed up situation needs to be regarded on an individual basis: which food was it? how strong was the IgG response on the test? what is the overall state of the client? did they have any adverse reaction form the tiny amount? – those are all important questions to consider when deciding whether or not to restart the elimination clock.

      Reply
  2. 12
    Melissa Heffron says:
    July 4, 2023 at 8:48 pm

    Do you have any articles/sources that point to why gluten/dairy are such common sensitivities?

    Reply
  3. 11
    hannah gunnison says:
    July 16, 2022 at 8:39 pm

    I have a patient with MS who is on an immunosuppressant. Is it worth doing a food sensitivity test (Cyrex Array 12) or will the results be inadequate due to the immunosuppressant?

    Reply
    • 11.1
      SAFM Team says:
      July 20, 2022 at 6:31 am

      The results of the IgG panel you are asking about are likely to be affected by the immunosuppressant. To which extent depends on the type of the immunosuppressant and how long the person has been on it. In light of that, one can still run a food sensitivity panel, keeping in mind that even the lowest reactions on the test results may be significant for this particular patient. Of note, Cyrex Array 12 is a Pathogen Associated immune Reactivity Screen, so if you are interested in food sensitivities, you may want to choose Array 10.

      Reply
  4. 10
    Bri says:
    June 28, 2022 at 3:31 pm

    is there any utility to rechecking IgG food sensitivity testing after a prolonged period of elimination?

    Reply
    • 10.1
      SAFM Team says:
      July 4, 2022 at 9:31 am

      Typically there is no need for rechecking the IgG levels to eliminate food if the elimination was done properly, the gut issues that created the food sensitivity got addressed and there is no adverse reaction upon the reintroduction. If the issues persist, something didn’t get addressed properly and one needs to go back to look at the interconnectedness of symptoms to check where there may still be an issue that is holding back the healing process. Very often, adrenal dysregulation or thyroid hormone issues are at the root of persistent food sensitivities.

      Reply
  5. 9
    Kathleen says:
    February 16, 2021 at 7:44 am

    I know that the elimination diet is the most accurate way to see how someone responds. However, in the back of my mind, I always have this nagging voice from having read a number of times that removing gluten and then bringing it back in can have some serious consequences especially for someone with unknown celiac. How do I navigate around this situation, even if I have a good HH and remove gluten without the concern of there being a liability? Thanks:)

    Reply
    • 9.1
      SAFM Team says:
      March 9, 2021 at 7:45 pm

      It depends. As always, you will want to assess and respond to each client’s unique situation vs. having a standard one-size-fits-all approach. If a person eliminates a common inflammatory culprit like gluten and experiences some dramatic improvements in debilitating symptoms, my clinical experience is that they never want to reintroduce it. They are grateful for and committed to the new possibilities in life they have discovered without it! I do not at all support the related idea of having someone purposefully consume gluten in order to see if it damages their intestinal lining enough or causes a sugar in inflammation and antibodies in order to be diagnosable. If a person eliminates one of the known, major allergens/sensitivities and experiences notably improvement, then the best course forward is often sustained elimination. If, however, a person develops a sensitivity to an everyday, typically nonallergenic, healthy food due to enhanced intestinal permeability (e.g. broccoli) and they wish to do a reintroduction trial after a sustained elimination, there is little risk of a highly debilitating result. We should, however, always caution clients that a reintroduction of a food that the immune system is still reactive to will indeed cause symptoms – perhaps a resurgence of what they suffered from before or perhaps something totally different. In the end, of course, the client must make and be responsible for the decision to reintroduce any foods. This is an example of the practitioner providing insight and guidance but keeping the client as the owner of their personal health.

      Reply
  6. 8
    Nazish Chagla says:
    February 3, 2021 at 11:44 pm

    Is L-glutamine not advisable for someone who has previously had cancer?

    Reply
    • 8.1
      SAFM Team says:
      March 11, 2021 at 4:01 pm

      Nazish – since you are an SAFM student, we will direct you to a write-up about this in the Documents section of the Disease Begins in the Gut 101 course page called “Glutamine and Cancer”.

      Reply
  7. 7
    deb says:
    January 28, 2021 at 10:08 am

    My ND uses the EAV system to help diagnose food sensitivities along with determining health problems.
    I would be interested in any additional literature you can share on this subject. Thank you!

    Reply
  8. 6
    Anu Ramesh says:
    September 2, 2020 at 9:17 am

    This question is regarding Liver and gall bladder supplements. When someone is having biliary symptoms like indigestion and dyspepsia – What would you recommend to improve bile secretion? I am debating Milk Thistle vs Chanca piedra. Liver With regards to detox some people say colon detox before liver – But you mentioned that insufficient bile is a cause of constipation. Since they are so linked together – I am confused about which one to give first.

    Reply
    • 6.1
      SAFM Team says:
      September 10, 2020 at 3:33 pm

      First, let’s not forget that indigestion and dyspepsia can be also caused by low levels of stomach acid and/or low pancreatic digestive enzymes output, or by dysbiosis, or simply by poor eating hygiene.
      If it is a biliary issue then the question is whether the bile production quality or flow or both are at stake and you’d support those in a slightly different way. There’s an existing post on the gall bladder rescue that speaks to the benefits of D-limonene to improve bile flow:
      https://schoolafm.com/ws_clinical_know/gallbladder-rescue/
      In terms of the bile production quality, one needs to ensure proper liver (and thyroid) function and this can be supported via diet with and specific cholagogue herbs, such as artichoke leaf extract, aloe vera, ginger, dandelion, and milk thistle to name a few. As for Chanca Piedra (Phyllanthus niruri L.), there is more research on its benefits for the liver. You may be interested in this article:
      https://pubmed.ncbi.nlm.nih.gov/31940365/
      I’m not sure what you mean by ‘colon detox’, but you certainly want to ensure regular and easy bowel movements before trying to upregulate liver detoxification pathways. We have a whole separate deep-dive clinical course on this topic if you are interested.
      https://pubmed.ncbi.nlm.nih.gov/31940365/

      Reply
  9. 5
    Miriam Zimela says:
    November 24, 2018 at 12:29 pm

    I have been ordering gluten sensitivity antibody test for my patients and the result has been showing level of transglutaminase IgA, and IGG that are not high enough. What does this indicate with regard to gluten sensitivity?

    Reply
    • 5.1
      SAFM Team says:
      December 18, 2018 at 11:19 am

      First, keep in mind is that in order for these antibodies to be detected, a person has to be eating gluten-containing foods. If they have been avoiding those for a while the antibodies will not come up high. If a person is consuming gluten-containing foods AND the antibody tests come back lowish I’d consider the following:
      1) There are many situations in which people’s overall IgG and IgA antibodies are not high enough and this is the reason why the results come back low. The reasons for low antibody levels could be:
      – allergy medication or on the steroid medication – both mimic the cortisol and can result in the immune suppression.
      – low immune function due to lack of nutrients (think low Vit D and A, zinc, etc.)
      – low thyroid function (gut issues; toxicity; estrogen dominance)
      – low adrenal function (chronic stress of any origin)
      As you can see these issues are quite ubiquitous and potentially affect a large portion of the population.

      2) Please note that the transglutaminase IgA gets elevated primarily in the gut mucosa and may not be reflected in the blood. In addition to this test you may consider testing for the Endomysial antibody (EMA test) which is another marker to determine gluten sensitivity. This review goes in depth into the differences between the transglutaminase and the endomysial antibodies:
      https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4003135/
      https://pmj.bmj.com/content/76/898/466

      3) No test is perfect, even if the results come back ambiguous and a person still suffers negative symptoms when consuming gluten it is an obvious sign of sensitivity to that food, so the elimination diet can be very helpful.

      4) Some people choose to undergo an endoscopy to determine the extent of gut damage, however, there also could be no gut damage but gluten/wheat sensitivity that causes an inflammatory response in a client. This is another great opportunity for the elimination diet.

      Reply
  10. 4
    SAFM Team says:
    October 29, 2018 at 8:45 pm

    Since you have already seen this post, you might also appreciate this one: https://schoolafm.com/ws_clinical_know/can-you-spot-histamine-intolerance/ . It is a not a “food sensitivity” but rather an intolerance, closer to the concept of lactose intolerance. A person may wrestle with histamine intolerance for rich variety of reasons. If they don’t have sufficient enzymes/microbes in the gut to have optimal levels of DAO enzyme to break down histamine, then they can be overloaded simply by histamine naturally present in foods. However, one can also have histamine intolerance because there is a dynamic *internal* to the body driving strong synthesis of histamine, and the body’s methylation capability is unable to keep up. The half-life of IgG antibodies is about 21 days.

    Reply
  11. 3
    Tammy Valta says:
    September 27, 2018 at 10:01 am

    What would be a good probiotic for a woman with gluten intolerance (she gets bloated every time she has wheat and experiences acid reflux as well)? She is also taking an antidepressant, was 10 years on metformin and Glucophage, and is still quite overweight. Thank you.

    Reply
  12. 2
    sharon chud says:
    November 22, 2017 at 4:59 pm

    After a 10 day use of an antibiotic for a sinus infection what would you recommend to replace the intestinal flora? Should I replenish the flora first or go right into no probiotics to prepare for the SIBO test?

    Reply
    • 2.1
      SAFM Team says:
      December 8, 2017 at 4:01 pm

      Generally, it is best to begin taking a probiotic in advance of starting an antibiotic course – to help prime and balance the immune system reaction. I usually recommend a Lacto/Bifido blend that also includes S. Boulardi e.g. Metagenics UltraFlora Acute Care, starting asap before the antibiotic course, continuing through it, and then extending for another ~6 weeks. Keep in mind that your antibiotic use has undoubtedly dramatically affected whatever SIBO was present; the overgrowth may or may not still be present and likely cannot be accurately assessed for quite a while. It may be quite logical, instead, to just support the gut’s recovery with the probiotic, focus on optimizing eating hygiene (e.g. no grazing) and digestion (e.g. chewing!), optimizing diet and immune system function, and seeing over the next several weeks if SIBO is actually still a part of your life or not. Future testing may not even be necessary.

      Reply
  13. 1
    Kathleen says:
    April 17, 2017 at 10:02 am

    Hi Tracy,
    I know we always talk about IgG in terms of food sensitivities but what about someone that is IgG deficient? I am trying to support a man that is deficient and his immune weak and was given injections for years with globulins but no longer receiving them. Thanks, I just don’t think of it from this angle.

    Reply
    • 1.1
      SAFM Team says:
      April 23, 2017 at 2:27 pm

      Total IgG level can be measured in blood. If an immune system is calm and at rest, their overall IgG levels will be moderate, an indication that the immune system is well-primed. One can end up with low levels due to persistent immune challenge (e.g. Lyme disease, EBV) or genetic factors. Indeed, someone may have food sensitivities but with very low levels of IgG, and their lab sample may not trip the threshold of significance to show up on a test. A great reminder that there are limitations to any and all labwork markers. In terms of boosting adaptive immune function to support a lower IgG level, I would consider the importance of optimizing immunity nutrition (e.g. D, A, Zn), stress relief, ample deep sleep, and ensuring a healthy microbiome. I would also consider regular use of colostrum as a supportive supplement (or if need to be dairy-free e.g. https://www.xymogen.com/formulas/products/452 ).

      Reply
      • …
        Jodi Franklin says:
        April 25, 2017 at 10:12 am

        If someone takes an IgG food sensitivity panel, such as the Food-Safe Allergy Test, and it shows no sensitivities, but the client has an autoimmune disease (I have had three clients show no sensitivities, but one had Colitis and the other two have Vitiligo), does that mean they could still be having IgG reactions to food, but it’s just not showing up doe to immune system challenges/genetic factors? If so, is there any test that can better identify these reactions?

        Reply
        • …
          SAFM Team says:
          April 30, 2017 at 1:19 pm

          There are several scenarios potentially at play. First of all, a client may have suppressed ability to form immunoglobulins – either innately or due to drugs; this is often the case with AI patients as immunosuppressant drugs they are typically using to control the disease will suppress immunoglobulin synthesis by definition and make food sensitivity testing a waste of time. Even if there are no steroidal or immunosuppressant drugs at play, be sure that their globulin level is at least mid-normal (in RR) as a rough check. They may also have food sensitivities that are not driven by IgG reactions (perhaps IgA, such as the case in celiac disease), and they may have sensitivities not driven by the adaptive immune system at all. As I note in the article below, there is no such thing as a “comprehensive” food sensitivity test. Just keep in mind that the choice to recommend an AI patient fully eliminate gluten – and perhaps dairy and all grains – is much more about preventing more intestinal permeability via more zonulin release (which is not an antibody-driven issue) than it is about food sensitivities. These are two separate issues. As I said above, I believe the current best (though quite expensive) test for food sensitivities is the Cyrex array # 10.

          Reply
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