June/July 2025 Issue
Staying Informed on Food Sensitivities
By Erica Golden, RDN, LD, IFNCP
Today’s Dietitian
Vol. 27 No. 6 P. 32
From Data to Clinical Practice
Modern wellness culture Is filled with discussions of food sensitivities. Terms like “allergy,” “sensitivity,” and “intolerance” are often incorrectly used interchangeably, and confusion among consumers about adverse food reactions is at an all-time high.
With increasing interest in and confusion about food sensitivities, it is vital for dietitians to be knowledgeable about adverse food reactions, the state of sensitivity testing, and how to identify and manage adverse food reactions when they do occur.
Food Allergies
To understand and identify food sensitivities, RDs must first understand what they are not. Food allergies and intolerances are often confused with food sensitivities. Food allergies tend to be the most dangerous of the adverse food reactions, though they are not always immediate or anaphylactic, as many assume.1
The “classic” food allergy is the immunoglobulin E (IgE)-mediated food allergy, such as is common with shellfish, peanut, tree nut, soy, or egg allergy. These reactions tend to present very quickly after exposure, and can be quite severe, with symptoms potentially including hives and anaphylactic shock.1
However, non-IgE-mediated food allergies are generally delayed and may not occur immediately after the food is consumed.1 Non-IgE-mediated allergic responses may include food protein-induced enterocolitis syndrome, which is suspected to be T-cell mediated,2 and celiac disease, which includes a T-cell-mediated hypersensitivity response to gluten.3 Additionally, there are food allergies that are considered “mixed,” sometimes IgE-mediated and sometimes not, such as cow’s milk protein allergy or eosinophilic esophagitis.4
Food Intolerances
Distinguishing food intolerances from sensitivities and allergies, intolerances are generally classified as nonimmune-mediated adverse food reactions. Some experts have proposed renaming food intolerances as “nonimmunological adverse reactions to food.”4 This means the symptoms that occur with the consumption of the food are related to lack or malfunction of an enzyme (such as the lactase enzyme) or pharmacological (such as a reaction to pharmacologically active substances in food like caffeine or histamine). Reactions are consistently dose dependent, meaning that higher intake of the substance leads to more severe symptoms.4
Food Sensitivities
Food sensitivities are the most difficult to define, as there is a lack of consensus on the definition and classification. A food sensitivity is typically defined as an idiosyncratic, individual-specific reaction to food, often with unknown or poorly defined mechanisms. Many practitioners and researchers consider food sensitivity to be an immune-mediated adverse food reaction, while others consider it to be “irritative,” but nonimmunologic.4,5 However, because identifying the mechanisms behind food sensitivities can be challenging, and because of the potential overlap between food allergies, food sensitivities, and food intolerances, immune involvement in each case is often difficult to determine.5
Symptoms of food sensitivities may include gastrointestinal symptoms, as well as systemic symptoms such as headache, fatigue, or skin reactions such as dermatitis. Symptoms can range from mild to severe but are generally not life-threatening, and are typically dose dependent.4,5
According to Kristen White, RDN, LDN, CLT, “One of the least well-understood aspects of food sensitivities is the delayed nature of symptom onset. Many individuals expect immediate reactions to problematic foods, but symptoms can manifest several days after consumption, making it challenging to associate specific foods with adverse effects. This delayed response often leads to misconceptions and difficulties in identifying true food sensitivities.” The duration of symptoms is also variable. Symptoms may be transient and disappear quickly or may persist for a long time even after elimination of the trigger food.5
Some commonly self-reported food sensitivities include wheat (or gluten), dairy (or casein), soy, and food additives.5
Mechanisms of Food Sensitivity
While underlying causes of food sensitivity symptoms are often unclear, multiple theoretical mechanisms exist. Food sensitivities may be immune-mediated, with immune system involvement potentially including mediator release, complement activation, and immunoglobulins, with some non-IgE-mediated food hypersensitivity reactions possible.5 At the same time, food sensitivities likely overlap with nonimmune mechanisms like food intolerance, including FODMAP intolerance, and the nocebo effect.6,7 Intestinal barrier dysfunction, exorphins, dysbiosis, and inflammation also may play roles in the presentation of symptoms of food sensitivity. 5,8-10
At one end of the spectrum are individuals who have self-reported mild food sensitivities without perceivable immune reactions. On the other end of the spectrum may be significant and measurable immune activation, inflammation, and severe symptoms. While there is evidence supporting an increase in certain immune markers in food sensitivity, such as increased levels of certain T-cells and eosinophils in nonceliac gluten/wheat sensitivity,10 or a decrease in inflammatory markers in patients with rheumatoid arthritis after following a gluten-free diet for three to 12 months,11 the true extent of immune involvement in food sensitivity remains unknown.
For example, some evidence supports the role of IgG antibodies in predicting migraine headaches in response to food sensitivities.12 On the other hand, individuals undergoing immunotherapy for allergens also show increasing levels of IgG antibodies concurrently with decreasing levels of IgE antibodies, suggesting that IgG levels may simply be linked with tolerance to a potential allergen.13 This seemingly conflicting data still requires further investigation.
There is much diversity of opinion among dietitians in this space, as well. “A food sensitivity isn’t usually about the food—it’s typically about a dysregulated immune system of the gut,” says Heidi Turner, MS, RDN, CHLC. “The key thing as the practitioner is to determine what is driving the immune system to react to the foods [they are] eating.” Turner finds in her practice that high amounts of emotional or physical stress, a diet high in ultraprocessed foods, poor self-care habits, nutrient deficiencies, and gastrointestinal diseases like IBD or gastritis are often underlying factors in food sensitivity. She works toward the goal of eventually expanding the client’s diet as much as possible, once these underlying factors are improved.
Other nutrition professionals feel that food sensitivities are innate. “Food sensitivity is in the person,” Joan Breakey, APD (Australia), notes, based on her research and clinical experience. “If you are food sensitive, your symptoms may change as your life progresses. The level of strictness may change such that diet had to be very strict in infancy, then tolerance improved in childhood, but deteriorated in your teens, improved again in adulthood, but unexpectedly deteriorated again in mid or later life. This is quite normal in food sensitive people.”
The Nocebo Effect
The nocebo effect is essentially the placebo effect in reverse: if an individual has negative expectations about the outcome of a treatment, their expectations may help to fuel that negative outcome.7
Some recent research on nonceliac gluten/wheat sensitivity suggests that the nocebo effect may have a potential additive effect on food sensitivity. The combination of expecting to consume gluten and actually consuming gluten (their self-reported trigger food) had a bigger effect on symptoms than unknowingly consuming gluten, or than expecting to consume gluten without actually consuming gluten.7,14
Issues Commonly Confused With Food Sensitivity
When a food sensitivity is suspected based on a client’s symptoms, history, and diet recall, it is vital to start by evaluating other medical conditions. For example, has celiac disease already been ruled out? Have they ever been evaluated for food allergies, and if not, do they have symptoms suggestive of either IgE-mediated or non-IgE-mediated food allergies? If the symptoms are largely gastrointestinal in nature, has the client been evaluated by a gastroenterologist for inflammatory bowel disease and irritable bowel syndrome? While food sensitivities may still play a part in these cases, it’s important to consider the full picture.
If the symptoms are primarily gastrointestinal, the potential presence of food intolerance, such as lactase deficiency or sucrase-isomaltase deficiency, should be considered as well.
Additionally, dietitians should consider whether clients have ever been diagnosed with an eating disorder or whether they need further evaluation by a mental health professional. Conducting screening for disordered eating patterns—including avoidant/restrictive food intake disorder, orthorexia, anorexia nervosa, and binge eating disorder—is of utmost importance whenever a restrictive elimination diet is in view.
Food Sensitivity Testing
Many patients and clinicians are searching for tests that may be able to reveal underlying food sensitivities, taking the guesswork out of elimination diets and providing simple (though typically not easy) solutions to their chronic symptoms.
It’s not hard to understand the appeal of these sorts of tests; however, the unfortunate reality is that they are generally expensive, under-researched, unreliable, and unvalidated. Even with IgE-type food allergies, where the mechanism is well-understood and testing appears to be clear cut, IgE-mediated allergy tests are still not considered conclusive, and the gold standard remains the oral food challenge.4
Since the causes of food sensitivity are potentially so diverse and so poorly understood, the testing landscape is even more problematic. A wide range of tests attempt to assess variables theoretically connected with food sensitivity. For example, iridology testing suggests that patterns in the iris reflect health conditions, including food intolerances. Electrodermal tests are supposed to detect changes in skin conductance, which are purportedly associated with food sensitivities. These tests are neither scientifically valid nor clinically useful.15
More common tests, however, include food-specific IgG blood testing, the mediator release test, and the antigen leukocyte antibody test. As previously mentioned, IgG blood testing is contested based on confusion about whether IgG levels actually measure sensitization to a food antigen or exposure and tolerance to it.13 The mediator release test and antigen leukocyte antibody test, on the other hand, don’t focus on immunoglobulins, but rather on the immune cells themselves and their reaction to food antigens in vitro. While some dietitians and health practitioners anecdotally report dramatic results from using these tests to guide elimination diets, the tests still require more unbiased, peer-reviewed research studies to demonstrate their validity.15
Elimination Diets for Food Sensitivity
Despite the challenges posed by the nocebo effect, the tailored elimination diet is generally considered the best and most reliable tool for identifying or confirming suspected food sensitivities at present. However, the elimination diet is not risk-free and should be attempted only after a detailed evaluation of the medical, including psychiatric, conditions detailed above, ensuring that the client will still be able to meet all their nutritional needs while on the elimination diet, and taking care to protect their relationship with food and avoid creating unnecessary and harmful food fears while on an elimination diet.16
Sensible dietary and lifestyle changes should also be implemented first. In some cases, standard advice such as evaluating meal timing, sleep hygiene, exercise tolerance, and other aspects of stress management, discussing portion sizes of foods that can trigger digestive distress in all individuals (such as foods that are high in fat or sugar alcohols), and decreasing intake of alcohol and caffeine can bring about substantial improvements in patients’ symptoms.
Preparing for an Elimination Diet
In preparation for an elimination diet, having the client keep a detailed food-symptom log can be helpful. While food sensitivity symptoms may be distanced from initial intake of the trigger food, over the course of several weeks of tracking, enlightening patterns may be identified.
If symptoms do seem to align with food sensitivity, elimination diets may be more straightforward to plan. However, challenges often arise when the causes of the adverse food reactions are unclear or the symptoms are chronic, when multiple culprits are suspected, or when the foods that seem to be the triggers are foundational to the client’s daily dietary pattern. Additional discussion, planning, and experimentation time may be necessary in these situations. A gradual transition period in which alternative foods are gradually added to allow the client time to get more comfortable with these replacements before eliminating the suspected trigger foods completely can be helpful.
Conducting an Elimination Diet
Elimination diets vary greatly in restrictiveness and complexity. Patients may need to eliminate only one food, such as eggs or gluten, or they may eliminate multiple foods at one time. The six-food elimination diet, which has been used most successfully in eosinophilic esophagitis (a mixed IgE-mediated and non-IgE-mediated allergic condition), eliminates the top allergenic food categories (dairy, eggs, wheat, soy, peanuts and tree nuts, and fish and shellfish).16
Food chemical elimination diets, such as the Feingold diet or the FAILSAFE diet, can be quite intensive because of the breadth of foods that must be eliminated, including not only processed foods and artificial food additives but also things like salicylates, amines, and glutamates, which are naturally present in many whole foods.17 Even more extreme is the few foods diet, which limits what foods can be consumed to just five to seven specific foods (for example, rice, lamb, venison, potatoes, bananas, apples, broccoli, and radishes, plus a multivitamin supplement).18
Rotation diets offer an attractive potential dietary strategy for identifying and managing suspected food sensitivity. There are several variations of rotation diets, but in general, these diets are based on the belief that foods eaten every day are more likely to cause symptoms than those that are eaten less frequently. These diets may be comparatively more inclusive than other elimination diets, attempting to maintain a wider variety of foods. Even foods with suspected sensitivity may be allowed on an intermittent schedule with lowered frequency and/or dose. Certain foods are eaten at the same meal and same day, and then the client will not eat those foods again until three or four days later.19 Additionally, carefully planned rotation diets may offer a strategy for creating a diverse and yet predictable pattern of food intake that may be conducive to improved clarity in identifying sensitivities overall.
Regardless of the type of elimination diet the client is following, dietitians should check in frequently to ensure nutritional adequacy, to check for eating concerns and anxiety surrounding food, and to offer support with specific nutrient-dense alternatives catered to the client’s preferences and needs as the process evolves.16
Suggested time frames for the elimination phase vary, but most professionals suggest four to eight weeks of exclusion before determining whether the elimination phase was effective in reducing the target symptoms, and moving on to challenging restricted foods one at a time, if indicated.16,18,19
After the challenges have been completed and documented, the RD and client can work together to create a longer-term diet plan. If it is feasible, appropriate, realistic, and in the interest of improved quality of life for the client to continue a diet free from the foods to which they have determined a sensitivity, then the RD can help them build a plan to meet their nutritional needs. However, altering the frequency of exposure and/or dose of some trigger foods may bring relief for some patients without needing to permanently remove the food(s) in question. Tolerance may also change over time, making it necessary to reevaluate previous conclusions and make ongoing adjustments as needed.20
It is also important to continue monitoring eating concerns, stress, and anxiety surrounding eating or meal planning, and symptoms of orthorexia.
Summary
Food sensitivities are poorly understood phenomena potentially arising from a variety of complex mechanisms, including immune as well as nonimmune mechanisms. Additionally, it’s important to consider other underlying medical—including psychiatric—factors that may be triggering the symptoms attributed to food sensitivity.
While many tests may attempt to pinpoint food sensitivities, most of the tests currently available are underresearched and cannot currently be widely recommended. Although the elimination diet has drawbacks, when it is done carefully with the support of a skilled RD, it may be much more reliable than many of the available testing options.
RDs should be well-versed in the potential symptoms and potential causes of food sensitivity so that they can educate their patients in a balanced way. Because these patients may have been dismissed by providers in the past, it is important to listen to their concerns and ask thoughtful questions.
Dietitians must also be clear about what we do and do not know about food sensitivities and adverse food reactions in general. Nutrition professionals should avoid oversimplifying by implying that IgE-mediated allergies or lactose intolerance are the only forms of adverse food reactions. On the other hand, they must avoid overstating by implying that the medical community knows much more about food sensitivity than is truly known at present. Providing balanced, conscientious, and empathetic care—along with a good dose of clinical humility—is essential.
— Erica Golden, RDN, LD, IFNCP, is a clinical dietitian, author, and speaker specializing in mental health and digestive disorders. In her private practice, Nourished Mind Nutrition, she uses integrative, trauma-informed care to support clients with depression, anxiety, irritable bowel syndrome, and disordered eating. Golden is the author of the continuing education book Nutrition and Mental Health: Integrative Approaches for Diet, Dysfunction, and the Gut-Brain Axis.
A Note About Supplement & Medication Tolerance
Patients who regularly take supplements and/or medications may need to work closely with an RD and primary care provider team who can help them properly assess to what degree these compounds may be contributing to any present intolerance symptoms. This is especially important for those who are taking larger quantities of either supplements or medications.
References
1. Lopez CM, Yarrarapu SNS, Mendez MD. Food allergies [Updated July 24, 2023]. In: StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing; 2025.
2. Nowak-Węgrzyn A, Chehade M, Groetch ME, et al. International consensus guidelines for the diagnosis and management of food protein-induced enterocolitis syndrome: executive summary—workgroup report of the Adverse Reactions to Foods Committee, American Academy of Allergy, Asthma & Immunology. J Allergy Clin Immunol. 2017;139(4):1111-1126.
3. Parzanese I, Qehajaj D, Patrinicola F, et al. Celiac disease: from pathophysiology to treatment. World J Gastrointest Pathophysiol. 2017;8(2):27-38.
4. Gargano D, Appanna R, Santonicola A, et al. Food allergy and intolerance: a narrative review on nutritional concerns. Nutrients. 2021;13(5):1638.
5. Mousavi Khaneghah A, Mostashari P. Decoding food reactions: a detailed exploration of food allergies vs. intolerances and sensitivities. Crit Rev Food Sci Nutr. 2025;65(14):2669-2713.
6. Skodje GI, Sarna VK, Minelle IH, et al. Fructan, rather than gluten, induces symptoms in patients with self-reported non-celiac gluten sensitivity. Gastroenterology. 2018;154(3):529-539.
7. Mennini M, Ferrari F, Parisi P, Di Nardo G. Gluten and non-coeliac gluten sensitivity: the nocebo effect and future avenues. Lancet Gastroenterol Hepatol. 2024;9(4):292-293.
8. Caminero A, Meisel M, Jabri B, Verdu EF. Mechanisms by which gut microorganisms influence food sensitivities. Nat Rev Gastroenterol Hepatol. 2019;16(1):7-18.
9. Caminero A, McCarville JL, Galipeau HJ, et al. Duodenal bacterial proteolytic activity determines sensitivity to dietary antigen through protease-activated receptor-2. Nat Commun. 2019;10(1):1198.
10. Cárdenas-Torres FI, Cabrera-Chávez F, Figueroa-Salcido OG, Ontiveros N. Non-celiac gluten sensitivity: an update. Medicina (Kaunas). 2021;57(6):526.
11. Sharma P, Brown S, Sokoya EM. Re-evaluation of dietary interventions in rheumatoid arthritis: can we improve patient conversations around food choices?. Rheumatol Int. 2024;44(8):1409-1419.
12. Geiselman JF. The clinical use of IgG food sensitivity testing with migraine headache patients: a literature review. Curr Pain Headache Rep. 2019;23(11):79.
13. Durham SR, Shamji MH. Allergen immunotherapy: past, present and future. Nat Rev Immunol. 2023;23(5):317-328.
14. de Graaf MCG, Lawton CL, Croden F, et al. The effect of expectancy versus actual gluten intake on gastrointestinal and extra-intestinal symptoms in non-coeliac gluten sensitivity: a randomised, double-blind, placebo-controlled, international, multicentre study. Lancet Gastroenterol Hepatol. 2024;9(2):110-123.
15. Zingone F, Bertin L, Maniero D, et al. Myths and facts about food intolerance: a narrative review. Nutrients. 2023;15(23):4969.
16. Malone JC, Daley SF. Elimination diets. In: StatPearls. Treasure Island, FL: StatPearls Publishing; 2024.
17. Mattes JA. The Feingold diet: a current reappraisal. J Learn Disabil. 1983;16(6):319-323.
18. Lange KW, Reissmann A, Nakamura Y, Lange KM. Food intolerance and oligoantigenic diet in children with attention-deficit hyperactivity disorder. Food Sci Hum Wellness. 2024;13(4):1729-1738.
19. Ostrowska L, Wasiluk D, Lieners CFJ, Gałęcka M, Bartnicka A, Tveiten D. IgG food antibody guided elimination-rotation diet was more effective than FODMAP diet and control diet in the treatment of women with mixed IBS-results from an open label study. J Clin Med. 2021;10(19):4317.
20. Namazova-Baranova L, Efendieva K, Levina J, Kalugina V. Food allergy and food intolerance—new developments. Global Pediatrics. 2024;9:100201.