Food Allergies, Intolerances, and Sensitivities: The Ultimate Guide to Understanding Your Body’s Reactions
Key Takeaways
Learn the differences between food allergies (IgE), food intolerances (enzymes), food sensitivities (non-IgE immune pathways), celiac disease and several other food reactions—and why it matters for our long-term health.
Discover how the gut and immune system work together to process everything we eat—including where reactions can occur.
See how even "healthy" foods like carrots, salmon, or turmeric can cause inflammatory reactions in certain individuals, explaining why standard "anti-inflammatory" diets often fail.
Personalized Path Forward: Learn how Optimal AF can help you pinpoint unique sensitivities, reduce inflammation, and reclaim your vitality.
Why Food Reactions Matter
Food is medicine... and certain foods can also be problematic for some people.
You may know someone who carries an EpiPen for a peanut allergy, turns bright red after drinking alcohol, or experiences unexplained symptoms they suspect are food-related but can't be certain.
Everything we eat prompts a response in our body. Often this response is beneficial or even neutral—but for some people or in certain contexts, those responses spark inflammation or other adverse effects. Even whole, organic, "clean" foods instigate responses ranging from beneficial to irritating or even life-threatening—depending on our individual biochemistry.
Food allergies, sensitivities, intolerances, and celiac disease are often misunderstood or mistakenly lumped together. Understanding their distinct mechanisms is crucial for finding relief from chronic symptoms.
How We Process and Respond to Food
Before we delve into the different food reactions, it helps to understand two interconnected systems:
Our Digestive System extracts nutrients from what we eat to create fuel; and
Our Immune System evaluates those nutrients for compatibility with your unique biochemistry
Our Digestive System: The Incredible Food Processing System
Our digestive system is essentially a sophisticated fuel-processing factory. It transforms everything we eat into essential nutrients that power our bodies.
To understand our digestive system consider what happens to a strawberry when we eat it:
Before our first bite, aromatic molecules enter our nose, alerting our brain to what's coming. As we bite, our teeth crush the strawberry while saliva enzymes begin breaking down its sugars.
This forms a soft bolus that travels to our stomach, where acid and pepsin further dismantle its proteins into a nutrient-rich mixture called chyme.
From the stomach, chyme moves into our small intestine. Here, our pancreas and liver provide additional specialized enzymes and bile that transform the strawberry into its simplest components: sugars, amino acids, and fatty acids.
Millions of tiny villi that line our small intestine absorb these nutrients directly into our bloodstream, where they:
Provide energy (sugars)
Repair and build tissue (amino acids)
Maintain healthy cells (fatty acids)
As the remaining, mostly fiber-rich material moves into our large intestine (colon), water and electrolytes are absorbed. Here, our gut microbiome continues to break down fibers, generating beneficial compounds and gases along the way.
Eventually, what's left accumulates in our rectum as stool. When enough stool accumulates, stretch receptors in our rectum signal our brain that it's time for elimination. When ready, coordinated muscle contractions push the waste out, completing the remarkable digestive journey that began the moment we bit into that juicy strawberry.
Our Immune System: A Master of Homeostasis
The dominant metaphor used by Western science and medicine frames our immune system in terms of war and defense. Our body is portrayed as a battlefield, with the immune system responsible for identifying and destroying "invaders" such as bacteria, viruses, and other foreign pathogens. White blood cells and anti-bodies are frequently described as "soldiers" and pathogens as "enemies."
This perspective misses a fundamental truth: humans evolved as part of the natural world, not separate from it. Our bodies, like all of Nature, are constantly seeking homeostasis, a state of dynamic equilibrium where all systems function optimally together.
Homeostasis is is not a static condition, but rather a continuous process of adaptation and adjustment to keep our internal environment stable despite external changes. Recent research highlights how a bidirectional communication between our gut and our brain plays a critical, even dominant, role in maintaining this balance throughout our body [1].
Approximately 70% of our immune system resides in our gut, housed within specialized cells known as gut-associated lymphoid tissue (GALT) [2]. The remainder of our immune system is distributed throughout our body in cells that maintain constant communication both internally and with the external environment. When we eat, this network samples and evaluates each component through specialized cells lining our digestive tract.
How Our Immune System Evaluates Food: A Three-Part Process
Immune Cells: The Assessment Team
When we eat something, specialized immune cells form the frontline of our food evaluation system, sampling everything to determine if it should continue to the next stage or if a reaction is warranted;
Dendritic cells lining our digestive tract continuously sample food proteins, acting as information gatherers
T cells receive this information and help determine whether to develop tolerance or reaction
Mast cells and basophils can release histamine and other compounds during allergic reactions
Eosinophils may become involved in delayed allergic responses
These cells work cooperatively to maintain balance, with some focused on tolerance and others ready to respond if needed.
Antibodies: The Recognition System
Within our immune cells are antibodies. Antibodies are specialized proteins that our immune system uses to identify, interact with, and remember external substances. There are five known types of antibodies (IgE, IgG, IgM, IgA, and IgD), with four playing significant roles in food reactions:
Immunoglobulin E (IgE): This antibody drives true allergic reactions. IgE antibodies quickly recognize allergens, causing mast cells and basophils to release histamine and other mediators, leading to immediate symptoms. We might think of IgE antibodies like the emergency alert notification system on our cell phone—if we come into contact with an allergen, it's designed to get immediate attention, by sending out loud signals to get our immediate attention.
Immunoglobulin G (IgG): These antibodies, the most abundant in our bloodstream, primarily record exposure to foods and other substances. While some sensitivity tests measure IgG, these antibodies often simply indicate that we've encountered these foods before, not necessarily that they're problematic [3]. We might think of these as our body's memory system—like photos in our phone's gallery that remind us of places we've visited.
Immunoglobulin M (IgM): These are our body's first-contact team. When we try a new food, IgM antibodies are the first to respond and evaluate it, similar to how we have an initial impression when meeting someone new. They appear early in the immune response and typically handle the first exposure to new substances.
Immunoglobulin A (IgA): Primarily found in mucosal surfaces, IgA plays a crucial role in maintaining the integrity of the gut barrier and neutralizing potentially harmful substances.
(Note: Immunoglobulin D (IgD) is the fifth antibody type but plays a less understood role in food reactions specifically.)
Mediators: The Communication Network
When immune cells and antibodies sense a potential issue with food, they release immune mediators—signaling molecules that orchestrate the body’s next moves. Think of these mediators like dispatchers sending out instructions to different parts of your immune system that some sort of response is needed. Over a hundred types of mediators circulate in our body, and they can either spark or soothe inflammation.
Some key mediators include:
Cytokines: messaging proteins that rally other immune cells
Prostaglandins: triggers that help drive inflammation
Leukotrienes: signals that sustain the inflammatory response
Complement proteins: a system that boosts immune efficiency
We’ll look more closely at these mediators when we explore food sensitivities. Under normal conditions, they help maintain a delicate balance between tolerance and reaction. Sometimes, however, the immune system misfires—reacting unnecessarily to harmless foods. That’s where the range of food-related immune reactions begins.
Food Reactions Explained
Types of Food Reactions Explained:
Food Allergy
Food Intolerance
Food Sensitivity
Celiac Disease
Non-Celiac Gluten Sensitivity (NCGS)
Food Allergies: When IgE Takes Center Stage
What is a Food Allergy?
Food allergies are the most dramatic and potentially life-threatening of all food reactions. Allergies are immune system responses that occur when the body identifies certain proteins in food as harmful.
Understanding Food Allergies
When someone with a food allergy is exposed to their allergen initially, their immune system creates IgE antibodies.
When the person is re-exposed to the allergen, the IgE antibodies trigger a massive release of the immune mediator histamine that cause the classic symptoms of an allergic reaction.
Histamine has widespread effects on the body, ranging from mild to life threatening.
Here’s a breakdown of histamine’s key effects on different systems in the body:
Respiratory System Effects: Causes smooth muscle contraction in airways (leading to difficulty breathing, wheezing, shortness of breath), increases mucus production (causing nasal congestion and runny nose), and can trigger or worsen asthma attacks in susceptible individuals
Cardiovascular System Effects: Causes blood vessels to dilate (leading to flushing and low blood pressure), increases vascular permeability (resulting in swelling/edema and hives/urticaria)
Neurological Effects: Stimulates nerve endings (causing itching and tingling, especially in the skin) and can trigger headaches or migraines through vasodilation in the brain
Gastrointestinal Effects: Causes smooth muscle contraction in the GI tract (leading to cramps, nausea, vomiting, and diarrhea)
Immunological Role: Acts as a pro-inflammatory mediator that recruits other immune cells like eosinophils and basophils, amplifying the allergic response
In severe cases, these histamine-induced changes can lead to anaphylactic shock, a life-threatening medical emergency that requires immediate treatment.
➨ All of these responses are meant to move the offending substance(s) through the system as quickly as possible in an effort to restore balance.
The key characteristics of true food allergies are:
They involve IgE antibodies
Reactions occur quickly (usually within minutes to 2 hours)
Even tiny amounts of the allergen can trigger massive symptoms
Reactions happen consistently with each exposure
Some people experience milder allergic reactions that they might not recognize as allergies. For instance, someone might experience an itchy mouth or throat when eating certain raw fruits or vegetables (known as oral allergy syndrome) and simply consider it normal rather than identifying it as an allergic response.
Common Food Allergies
True food allergies affect an estimated 2–5% of adults and 4–8% of children in the United States, though some studies suggest the prevalence may be even higher [4]. As of 2023, nine foods—often called the “Big Nine”—are recognized as causing around 90% of serious allergic reactions:
Milk
Eggs
Fish
Shellfish
Tree nuts
Peanuts
Wheat
Soybeans
Sesame (officially added in 2023 by the FASTER Act)
How Are Food Allergies Diagnosed?
The gold standard for diagnosing food allergies is the skin prick test. A tiny drop of the suspected allergen goes on the skin, followed by a light prick so it can enter just beneath the surface. If you have IgE antibodies to that allergen, you’ll usually develop a raised, red bump (a wheal), confirming an allergic response.
Food allergy testing is generally covered by medical insurance, and most people with true food allergies know they have them due to the immediate and consistent nature of their reactions.
Food Intolerances: It’s (Usually) About Enzymes
What is a Food Intolerance?
The next type of common reaction is food intolerance. You may know someone who experiences digestive distress after eating cheese or who turns bright red when they drink alcohol. These are likely food intolerances.
Understanding Food Intolerances
Food intolerances account for roughly 15–20% of adverse food reactions—whereas true allergies (IgE-driven) make up only 2–5% [5].
Unlike allergies, which involve the immune system, food intolerances generally stem from the body’s inability to fully digest or handle certain components of food. This is often due to an enzyme deficiency, a chemical sensitivity, or other non-immunologic factors.
To understand food intolerances, think of our digestive system as a series of specialized demolition crews, each equipped with specific tools (enzymes) designed to break down different components of food so it can be processed by the next crew. When we eat something, these crews work in sequence to dismantle the food into usable nutrients.
In lactose intolerance, for example, the crew responsible for breaking down milk sugar is missing its key tool—the lactase enzyme. Without this specialized tool, the lactose remains intact as it moves through the digestive tract. When unprocessed milk sugars reach the colon, the bacteria there feast on them, producing excess gas, water, and short-chain fatty acids that cause the uncomfortable symptoms of bloating, gas, and diarrhea.
An important distinction is that these digestive enzymes operate outside the immune system. They're simply specialized proteins that help break down food components—not immune factors that identify and respond to potentially harmful substances. This is why, unlike allergies, taking supplemental enzymes (like Lactaid for lactose intolerance) can often help manage intolerances by providing the missing digestive tools.
Food intolerances typically develop due to:
Enzyme deficiencies: For example, lactose intolerance occurs when we lack sufficient lactase enzyme to break down lactose (milk sugar).
Chemical sensitivities: Reactions to naturally occurring chemicals in foods, such as caffeine or histamine.
Pharmacological factors: Reactions to biologically active compounds that affect bodily systems, such as tyramine in aged foods that can affect blood vessels and blood pressure.
Additives and preservatives: Reactions to sulfites, MSG, or certain food colorings.
Common Food Intolerances
Lactose Intolerance: Affects approximately 65% of the global population [6], with higher rates in East Asian populations (over 90%). People with lactose intolerance can often take lactase enzyme supplements before consuming dairy to prevent symptoms.
Alcohol Intolerance: Particularly common in East Asian populations due to genetic variants affecting alcohol metabolism enzymes. Some people lack sufficient alcohol dehydrogenase or aldehyde dehydrogenase enzymes, causing alcohol or its byproducts to build up in the body.
Histamine Intolerance: Occurs when our bodies cannot properly break down histamine in foods like aged cheese, fermented foods, or certain alcoholic beverages due to insufficient diamine oxidase (DAO) enzyme. This is different from the histamine our bodies produce during allergic reactions—this intolerance involves histamine naturally present in certain foods.
FODMAP Intolerance: Sensitivity to fermentable oligosaccharides, disaccharides, monosaccharides, and polyols found in various foods. These short-chain carbohydrates are poorly absorbed in our small intestine and can cause digestive distress when they reach our large intestine [5].
Symptoms of Food Intolerances
Food intolerances primarily affect our digestive system, causing symptoms such as:
Bloating and gas
Abdominal pain
Diarrhea
Nausea
Headaches (in some cases)
Flushing or skin redness (particularly with alcohol intolerance)
Unlike allergies, intolerances are often dose-dependent, meaning we might tolerate small amounts of the problematic food without symptoms, but experience issues when consuming larger quantities.
How Are Food Intolerances Identified?
Identifying food intolerances typically involves:
Elimination diets: Removing suspected trigger foods from our diet, then reintroducing them one by one to identify reactions
Breath tests: For certain intolerances like lactose or fructose, measuring hydrogen or methane in our breath after consuming the substance
Enzyme activity tests: In some cases, testing for the presence or activity of specific enzymes
Many people with food intolerances can manage symptoms by either avoiding trigger foods, consuming them in limited quantities, or taking appropriate enzyme supplements to aid digestion.
Food Sensitivities: An Overlooked Driver of Chronic Inflammation
What are Food Sensitivities?
Food sensitivities are immune-related—but non-IgE-mediated—reactions to certain foods that trigger a low-grade, and often chronic, inflammatory response in the body.
This category represents the most complex, subtle, and often misunderstood type of food reaction.
Like food allergies, every individual may have food sensitivities unique to their personal biochemistry.
Unlike food allergies, sensitivity reactions often develop hours—or even days—after eating a particular food, making them challenging to detect through simple observation.
Understanding Food Sensitivities
When we consume a food we're sensitive to, our white blood cells (neutrophils, monocytes, eosinophils, and lymphocytes) respond to components of that food by releasing inflammatory mediators.
When these mediators are released, they often trigger a wide range of symptoms throughout the body:
Cytokines: These signaling proteins can cause fatigue, body aches, and cognitive changes when released in response to food sensitivities.
Prostaglandins: Can lead to pain, inflammation, and sometimes fever.
Leukotrienes: Often involved in respiratory symptoms and inflammatory skin conditions.
Histamine: Even in non-IgE reactions, histamine release can cause symptoms like headaches, skin flushing, and digestive discomfort.
Platelet activating factor: A potent mediator that affects blood vessels and can contribute to migraines and other vascular symptoms.
Think of food sensitivities like a slow-building traffic jam. While a food allergy is like an immediate car crash that blocks all lanes (causing immediate, obvious symptoms), a food sensitivity is more like a gradual buildup of congestion across multiple roads in your body. The initial trigger might not cause immediate problems, but over days, months or even years, the "traffic" of inflammatory mediators builds up and affects multiple "neighborhoods" in our body—from our joints to our skin to our brain.
Clinical Complexities of Food Sensitivities
Food and food-chemical sensitivities have several clinical characteristics that make identifying trigger foods exceptionally challenging:
Delayed reactions: Symptoms may be delayed by up to 96 hours after ingestion, or may go completely unrecognized as a food-related symptom at all.
Dose-dependency: Acute reactions may only occur when a certain threshold amount is consumed.
Counterintuitive triggers: Even so-called anti-inflammatory foods, such as salmon, parsley, turmeric, ginger, and blueberry—any "healthy" food—can be reactive for certain individuals.
Testing is challenging: There are an estimated 10,000 different food ingredients and food chemicals in a typical American grocery store. No test can assess that many foods.
Despite their significant role as a source of inflammation in conditions like IBS, migraine, fibromyalgia, arthritis, GERD, obesity, metabolic syndrome, ADD/ADHD, and autism, food and food-chemical sensitivities remain one of the most under-addressed areas of conventional medicine.
Food Sensitivities Case Study
One of our clients at Optimal AF had already cut out common triggers like wheat, dairy, alcohol, and grains to address persistent stomach issues. However, she still experienced daily digestive distress.
Advanced sensitivity testing revealed an unexpected culprit: carrots. Once she removed carrots from her diet, her GI issues finally resolved. This underscores how unique and unpredictable food sensitivities can be—sometimes it's not the usual suspects!
Symptoms of Food Sensitivities
Food sensitivities can manifest in numerous ways, affecting multiple body systems:
How Are Food Sensitivities Diagnosed?
Diagnosing food sensitivities can be challenging due to their delayed nature and wide-ranging symptoms. Current approaches include:
Elimination Diets: The gold standard involves removing suspected trigger foods for a period of time, then systematically reintroducing them while monitoring symptoms. While effective, traditional elimination diets can be extremely restrictive and time-consuming. You can read our in-depth blog about Elimination Diets --> [Here]
IgG Food Antibody Tests: While popular, these tests have significant limitations. The presence of IgG antibodies to foods often simply indicates exposure, not necessarily sensitivity. Many leading allergist organizations have cautioned against using IgG testing alone for diagnosing food sensitivities [3].
Mediator Release Testing (MRT): This advanced approach measures changes in the liquid-to-solid ratio of your blood after exposure to various foods and chemicals, directly measuring the end result of all potential hypersensitivity reactions. By measuring mediator release rather than a single pathway, this test captures the final common pathway of all food sensitivity reactions [7].
Cell-Based Assays: Some newer tests measure the response of immune cells when exposed to food extracts. The MRT is an example of a cell-based assay.
At Optimal AF, we’ve developed a comprehensive, personalized approach—combining advanced testing, with the Gold Standard of elimination protocols, and ongoing guidance—to help you address your unique triggers and move forward with confidence.
We offer the MRT Test as part of all our packages: https://optimalaf.com/start
Celiac Disease & Non-Celiac Gluten Sensitivity (NCGS)
What is Celiac Disease?
Celiac disease is an autoimmune disorder triggered by consuming gluten, a protein found in wheat, barley, and rye.
Understanding Celiac Disease
When someone with celiac eats even a small amount of gluten (say a bite a of regular bread), the gluten triggers an autoimmune response where their immune system mistakenly attacks the lining of their small intestine.
Specifically, their immune system targets the villi—those small, finger-like projections that line the small intestine and are responsible for nutrient absorption. As these villi become damaged and flattened (a condition called villous atrophy), the body's ability to absorb nutrients becomes severely compromised.
Over time, this damage leads to nutrient deficiencies, despite eating a seemingly nutritious diet. It's like having a sponge with most of its absorptive surface worn away—it simply can't soak up nutrients properly anymore.
Celiac disease has a strong genetic component, with first-degree relatives of people with celiac disease having a 20% risk of developing the condition themselves. It affects approximately 1% of the population worldwide [8].
Symptoms of Celiac Disease
Celiac disease can manifest with a wide range of symptoms that vary greatly from person to person:
Digestive Symptoms
Diarrhea
Bloating and gas
Abdominal pain
Nausea and vomiting
Weight loss
Non-Digestive Symptoms
Fatigue
Anemia
Bone or joint pain
Arthritis
Osteoporosis
Skin rash (dermatitis herpetiformis)
Headaches or migraines
Neurological symptoms (tingling, numbness, or pain in hands and feet)
Depression or anxiety
Missed menstrual periods
Infertility or recurrent miscarriage
Interestingly, some people with celiac disease (particularly adults) have few or no digestive symptoms, making diagnosis challenging. These "silent" or "atypical" presentations of celiac disease can still cause significant internal damage and long-term health consequences, even without obvious symptoms.
How is Celiac Disease Diagnosed?
Identifying celiac disease typically involves a multi-step process:
Blood Tests: Screening for certain antibodies, such as tissue transglutaminase antibodies (tTG-IgA) and endomysial antibodies (EMA-IgA)
Genetic Testing: Looking for HLA-DQ2 and HLA-DQ8 genes associated with celiac disease
Intestinal Biopsy: The definitive diagnostic procedure involves taking a small tissue sample from the small intestine during an endoscopy to check for damage to the villi
Response to Gluten-Free Diet: If symptoms improve on a strict gluten-free diet, this supports the diagnosis
For people with celiac disease, the only effective treatment is a strict gluten-free diet. Even tiny amounts of gluten can trigger the autoimmune response and cause damage to the intestine. This means avoiding not just obvious sources like bread and pasta, but also being vigilant about cross-contamination and hidden sources of gluten in processed foods, medications, and even some supplements.
Non-Celiac Gluten Sensitivity
What is Non-Celiac Gluten Sensitivity?
Non-Celiac Gluten Sensitivity (NCGS) is a condition where individuals experience symptoms similar to celiac disease when consuming gluten, but without the intestinal damage or positive test results characteristic of celiac disease.
Understanding Non-Celiac Gluten Sensitivity
When someone with NCGS eats foods containing gluten, they may experience a range of uncomfortable symptoms. However, unlike celiac disease, these symptoms aren't caused by an autoimmune attack on the intestinal villi. Instead, NCGS appears to involve different immune pathways and potentially other mechanisms that aren't yet fully understood.
Think of it this way: If celiac disease is like an autoimmune attack that damages our home's foundation (the intestinal villi), NCGS is more like an alarm system that goes off when gluten enters, creating discomfort without causing structural damage to the house.
The exact mechanisms behind NCGS are still being researched, but it appears to involve activation of innate immune pathways rather than the adaptive immune response seen in celiac disease. Studies suggest that people with NCGS may have increased intestinal permeability and systemic immune activation in response to gluten, despite not having the characteristic antibodies or intestinal damage of celiac disease.
Non-celiac gluten sensitivity (NCGS) affects approximately 6% of the population, though prevalence estimates vary widely in different studies from 0.5% to 13% depending on the diagnostic criteria used and the population studied [9]. This makes it more common than celiac disease, which affects about 1% of the population worldwide.
Symptoms of NCGS
Symptoms often overlap with those of celiac disease and can include:
Digestive issues (bloating, abdominal pain, diarrhea, constipation)
Fatigue
Headaches
"Brain fog" and difficulty concentrating
Joint and muscle pain
Skin rashes
Anxiety and depression
Numbness in extremities
These symptoms typically appear within hours to days after consuming gluten and improve when gluten is removed from the diet.
How is NCGS Identified?
Since there are no specific biomarkers for NCGS, identification is made through a process of elimination:
Exclusion of Celiac Disease and Wheat Allergy: First ruling out these conditions through appropriate testing
Gluten Challenge: Removing gluten from the diet to see if symptoms improve, then reintroducing it to see if symptoms return
Controlled Gluten Challenge: In some clinical settings, a double-blind, placebo-controlled gluten challenge may be used to confirm the diagnosis
For people with NCGS, a gluten-free diet is the primary management strategy, although the level of gluten restriction needed may be less strict than for those with celiac disease. Some individuals with NCGS find they can tolerate small amounts of gluten occasionally, while others need to avoid it completely to remain symptom-free.
Other Gluten-Related Disorders
Beyond celiac disease and NCGS, there are other ways gluten can affect our health:
Wheat Allergy: A true IgE-mediated allergic reaction to proteins in wheat (which may include gluten)
Gluten Ataxia: A neurological condition characterized by damage to the cerebellum due to gluten exposure
Dermatitis Herpetiformis: An intensely itchy skin condition linked to gluten sensitivity
Other Factors to Consider
In addition to gluten-related disorders, numerous other dietary and environmental elements can affect digestive health and immune balance. Some of these do not necessarily trigger an immune response in the same way a food allergy might; rather, they may involve metabolic pathways, the microbiome, or enzyme function. Here are a few examples:
Pesticides and the Gut Microbiome
Modern agricultural practices rely on chemical pesticides that has been shown to kill beneficial gut bacteria. For instance, certain herbicides have been shown to harm microbial diversity in the digestive tract [10], potentially contributing to dysbiosis (an imbalanced microbiome). This imbalance may not directly cause an immune-mediated reaction but can weaken the gut barrier, impact nutrient absorption, and disrupt normal immune signaling—setting the stage for a wide range of possible digestive and systemic issues.
Low FODMAP Diet
“FODMAP” is an acronym for Fermentable Oligo-, Di-, Mono-saccharides, and Polyols—carbohydrates that some people have difficulty digesting. Rather than triggering an immune response, these poorly absorbed sugars can be rapidly fermented by gut bacteria, leading to gas, bloating, and other symptoms (common in irritable bowel syndrome). The Low FODMAP Diet is not about eliminating an allergen or an enzyme deficiency per se; instead, it’s a short-term strategy used to pinpoint which specific FODMAP-containing foods aggravate a person’s gut and to guide better symptom management.
Purines
Purines are naturally occurring compounds found in many foods—particularly organ meats, certain seafoods, and some vegetables. They aren’t associated with food allergy or an enzymatic shortfall. Rather, high purine intake can increase uric acid levels in some individuals, heightening the risk of gout flare-ups and other metabolic issues. For those vulnerable to elevated uric acid, moderating purine-rich foods can be a practical approach to reducing flare risks.
Lectins
Lectins are proteins present in many plant foods (such as beans, grains, and some nightshades) that can bind to carbohydrates on cell surfaces. While lectins don’t necessarily trigger classic immune reactions, consuming large amounts of improperly cooked high-lectin foods may cause digestive irritation or discomfort in certain individuals. Proper cooking methods—like soaking, sprouting, or pressure-cooking—can significantly reduce the lectin content, making these foods more easily tolerated.
⸻
Each of these factors—pesticides, FODMAPs, purines, and lectins—may play a role in digestive discomfort or metabolic challenges, but they are not universally harmful or relevant to everyone. Personal susceptibilities vary widely. If you suspect any of these might be influencing your health, it’s wise to work with a healthcare professional to evaluate your diet and gut health more closely.
Why Do Food Reactions Develop?
The honest answer is that science still doesn’t fully understand why one person might develop a peanut allergy while another does not, or why one individual might be sensitive to salmon even though others tolerate it just fine. This is part of our unique biological blueprint—likely an interplay of genetics, environmental exposures, modern lifestyle factors, and the gut microbiome.
That said, researchers have identified several factors are known to contribute to the development of food reactions:
1. Intestinal Permeability ("Leaky Gut")
When the intestinal barrier becomes compromised because of inflammation, larger food particles can enter the bloodstream and potentially trigger immune responses. Causes of increased intestinal permeability include chronic stress, certain medications (like NSAIDs and antibiotics), infections, toxin exposure, and dysbiosis (an imbalanced gut microbiome).
Research confirms that heightened intestinal permeability can play a central role in the development of food sensitivities by granting partially digested proteins inappropriate access to immune cells [11].
2. Genetic Predisposition
Some people have genetic variants that make them more susceptible to food reactions, particularly those with:
Family history of autoimmune diseases
History of allergies
Certain HLA gene types
These genetic factors may amplify immune responses to specific food proteins, though not everyone with these variants will necessarily develop a food reaction.
3. Immune System Dysregulation
Any condition that disrupts normal immune function can increase the risk of developing food sensitivities. Examples include:
Chronic inflammation
Autoimmune conditions
Recurrent infections
Stress-related immune suppression
When the immune system is persistently “on alert,” it may overreact to harmless substances—including proteins in foods.
4. Dietary Patterns and Microbiome Diversity
Modern dietary habits likely also play a role. Diets dominated by processed foods or lacking in nutrient variety can reduce the diversity of gut microbes—and a healthy, diverse microbiome is essential for properly training the immune system.
Epidemiological data suggest that populations consuming traditional, less-processed diets tend to have lower rates of food sensitivities and autoimmune disorders. The shift toward industrialized eating patterns may partly explain rising rates of these conditions.
5. Modern Lifestyles and the Rise in Allergies
Autoimmune and inflammatory diseases have been on the rise in recent decades—and peanut allergies in particular appear more prevalent now than in earlier generations. Several factors related to modern lifestyles may contribute:
Reduced microbial exposure (“hygiene hypothesis”): Cleaner environments and lower exposure to diverse microbes in early life can lead to an overreactive immune system.
Increased pollution and chemical exposures: Environmental toxins may shift immune responses toward inflammation and allergy.
Changes in infant-feeding practices: Emerging research shows that early introduction of allergenic foods may reduce certain allergies, suggesting that delayed exposure could be contributing to a rise in food allergies [12].
Stressful, fast-paced living: Chronic stress can impair gut health and immune regulation, further increasing susceptibility.
While certain factors—like gut permeability, genetic predisposition, immune dysregulation, dietary habits, and modern lifestyles—are known to contribute to the rise in food reactions, no single explanation applies to everyone. Two people with similar risk profiles may still have vastly different outcomes. Ongoing research continues to unravel the precise mechanisms behind food allergies, intolerances, and sensitivities, but for now, it’s fair to say that we don’t yet have all the answers.
Conclusion: Your Path to Clarity
Understanding the differences between food allergies, intolerances, sensitivities, and conditions like celiac disease is crucial for identifying and addressing your unique food reactions. These reactions represent a complex but addressable cause of many chronic symptoms that might be impacting your quality of life.
Just as every human has a unique fingerprint, each of us has a microbiome and immune system as unique as that fingerprint. The journey to addressing food reactions requires patience and precision, but the rewards of increased energy, mental clarity, and overall well-being make it worthwhile.
Disclaimer: This article is for informational purposes only and is not intended as medical advice. Always consult with a qualified healthcare provider before making significant changes to your diet, especially if you have existing health conditions. Read our Full Blog Disclaimer Here
References
Cryan JF, O'Riordan KJ, Cowan CSM, et al. The Microbiota-Gut-Brain Axis. Physiol Rev. 2019;99(4):1877-2013. doi:10.1152/physrev.00018.2018
Vighi G, Marcucci F, Sensi L, Di Cara G, Frati F. Allergy and the gastrointestinal system. Clin Exp Immunol. 2008;153 Suppl 1(Suppl 1):3-6. doi:10.1111/j.1365-2249.2008.03713.x
Carr S, et al. CSACI Position statement on the testing of food-specific IgG. Allergy, Asthma & Clinical Immunology. 2012;8(1):12.
Sicherer SH, Sampson HA. Food allergy: a review and update on epidemiology, pathogenesis, diagnosis, prevention, and management. J Allergy Clin Immunol. 2018;141(1):41-58. doi:10.1016/j.jaci.2017.11.003
Zopf Y, Baenkler HW, Silbermann A, et al. The Differential Diagnosis of Food Intolerance. Dtsch Arztebl Int. 2012;109(48):809–818. doi: 10.3238/arztebl.2009.0359
Misselwitz B, et al. Lactose malabsorption and intolerance: pathogenesis, diagnosis and treatment. United European Gastroenterology Journal. 2019;7(8):1054–1065.
Pasula MJ. The Patented Mediator Release Test (MRT): A Comprehensive Blood Test for Inflammation Caused by Food and Food-Chemical Sensitivities. Townsend Letter. 2014
Kupfer SS, Jabri B. Pathophysiology of celiac disease. Gastrointest Endosc Clin N Am. 2012;22(4):639-660. doi:10.1016/j.giec.2012.07.003
Cárdenas-Torres FI, et al. Non-Celiac Gluten Sensitivity: An Update. Medicina. 2021;57(6):526. DOI: 10.3390/medicina57060526.
Claus SP, et al. The gut microbiota: a major player in the toxicity of environmental pollutants? NPJ Biofilms and Microbiomes. 2016;2:16003. DOI: 10.1038/npjbiofilms.2016.3.
König J, et al. Human Intestinal Barrier Function in Health and Disease. Clinical and Translational Gastroenterology. 2016;7(10). DOI: 10.1038/ctg.2016.54.
Du Toit G, et al. Randomized trial of peanut consumption in infants at risk for peanut allergy (LEAP). New England Journal of Medicine. 2015;372(9):803–813.
⸻
