Food Sensitivity Testing vs. Allergy vs. Intolerance: What It Really Means
- Jared C. Pistoia, ND
- 3 minutes ago
- 8 min read
If you're wondering what the difference is between a food sensitivity, food allergy, and food intolerance, then you're in the right place!
These three distinct concepts refer to different ways your body can react to food — but they're often confused or used interchangeably.
Understanding the difference is crucial if you're dealing with symptoms like bloating, fatigue, rashes, or digestive discomfort and trying to uncover the root cause.
In this article, we’ll break each one down in simple, clear terms — and explain how food sensitivity testing fits into the picture, when it makes sense to test, and how gut health plays a central role in all of it.
The Gut–Immune Connection: Where Most Health Issues Begin
Every time you eat, food passes through your digestive tract where it meets two critical systems: your gut lining and your immune system.
Your gut lining is made of specialized cells designed to absorb the nutrients your body needs while keeping out anything harmful — like toxins, microbes, or improperly digested food particles.
Your gut lining is a physical barrier between the outside of your body and the inside of your body. But this barrier isn’t just physical: it's also regulated by immune cells.
Lining your intestines are immune cells that act as gatekeepers. They continuously monitor what’s coming in, scanning for threats and tagging any suspicious compounds for removal or attack.
When this system works well, you can eat a wide variety of foods with no issue. But when things go wrong — when the gut becomes leaky or inflamed — the immune system begins to overreact, often to the very foods you eat every day.
What’s the Difference Between Food Sensitivity, Allergy, and Intolerance?
Not all food reactions are the same — but most people lump them together, assuming it's all the same thing. If you’ve ever been told you have a “food sensitivity,” you might be wondering: Is it an allergy? Is it dangerous? Do I have to stop eating that food?
Reaction to food in your gut is mediated by your immune system. This means that certain immune cells are involved in the decision about whether or not food is flagged as a problem.
If it's flagged, an immune reaction will take place and you'll experience symptoms. The way your immune system responds to a particular food is what determines whether it's an allergic response or sensitivity response.
Food Allergies
A food allergy is an immediate and exaggerated immune response. The body sees a certain food (like peanuts or shellfish) as a dangerous invader — even though it’s harmless to most people — and it launches a full-blown attack.
This reaction is usually triggered by IgE antibodies and can cause symptoms like hives, swelling, difficulty breathing, or even anaphylaxis.
Think of this as a fire alarm going off.
Food Sensitivities
Food sensitivities involve the immune system too, but in a slower, less obvious way. They’re often mediated by IgG antibodies, IgA antibodies, or complement activation, which means symptoms might not show up until hours or even days later. You might feel bloated, foggy, fatigued, or inflamed — without making the connection right away.
IgG is like an faulty home security system. It still works, but it's not very good at telling the difference between a real break-in and a squirrel on the porch. Every time you eat something your system doesn’t like, it may trip the alarm — even if the food isn’t truly harmful.
Food Intolerances
Food intolerance happens when your body lacks the proper enzymes to break something down. The classic example is lactose intolerance, where people don’t make enough lactase enzyme to digest dairy sugar.
This leads to bloating, gas, and discomfort — but it’s not an immune reaction and doesn’t cause inflammation in the same way.
What is IgA, IgG, IgE, and complement?
Generally, antibodies like IgG, IgA, and IgE are proteins made by your immune system. Their job is to identify things that don’t belong — like viruses, bacteria, or, in some cases, food particles — and signal your body to respond.
IgG – The Long-Term Tracker
Think of IgG as your body’s food memory. IgG antibodies are like long-term security cameras. They record your body’s past exposures to different foods or pathogens and may respond slowly if something seems “off.”
High IgG to a food doesn’t always mean danger — but it may suggest your immune system has flagged it for further surveillance.
IgA – The Bodyguard
IgA lives on the front lines of your mucous membranes — especially in your gut. These antibodies protect your inner surfaces, like your digestive tract, by binding to unwanted invaders and helping escort them out.
When IgA is elevated toward specific foods, it often means your gut lining is irritated — think leaky gut, infections, or digestive stress.
IgE – The Fire Alarm
IgE is the antibody involved in classic allergic reactions. This is the fast-acting, high-alert part of your immune system. It reacts immediately and forcefully to things it sees as dangerous — like peanuts, shellfish, bee stings, or pollen — and causes symptoms like hives, swelling, or even anaphylaxis.
Complement – The Amplifier
Complement proteins are like immune system grenades. They aren’t antibodies, but rather a group of proteins that “complement” your immune response.
When activated (especially alongside IgG), they create a more aggressive reaction — leading to tissue damage, inflammation, and chronic symptoms.
How Does Food Sensitivity Testing Work?
Most food sensitivity tests measure IgG antibodies. Food sensitivity tests collect a sample of your blood and then expose it to the foods in question. IgG levels are then measured and reported.
There are different types of IgG antibodies, each of which play a different role in the immune reaction. This is important to know because food sensitivity test kits vary in the type of IgG being tested.
Here are the basic IgG antibody types and what they do:
IgG 1 & IgG 3: These are the main “inflammatory” IgG types — when elevated against foods, they may indicate that exposures are triggering complement and other cell-messenger cascades which lead to symptoms.
IgG 2: Usually less relevant for foods.
IgG 4: Often rises with chronic exposure to food, indicating a type of tolerance to it. High levels of IgG 4 to foods may mean desensitization, not inflammation. This is why IgG4-based tests can be misleading if interpreted alone.
There are a few different types of food sensitivity test kits, usually measure one or more of the following:
Basic IgG 1–4 Panels: Measure exposure to food but don’t reveal if inflammation is occurring.
IgG + Complement Tests: Add a layer by testing C3d (complement activation), which helps identify foods that actually provoke inflammatory cascades.
IgA Panels: Reflect mucosal irritation (especially relevant in leaky gut or gut-lining inflammation).
In short, not all food sensitivity tests are created equal — the more comprehensive the panel, the clearer the picture of what’s truly happening in your gut.
What Do Food Sensitivity Results Actually Mean?
It depends on the type of food sensitivity test. Assuming it includes IgG 1 and 3, it means that there is probably an inflammatory response occurring after you eat those particular foods.
This type of reaction can occur when the particular food in question is triggering a systemic immune response, usually because it crossed the gut barrier prematurely.
If a food is resulting in a large production of IgA antibodies, then it's irritating your gut lining, but not necessarily causing a systemic reaction. You might consider giving that food a rest for a little while.
2025 research noted that IgG food reactivity can be a byproduct of a disrupted gut barrier. That’s why patients with leaky gut, dysbiosis, or chronic inflammation often show reactivity to multiple foods. Once the integrity of the barrier is restored, most of those reactivities fade over time.
What Does the Science Say About IgG Food Testing?
The evidence is mixed, controversial, and highly dependent on how the tests are interpreted. Critics argue that IgG presence only shows exposure and not a digestive issue. That’s partially true.
Research from 2015 shows that IgG4 combined with complement markers may provide more accurate insight into which foods are contributing to inflammation and resulting symptoms.
However, as previously stated, research cautions that IgG4 often reflects tolerance, not sensitivity, and that many clinicians still regard IgG4 tests with skepticism.
In my practice, I've found that food sensitivity tests — when used thoughtfully — can be helpful for:
Identifying patterns that correspond with patient symptoms
Motivating dietary changes and encouraging greater food diversity
Accelerating gut healing when paired with stool testing
When Is Food Sensitivity Testing Helpful?
This kind of testing isn’t for everyone and it's not always appropriate, even when you have digestive symptoms — but in the right context, it can fast-track healing.
Consider testing if you:
Have unexplained and chronic bloating, constipation, or IBS symptoms
Struggle with skin rashes, acne, or eczema
Experience joint pain or brain fog that flares after eating
Have already cleaned up your diet, but still aren’t seeing results
Often, these are signs of delayed immune reactions or gut barrier dysfunction — both of which can be supported by a food sensitivity panel.
How Is Food Sensitivity Related to Leaky Gut and the Microbiome?
Leaky gut (a.k.a. intestinal permeability) occurs when the tight junctions in your gut lining break down, allowing food particles and toxins to slip through and trigger immune responses.
Markers like zonulin (a protein that regulates permeability) and butyrate (a postbiotic that maintains gut barrier health) can show how well your gut is functioning. If you have low butyrate and high zonulin, there’s a good chance your food sensitivities are secondary to gut dysfunction.
That’s why food testing and stool testing often go hand in hand.
How Do I Choose the Right Food Sensitivity Test?
There are dozens of tests out there — I tend to use one of the following depending on what each patient needs. It's best to speak with a naturopathic doctor to determine which test makes the most sense for you.
Measures IgG1–4 + Complement
Identifies foods that trigger inflammatory cascades
Includes gut barrier markers
Great for patients with autoimmune or inflammatory symptoms
Can test up to 176 foods
Offers panels for IgG1-4 + IgA
IgA component is helpful for identifying mucosal reactivity
Can test up to 240 foods
Food explorer kit includes IgG1-4
Can be paired with IgE explorer kit
Can test up to 283 foods
KBMO's test is unique because it also includes the complement proteins, which really helps to hone in on problematic foods.
What Are the Limitations of Food Sensitivity Testing?
Food sensitivity testing can be helpful when you're making dietary changes that support gut health. However, there are several limitations:
It doesn’t identify the root cause — only downstream immune activity
False positives are common in leaky gut
Tests can lead to overly restrictive diets if not interpreted properly
Doesn’t address microbiome imbalances
What To Do After Food Sensitivity Testing
Even with results in hand, testing is just a first step. Here’s what I recommend next:
Visit a naturopathic doctor. Working with a professional is the best way to understand what to do with the information, and if additional testing makes sense.
Strategically eliminate and reintroduce. Labs typically recommend a change in your diet after getting the results. But don’t cut everything forever — reintroduce after 8–12 weeks of healing
Keep your gut as strong as possible. Maintaining a healthy gut barrier is essential to both immune function and overall gut health, as you now know. Start with my free Gut Health Daily Checklist to rebuild your foundation
Want More Natural Health Insights?
As a naturopathic physician, I believe that every person is unique—and so is their healing path. I take time to understand each patient’s story, physiology, emotional health, and lifestyle before making recommendations.
Whether I’m using nutrition, herbal medicine, homeopathy, or lifestyle
counseling, my goal is always the same: to identify and treat the true cause of illness so your body can restore balance on its own.
If you’re interested in a personalized, natural approach to health, I invite you to join my newsletter for more insights.
Subscribe to my blog to get regular updates on natural medicine, gut health, holistic healing, and the psychology of wellness.
Or reach out to schedule a consult—let’s uncover the real root cause of your symptoms and start your healing process.
