Food Allergy vs. Food Sensitivity: What Testing Shows

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Two people say "I'm allergic to that" and mean completely different things. One means their throat closes. The other means they feel heavy and bloated for the rest of the afternoon. Both are describing something real, and confusing the two is how people end up either taking a genuine risk lightly or giving up food they never needed to give up.

The distinction is not pedantry. It decides which test is worth running, what the result means, and whether the answer is an emergency plan or a two-week experiment with your lunches.

True Food Allergy

A true food allergy is an immune reaction driven by IgE antibodies. A tiny amount of the protein triggers a response within minutes to a couple of hours, and it is the same reaction each time. Hives, swelling of the lips, tongue or throat, wheezing, vomiting and a sudden drop in blood pressure sit at this end of the spectrum.

In the United States nine foods account for most serious reactions: milk, eggs, peanuts, tree nuts, wheat, soy, fish, crustacean shellfish, and sesame, which became the ninth major allergen under the FASTER Act and has had to be labelled since January 2023.

Diagnosis belongs with a physician or allergist and rests on skin prick testing, specific IgE bloodwork, and where necessary a supervised oral food challenge, which is still the reference standard. Testing alone is not enough. A positive IgE result in someone who eats the food happily is a sensitisation, not an allergy, which is exactly why the number has to be read against the history rather than on its own.

Food Intolerance

Intolerance does not involve the immune system at all. Lactose intolerance is the clean example: the enzyme that breaks lactose down is in short supply, the sugar reaches the colon undigested, bacteria ferment it, and the result is gas, cramping and loose stools. Unpleasant, dose-dependent, not dangerous. Most people with it manage a splash of milk in coffee and get into trouble with a bowl of ice cream, which is a pattern you almost never see with a true allergy.

Histamine intolerance, sulphite sensitivity and reactions to fermentable carbohydrates, the FODMAP group, behave the same way. Threshold effects rather than all-or-nothing ones.

Food Sensitivity, and Why the Testing Is Contested

The middle ground is where nearly all the confusion and nearly all the commerce sits. People report delayed, dose-related symptoms after certain foods: bloating that builds over hours, headache, congestion, joint aches, skin flares, low mood, fatigue. These reports are consistent enough and common enough that waving them away is not good medicine either.

The disagreement is about how to find the culprits. IgG food antibody panels are widely sold for this, and their status is worth stating plainly: the major allergy bodies, including the American Academy of Allergy, Asthma and Immunology, advise against using IgG testing to diagnose food allergy. The reasoning is sound. IgG4 antibodies to food look like a normal marker of exposure and developing tolerance, so a "positive" frequently means little more than that you eat that food often.

That is a real limitation and it is not the whole story. What the evidence does support is using a panel to personalise an elimination trial rather than to diagnose anything. A randomised, sham-controlled trial published in Gut in 2004 found that people with irritable bowel syndrome who removed foods flagged by testing improved more than those removing the same number of foods chosen at random, and a larger multicentre randomised trial in Gastroenterology in 2025 reached the same conclusion for abdominal pain.

So the defensible position is narrow but genuinely useful: a panel is a way of deciding which foods to try removing first. It is not a diagnosis, it does not detect allergy, and a report listing thirty reactive foods should make you more sceptical rather than less. We use food sensitivity testing that way, and we say so before you pay for it.

The Test That Costs Nothing

A structured elimination and reintroduction is still the most informative thing available for suspected sensitivity, and it is free. Remove the suspected food completely for two to three weeks, keep written notes rather than impressions, then reintroduce it deliberately on its own and watch the following seventy-two hours.

Two rules separate an experiment from a guess. Change one thing at a time, because dropping six foods at once tells you nothing about which one mattered. And reintroduce properly, because the reintroduction is the actual test; the removal phase is only preparation. People skip that step constantly and end up avoiding food for years on the strength of a fortnight they half remember.

Where Food Reactions Fit With Everything Else

Food reactions rarely arrive alone. A list of foods that "don't agree with me" that keeps getting longer is more often a sign that something upstream is wrong than that you have developed thirty new sensitivities. Bacterial overgrowth, low enzyme output, gut inflammation and yeast overgrowth all produce exactly that pattern, which is why digestive and stool testing often runs alongside a food panel rather than after it.

It is also why we test before recommending a detoxification program rather than after. If one or two foods are provoking you, removing them is the intervention, and no cleanse will outperform it. Our post on testing before a detox sets out that order of operations in full.

One Number Worth Carrying Around

Research led by Ruchi Gupta and published in JAMA Network Open in 2019 found that while roughly 19 percent of US adults believed they had a food allergy, about 10.8 percent had symptoms consistent with a genuine one. Close to half the people who think they are allergic are describing something else.

That cuts both ways, which is why it is worth knowing. A great many people are avoiding food for no reason. And the ones who genuinely are allergic are surrounded by people using the word loosely, which is precisely how a restaurant kitchen learns to take it less seriously than it should.

What We Do Here

The history comes first, because the pattern usually narrows things before any sample is drawn. Timing, dose dependence, whether it happens every single time, and what else was going on that week all point somewhere. Where a panel would genuinely help shape an elimination trial, we run one and read it as a shortlist. Where the answer is that you need an allergist, we say so and help you get there.

Food sensitivity testing does not diagnose disease, and none of this replaces medical care. Suspected true food allergy belongs with a physician, as does unexplained weight loss, blood in the stool, difficulty swallowing or a persistent change in bowel habit.

Our functional medicine testing page covers the panels in detail and digestive health covers the wider picture. To talk it through, call (770) 674-6311 or request an appointment . We see patients from Roswell, Alpharetta, Johns Creek, Atlanta and across the north metro.

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Food Allergy vs. Food Sensitivity: What Testing Actually Shows

True Food Allergy

Food Intolerance

Food Sensitivity, and Why the Testing Is Contested

The Test That Costs Nothing

Where Food Reactions Fit With Everything Else

One Number Worth Carrying Around

What We Do Here

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