Allergy, sensitivity, intolerance, celiac — four different problems with food

“I think I’m allergic to something I eat” covers an enormous amount of ground. For one person it means lips that swell almost as soon as shrimp touches them. For another it means bloating and a headache that show up long after eating, and could be tied to any of several meals. For another it means diarrhea after ice cream, every time. For another it means fatigue, anemia, and loose stools that turn out to be celiac disease.

These are not four versions of the same thing. They involve different parts of the body, happen on different timelines, carry different levels of risk, and are tested in different ways. Getting the category right is the first step, because the wrong test or the wrong assumption can lead someone to restrict their diet unnecessarily — or to miss something that genuinely matters.

Food allergy: the immediate, IgE reaction

A true food allergy is an immune response driven by IgE antibodies. After an earlier exposure, the immune system has produced IgE specific to a food protein, and those antibodies sit on mast cells throughout the body. When the food is eaten again, the mast cells release histamine and other chemicals quickly. Reactions are typically immediate: hives, swelling of the lips, tongue, or throat, vomiting, wheezing, a drop in blood pressure. At the severe end this is anaphylaxis, which can be life-threatening.

Food allergy is diagnosed by an allergist, using skin prick testing, blood tests for food-specific IgE, and when needed a supervised oral food challenge. If you have ever had a reaction involving swelling, breathing difficulty, or collapse, or you carry an epinephrine auto-injector, that is a matter for your allergist, not for us. A food sensitivity panel does not test for this, and nothing in this article applies to managing it.

Food sensitivity: delayed, and far less straightforward

Food sensitivity usually refers to delayed, non-IgE immune reactions to food. The symptoms are slower to appear and less specific: bloating, altered bowels, headaches, joint aches, skin flares, fatigue, brain fog. Because the reaction is delayed, the link to a particular food is hard to see, especially when the food is eaten often.

Most food sensitivity panels measure IgG antibodies, sometimes including the IgG4 subclass, to a long list of foods. Here the honest picture matters. IgG to food is partly a normal sign of exposure — the immune system noticing something it encounters often — and major allergy organizations caution against using IgG results to diagnose food allergy or to justify broad elimination on their own. We agree with that caution. Where we find these panels useful is narrower: as a map of where the immune system is currently paying attention, to be tested against how a person actually responds to food.

Intolerance: no immune system involved

A food intolerance is a problem of digestion, not immunity. Lactose intolerance is the classic example: the small intestine makes too little lactase, the enzyme that splits milk sugar, so the lactose passes undigested to the colon, where bacteria ferment it into gas and draw in water. The result is bloating, cramping, and diarrhea after dairy, with no antibodies involved. Lactose intolerance is usually identified with a hydrogen breath test or a careful trial of removing and reintroducing dairy.

Other intolerances follow the same logic: poor absorption of fructose, sensitivity to fermentable carbohydrates when there is an overgrowth in the small intestine, or difficulty breaking down histamine from foods. An IgG panel will not detect any of these, because the immune system is not the problem.

Celiac disease: autoimmune, and in a category of its own

Celiac disease is an autoimmune condition. In genetically susceptible people, gluten triggers an immune attack on the lining of the small intestine, flattening the villi that absorb nutrients. It can cause digestive symptoms, but it can also appear as iron deficiency, low bone density, fatigue, rashes, or nothing obvious at all. It is not an allergy and not a sensitivity, and it requires strict lifelong gluten avoidance.

Celiac testing starts with blood work — tissue transglutaminase IgA along with total IgA, since low total IgA can produce a false negative — and is confirmed by biopsy. One practical point people often miss: you need to be eating gluten when tested. Going gluten-free first can make the tests look normal and leave the question unanswerable. If celiac is a possibility, test before you eliminate.

• Allergy. IgE-driven, immediate, potentially dangerous. Tested by an allergist.
• Sensitivity. Delayed, non-IgE, symptoms vague. IgG-type panels offer clues, not a diagnosis.
• Intolerance. Digestive, not immune. Tested with breath testing or structured trials.
• Celiac disease. Autoimmune reaction to gluten. Tested with specific antibodies and biopsy, while still eating gluten.

Using a sensitivity panel well

A food sensitivity panel can tell us which foods the immune system is currently producing antibodies to, and how strongly. It cannot tell us that a food is dangerous, that it will always cause symptoms, or that it needs to be avoided forever. It cannot rule out an allergy, celiac disease, or an intolerance.

So we treat results as the starting point for a structured process rather than a verdict. The highest-reacting foods are removed for a defined period. Then they are reintroduced one at a time, with space between each, while tracking symptoms. A food that brings the symptoms back is set aside for now. A food that comes back without trouble goes back into the diet, regardless of what the panel said. The body’s response is the final word, and the panel is how we decide where to look first.

A sensitivity result is not a lifelong list of forbidden foods. It is a question, and reintroduction is how we answer it.

Why sensitivities often follow a gut problem

When a panel comes back with reactions to many foods — especially the foods eaten most often — the more likely explanation is usually not that someone has a dozen separate food problems. It is that the gut barrier is letting more food protein reach the immune system than it should. That process is covered in leaky gut, without the hype. Dysbiosis, an overgrowth like the one in our piece on SIBO, poor protein digestion from low stomach acid, and chronic stress can all contribute.

That is why we rarely stop at avoidance. Removing reactive foods can calm things down, but if the gut problem underneath is not addressed, new sensitivities tend to appear and the list keeps growing. Addressing the gut is what gives foods a real chance to return. We don’t mask symptoms — we look to address the underlying issues that cause symptoms and dis-ease.

Where to start

If you react to food and are not sure which of these categories you are in, the first step is sorting that out: the timing and type of your reactions, your history, and whether anything points to allergy or celiac that needs to be handled elsewhere first. From there we decide whether a sensitivity panel, a stool panel, or neither is the right next step, and build an elimination and reintroduction plan around the results. If you would like help with that, reach out.

The journal is written by Dr. Nazzar from the practice. Articles reflect clinical observation and current research, not personalized medical advice. To explore your own case, schedule a consultation.