What are the three different things called a food reaction?

An IgE allergy, which is immune and testable. An enzymatic or absorptive intolerance, such as lactose, which has a breath test. And mediator release, where mast cells respond to something that is not an allergen. Same words, three mechanisms, three different investigations.

I react to almost everything. What does that suggest?

Reacting to a very wide and shifting range of foods is more consistent with a mediator or handling problem than with many separate allergies, because true IgE allergies are usually few, stable and specific. That is a pattern worth reporting, not a diagnosis.

Are IgG food sensitivity panels useful here?

Major allergy bodies do not endorse them for diagnosing intolerance. IgG to a food reflects exposure rather than reaction, so a panel tends to flag whatever you eat most, which produces a long list that feels like an answer and largely describes your diet.

Does an elimination diet answer the question?

Not on its own, and a broad one actively destroys the evidence. Removing many foods at once tells you something among them mattered. Since all three mechanisms improve when you remove the food, improvement does not identify which was involved.

Is it MCAS or a food intolerance?

By B. Gray Randolph · Updated August 5, 2026

One word is doing three jobs here, and the reason people get stuck is that the word hides the difference.

What actually separates them

Three mechanisms share the phrase food reaction. An IgE allergy is immune and testable. An intolerance is enzymatic or absorptive, like lactose, and has a breath test. Mediator release is mast cells responding to something that is not an allergen. Same words, three mechanisms, three different investigations, and only two of the three have accepted tests.

The pattern that carries the most information

Reacting to a very wide and shifting list of foods is more consistent with a mediator or handling problem than with many separate allergies. True IgE allergies are usually few, stable and specific, so a list that grows and changes month to month is a different shape of problem. That is a pattern worth reporting, not a diagnosis.

We are being careful with the wording because this is exactly the observation that gets turned into a confident claim elsewhere. It narrows the field. It does not close it.

Why the popular test does not help

Broad IgG food sensitivity panels are not endorsed by major allergy bodies for diagnosing intolerance. IgG to a food reflects exposure rather than reaction, so the panel tends to flag whatever you eat most often. The result is a long list that feels like an answer and is substantially a record of your diet.

What is not settled here

Where a food-triggered mediator response ends and a food intolerance begins is not cleanly defined, and clinicians disagree. Histamine complicates it further, since some foods carry it and some mediator responses release it, so the same meal can produce the same symptom by two different routes. Nobody can currently apportion that in an individual.

Why eliminating everything makes this harder

All three mechanisms improve when you remove the food. So a broad elimination that helps tells you something among the removed foods mattered and nothing about which mechanism was involved, while making a structured investigation much harder.

Sanchez-Perez S et al., Nutrients 2021 Peer-reviewed study

It is also worth knowing how well-founded the popular lists are. Across ten published low-histamine diets, 68% of excluded foods showed no significant histamine content, and citrus was excluded by 60% of them despite none being detectable.

What to do next

Get the testable things tested. IgE allergy has established testing; lactose and fructose malabsorption have breath tests with published protocols. Excluding those narrows the field considerably before anyone reaches for a label that has no test at all.

Common questions

What are the three different things called a food reaction?: An IgE allergy, which is immune and testable. An enzymatic or absorptive intolerance, such as lactose, which has a breath test. And mediator release, where mast cells respond to something that is not an allergen. Same words, three mechanisms, three different investigations.
I react to almost everything. What does that suggest?: Reacting to a very wide and shifting range of foods is more consistent with a mediator or handling problem than with many separate allergies, because true IgE allergies are usually few, stable and specific. That is a pattern worth reporting, not a diagnosis.
Are IgG food sensitivity panels useful here?: Major allergy bodies do not endorse them for diagnosing intolerance. IgG to a food reflects exposure rather than reaction, so a panel tends to flag whatever you eat most, which produces a long list that feels like an answer and largely describes your diet.
Does an elimination diet answer the question?: Not on its own, and a broad one actively destroys the evidence. Removing many foods at once tells you something among them mattered. Since all three mechanisms improve when you remove the food, improvement does not identify which was involved.
What is worth doing first?: Getting the testable things tested. IgE allergy has established testing and lactose and fructose malabsorption have breath tests with published protocols. Confirming or excluding those narrows the field before anyone reaches for a contested label.