When your stomach swells after a meal.

With an allergy, the immune system reacts to a protein in the food, usually within minutes to a few hours. With an intolerance, an enzyme is missing or weak, or a substance is poorly absorbed. The reaction is slower, often only after hours, and depends on the amount. That is why many people tolerate small portions without trouble.

By the repetition. Keep a simple diary for two weeks: what, when, how much, and which symptoms followed and when. If a pattern emerges, that is the best starting point for an analysis and for the conversation.

The usual options are DAO activity in blood, histamine in stool and histamine in blood. Each of these values has its limits: there is no single conclusive test and no agreed cut-off values. The values are looked at together with what you have noticed, not on their own.

Because it measures directly what happens in the gut. You drink a defined amount of lactose or fructose. If the sugar is not absorbed in the small intestine, bacteria in the large intestine break it down, producing hydrogen that is breathed out through the lungs. If the breath value rises clearly above the fasting value, that points to an intolerance.

Yes. You get the test solution, the tubes and a timetable. You breathe into the first tube while fasting, drink the solution and repeat at fixed intervals over about two to three hours. The tubes then go to the laboratory together.

It measures IgG antibodies against food components. Whether raised IgG values cause symptoms is disputed among specialists: several allergy societies consider the test unsuitable for diagnosing an intolerance, because IgG is also found in people with no symptoms. In functional practice it is nonetheless used as a pointer for a temporary elimination phase. You should know this before you order.

The gut barrier has a say in what passes from the gut into the body. Markers such as zonulin and I-FABP are used to gauge barrier function. Histamine is also broken down largely in the gut lining. That is why, with persistent symptoms, both are often looked at: intolerance and gut status.

Yes, and it decides how meaningful the result is. For breath tests: fast for at least twelve hours, and avoid gassy or high-fibre foods the day before. If coeliac disease is suspected, gluten must not be left out beforehand, or the test comes back falsely negative. Certain medicines affect the DAO measurement. The exact notes are included with every kit.

Stool and urine samples are straightforward from toddler age. Breath tests require the child to breathe out into a tube in a controlled way, which usually works from about six. A fingertip blood sample is possible from four, but should be talked through with the child. If in doubt, settle it beforehand in the initial consultation.

No, not on your own and not permanently. An unnecessarily restricted diet can itself lead to deficiencies, especially in children. A value that stands out is a reason for a conversation, in which the elimination phase, its length and reintroduction are planned.

The result is ready 7 to 21 days after the sample arrives at the laboratory. The lab report is then available in the Evi app. Evi stores and displays; a human does the interpretation.

That happens, and it is useful information. Complaints after eating can also come from the amount, the speed, the make-up of a meal, from stress or from the gut flora. Gut analyses or a different angle are then the sensible next step.