Histamine diagnosis has constantly changed in recent years. HIT is a new phenomenon and new studies about it were published in order to establish a standardized diagnostic test. What we know so far is, that at the moment there are no reliable laboratory parameters to diagnose histamine intolerance.
Anyways, a hasty diagnosis of histamine intolerance should be be avoided, because the consequences could be that another illness might not be detected. The diagnosis would be delayed and irreversible organ damage might then develop.
Before you visit your physician, it is highly recommended that you keep a food diary. This will make it considerably easier for your doctor to narrow down the symptoms and their causes.
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In all cases, a differential diagnosis needs to be conducted. This means that other illnesses (inflammation, malabsorption, tumors, mastocytosis, etc.) can be definitely ruled out. This usually means an examination by an allergist, dermatologist, internist, gastroenterologist and possibly other specialists (for instance a cardiologist), depending on the main symptoms.
Since this diagnostic path requires an accurate knowledge of the histamine content of foods, this path is very difficult and must be accompanied by a medical doctor!
First, a well-planned low histamine dietary phase, including a very accurate food and symptom diary, is performed. This phase lasts 2-4 weeks. During this period, all foods with biogenic amines should be strictly avoided, no alcohol should be drunk, no DAO-blocking drugs taken (discuss with your physician) and no antihistamines should be taken.
If the symptoms improve, a HIT is very likely. Your physician should have copper and vitamin B6 tested by a blood test in this case. The DAO needs these substances to function properly. If there is too little of it, the DAO cannot be formed or cannot function properly. A substitution may improve the HIT.
Well, after this low-histamine dietary phase, you could make a provocation test, which should be performed placebo controlled and double-blinded. You will receive different liquids to drink and the reactions will be recorded. However, this is only possible in specialized clinics and hospitals, and is discouraged by some guidelines. Alternatively, you may eat histamine-containing foods (in consultation with the doctor!) and record your reactions in the food and symptoms diary. Important: Only test one food per day! For example cheese, salami, red wine or sauerkraut. The reactions should then occur within 4 hours. A severe form of histamine intolerance (which is very rare!) could lead to anaphylactic shock during the provocation test, which is why it is better not to do this without medical supervision.
Caution: Several testing kits are available on the market. Some use blood, others work with urine or stool testing. Some physicians use blood tests to determine the DAO level. However, these tests are classified as unsuitable by the specialist organizations as described above and may lead to misdiagnosis.
The most likely way to diagnose histamine intolerance was to take two blood tests at an interval of two to four weeks, introducing a low-histamine diet in between. The amount of DAO was tested to analyze if someone is histamine intolerant or not.
But, sadly, this does not work. One has also tried to establish the activity of the DAO instead of the quantity, as a diagnosis factor but only with moderate success. It has been found in recent studies that the activity of the enzymes in the intestinal mucosa is not related to the amount or activity in the blood. So these blood tests don't work.
The histamine and methylhistamine concentration in the urine can also be determined. Mehylhistamine is the degradation product of the HNMT. If a DAO deficiency is present, the histamine is degraded in the cells via the HNMT. Accordingly, the degradation product methylhistamine increases, which is excreted via the urine and can thus be determined by a laboratory within a 12 hour collection test. Then a strict potato-rice diet is kept for several days and the urine test is repeated. Doctors thought to be able to diagnose HIT by analyzing the rate of change of the results. This has turned out to be wrong. Here, too, differential diagnosis is important since this test alone is not sufficient to diagnose a histamine intolerance.
The amount of histamine can also be determined in the stool. This amount, however, only indicates how much histamine has not been degraded in the intestine or is produced by bacteria in the colon. This amount varies according to your type of food intake, and depends on the added amount of histamine. It also depends on the composition of the intestinal bacterial populations. The histamine produced by the body itself cannot be tested by this test. Therefore, this test has been considered to be unsafe for some time and therefore belongs to the outdated diagnostic pathways.
That means: Measurements of DAO or histamine via the urine or the stool are not accurate.
This test measures the immune reaction of the body's own immunoglobulin G. These types of tests are not suitable for diagnosing conditions such as lactose intolerance, fructose malabsorption or histamine intolerance!
There are some other tests on the market like bioresonance, hair analyses, spit analyses or others. None of these methods are able to diagnose histamine intolerance!
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2) Jarisch, R. "Nahrungsmittel-Intoleranz", medmix 4/2008, pp 49-52
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8) nmi-Portal (Michael Zechmann)