Diagnosing histamine intolerance
To date there is no clear cause of histamine intolerance, and the diagnosis is therefore difficult.
Moreover, the symptoms are unspecific. Many are similar to those of a food allergy, but there are also similarities to the signs of fructose malabsorption, lactose intolerance and, to a certain extent, celiac disease.
Detailed patient history and symptom tracking
Diagnosing histamine intolerance requires a comprehensive physician's review of the patient's lifestyle, nutritional habits, and symptoms. Many doctors will ask the patient to keep a "symptom diary", which can be useful in tracking which foods are causing their symptoms. The medication a patient regularly takes can also play a role, as some can cause the body to release its own histamine.
Since the symptoms are unspecific, other diagnoses should be considered along with histamine intolerance. Allergies and mastocytosis, as well as other food intolerances, should always be ruled out first.
If, after other causes have been ruled out, the suspicion of a histamine intolerance still exists, the next step is an elimination diet followed by a provocation test (also known as a histamine challenge).
Diagnostic elimination diet
For two to four weeks, the patient should consume as little histamine as possible and keep a symptom diary. If the symptoms improve during this time, this provides evidence of histamine intolerance.
Diagnostic provocation test
A diagnosis can be confirmed by means of a final provocation test. At best, this is placebo-controlled and double blind, meaning neither patient nor tester know when the patient actually receives the histamine and when a placebo. Due to the generally high cost of these tests, however, a different approach is usually chosen, wherein the patient consumes small amounts histamine-rich food. If they detect the known symptoms from a certain histamine load, this is considered to be evidence of the histamine intolerance. Such a provocation should take place under medical supervision, as the risk of an anaphylactic shock cannot be excluded.
Other diagnostic procedures for establishing a histamine intolerance
Apart from provocation testing, it is possible to measure DAO enzyme activity in the blood, which can affect histamine levels. That being said, these tests are only conditionally conclusive.
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