Histamine Intolerance

Histamine Intolerance is a condition that can cause irritating allergic reactions caused by the "“disequilibrium of accumulated histamine and the capacity for histamine degradation” (Deutsches Ärzteblatt International journal). Patients don’t actually become overly sensitive to histamine, they just have too much of it. Several factors contribute to the body accumulating high levels of histamine, most of which relate to the molecule failing to be broken down effectively. Histamine intolerance testing may involve assessing the patient's ability to break down histamine.


Histamine Intolerance often goes hand-in-hand with Mast Cell Activation Syndrome or MCAS. Mast cells release histamine, which is necessary to fulfill vital physiological functions. Histamine is both produced in the body and absorbed from foods in various quantities. Problems only occur in cases of excessive histamine intake or poor metabolism (inadequate degradation of histamine). In these cases, histamine may lead to allergic reactions.


The following are the two main enzymes in the body that degrade histamine:

  • N-methyltransferase (HMT), which deals with histamine in the central nervous system (CNS).
  • Diamine oxidase (DAO), which is responsible for breaking down histamine ingested in foodstuffs.


Histamine intolerance is for the most part due to a (temporary) deficiency or an inhibition of the enzyme Diamine oxidase (DAO). DAO is the enzyme responsible for the degradation of histamine. Although DAO is found throughout most of the body, the bowels are its most important point of action. The enzymatic activity of DAO determines the rate of degradation of histamine. If a DAO deficiency and/or inhibition is present, the organism will not be able to degrade histamine quickly enough, and the symptoms of histamine intolerance will emerge.


Histamine Intolerance Symptoms

When the body reaches abnormally high levels of histamine, which are beyond the body’s ability to degrade, many different symptoms may occur including many that are considered to be allergic reactions. If many of these symptoms sound familiar, it may be that you want to check for histamine intolerance.

  • Abdominal cramps
  • Abnormal menstrual cycle
  • Anxiety
  • Breathing problems
  • Conjunctivitis (pink eye)
  • Difficulty falling asleep / overstimulation
  • Digestive disturbances
  • Dizziness or vertigo
  • Fatigue
  • Flushing
  • Headaches or migraines
  • Acid reflux
  • Hypertension (high blood pressure)
  • Hypotension (low blood pressure)
  • Itching
  • Nausea and/or vomiting
  • Nasal congestion
  • Sinus issues
  • Sneezing
  • Tachycardia (rapid heart rate)
  • Temperature dysregulation
  • Tissue swelling / inflammation
  • Urticaria (hives)

Such a broad range of symptoms often results in patients being diagnosed with any number of other conditions prior to histamine intolerance even being considered. For many individualls, an accurate diagnosis can take a frustratingly long time, often leading to patients scouring the internet in an effort to understand what is happening to them.


Histamine DAO Test


Testing for Histamine intolerance and DAO activity

This test is based on a radio immuno assay (RIA) principle. The determination of the DAO activity is achieved by determining the concentration of a reaction product. Radiolabeled putrescine is used as substrate. The reaction product is radioactive 1-pyrroline, which is transferred into an organic solvent by means of liquid phase extraction. After adding scintillator, radioactivity is determined by a beta counter. The quantity of radioactivity measured is directly proportional to the DAO activity of the sample.


Histamine is broken down in the body via the enzyme DAO (diamine oxidase) and histamine N-methyltransferase. The newly developed THAK test determines the total histamine degradation capacity,  regardless of which degradation pathway is relevant. By this, it has clear diagnostic advantages against  measurement of DAO activity or DAO concentration. Current research shows that THAK is independent of dietary histamine content and delivers reliable results under a histamine elimination diet.


Test type:

Immune system: Allergy, histamine intolerance, DAO deficiency


Sample required:

Serum - centrifuged. Keep at room temperature.


Average processing time:

21 ±5 days


Price (valid at July 2021):

£175  (plus shipping and phlebotomy costs)


Please refer to sample report at end of page for further information.



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Histamine.DAO Test Sample Report
Histamine.DAO sample report.pdf
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