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Histamine Intolerance




The article was originally published on my blog https://www.mummyandchild.com


Histamine Intolerance

What is Histamine?


Histamine is an important bio-active chemical involved in your immune system, digestive system, and your central nervous system. Histamine is found in your mast cells (white blood cells). As a neurotransmitter, it communicates important messages from your body to your brain. It is also a component of stomach acid, which is what helps you break down food in your stomach. It also helps you move your bowels, pay attention and enhance exercise.

The ideal amount of histamine will allow the above functions to occur and occur perfectly. Histamine levels of 0.3 to 1.0 nanograms per millilitre (ng/mL) in plasma are generally considered to be normal and each person will have a “threshold”. Histamine levels above that will cause symptoms to start appearing. Various abnormal physiological conditions, hormone changes, medications and gut imbalance can reduce the tolerance threshold of an individual.

Histamine Intolerance (HIT)


Generally, the body is able to break down histamine naturally and there are no “excess” levels of it to cause any adverse reaction. But for some people, they are unable to break down histamine effectively in their body which translates to “histamine intolerant”.

One way to explain how this works is to use the ‘histamine bucket’ explanation. Take a look at the illustration below. When you have histamine intolerance your bucket has a lower “capacity” and therefore it gets full faster. The symptoms you see are the result of the “histamine bucket” overflow. histamine-bucket-850x471.jpgHistamine bucket effect

According to research, impaired histamine degradation is the main cause of HIT. The body metabolizes histamine via two degradation pathways (also known as catabolism)

  • Methylation by histamine-N-methyltransferase (HNMT)
  • Oxidative degradation by diamine oxidase (DAO)

HNMT works on histamine in our cells while the enzyme DAO plays a major role in the breakdown of histamine in our gut. Studies have shown that it is a lack of DAO that is responsible for HIT in most cases and has received the most attention in medical research. Under normal circumstances, this enzyme will start degrading histamine to bring it back to normal levels, whereas in HIT the rate of degradation is insufficient causing a build-up of histamine in the body leading to symptoms. DAO-Enzyme.jpgSource: https://www.ncbi.nlm...les/PMC5346110/

What Causes Histamine Intolerance?


There are a number of possible causes of this condition:

  • Genetic Mutations – Genetic mutations can predispose you to become histamine intolerant. Some individuals have impaired production of the DAO and HNMT enzymes due to genetics. Those who have an MTHFR gene mutation are likely candidates for histamine intolerance because the mutation inhibits our ability to methylate properly, a process by which many toxins, including excess histamine, is eliminated. SNPs in MAO and PEMT genes can also cause this condition. Dr. Ben Lynch is an expert in this area of study.
  • Mast cell activation disorder– Histamine lives in our mast cells (white blood cells). Mast cell activation syndrome (MCAS) is one type of mast cell activation disorder (MCAD) and is an immunological condition in which mast cells inappropriately and excessively release chemical mediators. It is usually caused by changes (mutations) in the KIT.
  • Histamine-Rich Food– Certain foods are high in histamine. The amount of histamine we consume impacts the histamine level in our body. Fermented foods, high protein intake, aged foods, leftovers, citrus, fish are naturally high in histamine. You will find detailed information about these below.
  • DAO Inhibitors – Certain foods lower DAO (the enzyme that breaks down histamine) function in the body. The food list is given below. These foods increase histamine levels by impeding DAO’s effectiveness.
  • Gut Dysfunction / Leaky Gut – When the gut wall is damaged and leaky, the body’s ability to produce DAO is diminished. Poor gut health can lead to histamine intolerance. Also, conditions such as SIBO, candida and other pathogens can block methylations and produce histamine.
  • Nutrient deficiencies – B12, folate, B6, B2, B1, Zn, Cu, C, methionine
  • Medications – antibiotics, antacids and even antihistamines (long term)
  • Nutrient demands – stress, anxiety, lack of sleep
  • Hormonal insufficiency – adrenal fatigue
  • Hormonal excess – Oestrogen



There is a broad spectrum of symptoms associated with this condition making it extremely hard to diagnose. Symptoms vary depending on the source of histamine when the total body level exceeds the enzymes’ capacity to break it down.

In some cases, symptoms are similar to an allergic reaction, but allergy tests usually come back as negative. You could experience one or many of the following symptoms after having a meal. It could be immediately after a meal or it may take a few hours or even days to surface as it could accumulate in your body. Histamine_Reactions-848x478.pngSource: https://www.ncbi.nlm...les/PMC5346110/

Most common symptoms of histamine intolerance include the following:

  • abdominal pain
  • migraines
  • irritability
  • excessive sweating when barely exercising
  • sweaty feet
  • nosebleeds
  • flushing: red face/red hot ears
  • exercise-induced asthma
  • insomnia
  • anxiety
  • dizziness
  • seasickness
  • eczema

Testing for Histamine Intolerance

  • Elimination – Remove high histamine foods for 30 days. If your symptoms resolve then you most likely have histamine intolerance.
  • Blood Testing – Certain companies offer a blood test to check for DAO If a DAO deficiency is detected you will be unable to break down histamine in your body. If testing is unavailable to you, you could simply try a diet low in histamine and add DAO supplementation at each meal. If your symptoms resolve, you could have low DAO.
  • Skin Prick testing – You can also request for a skin prick test where the positive control is a histamine-containing solution. In general, the weal size of the histamine control would reduce within 20 minutes, but in individuals who are histamine intolerant, it will be visible even after an hour.
  • Genetic testing – A genetic test such as 23andme or Ancestry could give you a good indication of the SNPs that may indicate a predisposition to histamine intolerance. However, having a predisposition means you have an increased risk of developing the condition, therefore, test results should be used along with symptoms to make a diagnosis


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