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All About Histamine Intolerance

29th June,  by Flora Crichton 

What is histamine, exactly?

The name “histamine intolerance” might make it seem as if it’s a negative thing. Yet, histamine is really crucial to our health and well being. Histamine is a chemical made by our immune system. It is released in response to an injury or allergen entering the body.

When we come into contact with an allergen or intolerance, histamine acts throughout the body. It will release adrenaline, spike our heart rate, cause our lungs too constrict, and our capillaries can increase in size. Swelling occurs, which may cause the skin to itch. We are experiencing an allergic reaction. We are not actually allergic to histamine. Histamine intolerance occurs when undesirable symptoms arise as a result of too much histamine accumulating in the body. We often use a bucket analogy in Nutritional Therapy; when there is too much histamine in the bucket, the bucket will spill its contents and hence, we experience symptoms.

Histamine was first described in the 1960’s, after people were suffering from the symptoms of excessive histamine ingestion. It was initially referred to as scombroid fish poisoning, because it was associated with fish consumption. Fresh, canned or smoked fish can reach high histamine levels; if it has been improperly processed or storaged, it will accumulate bacteria.

Why might too much histamine accumulate in the body?

Histamine accumulation can result from an inability of the body to break it down, especially when it's in excess. Our body produces a digestive enzyme called Diamine Oxidase (DAO), which breaks down histamine and is heavily present in our gut. We can experience a deficiency in this enzyme, due to various factors:

  1. Gut inflammation, leaky gut, infections, SIBO, bacterial overgrowth. It is worth seeking Nutritional Therapy if you experience high histamine and gut issues, as a good quality stool test can give you some answers; particular bacterial strains in our gut can increase histamine production. So, it’s important to learn how to decrease these bacterial strains and repopulate the gut with more beneficial strains.

  2. Alcohol contains histamine and nicotine from cigarettes increases histamine production also. So, a heavy smoker or drinker may suffer from excess histamine symptoms.

  3. Certain medications block DAO enzyme function e.g. antibiotics, antidepressants, gastrointestinal medicines, anti-arrhythmic (which treat heart rhythm irregularities), antihypertensives (which treat high blood pressure) muscle relaxants, narcotics and local anaesthetics.

  4. Eating a high histamine diet. Many foods contain histamine or liberate histamine in the body.

  5. A highly stressed person may also struggle to adequately break down histamine, because DAO enzyme requires Vitamin B6. This vitamin is also needed to break down adrenaline, produced when the body is under stress.


Having too much histamine in the body can give rise to unwanted symptoms….


  • Eczema

  • Hives

  • Asthma

  • Headaches

  • Swelling

  • Flushing

  • Itching

  • Watering eyes

  • Runny nose

  • Digestive issues

  • Heart palpitations

  • Period pain

  • Anxiety

  • Insomnia


Why might too much histamine accumulate in the body?


Our DAO enzyme protects us against histamine coming into the body from outside. It is present in high amounts in our gut,  so DAO will break down histamine from ingested food. Histamine may be produced as food begins to spoil or ferment. For example, kefir, sauerkraut, aged cheese, soya sauce, dried fruit, tinned or smoked fish and meats. Some foods are histamine liberator foods, meaning the body produces histamine once they’re ingested. Kiwi, citrus, tomatoes and avocado, alcohol, bananas, some nuts (especially walnuts, cashews and pecans) chocolate are all histamine liberator foods. Prawns and other shellfish tend to be histamine liberators and are prone to rapid histamine formation. Upon exposure to pollen, dust mites, pollution (petrol fumes), Xeno-estrogens (in plastics)  and chemicals , our body will also release histamine. Excess alcohol/green or black tea may cause histamine to build up in the body, because these suppress DAO enzyme activity, our enzyme that breaks down histamine.



Are histamine excess symptoms more prevalent in women?



There is the belief that a hormonal interaction exists between histamine and hormones.  This is because atopic disease, eczema, hay fever and asthma are more common in women. Oestrogen hormone actually encourages the breakdown and release of histamine, whilst at the same time inhibiting DAO enzyme activity. So, anyone with oestrogen dominance may struggle to break down histamine effectively, and so are more likely to suffer from high histamine levels. You are likely to be oestrogen dominant if you suffer from heavy periods, period pain, PMS and/or breast tenderness. Exposure to histamine at the start of your menstrual cycle can exacerbate menstrual pain, menstrual migraines and allergic symptoms.


During pregnancy, histamine levels are suppressed. In order to protect the baby from excessive histamine entering the foetal circulation, DAO enzyme production is increased by 500 times! The mother is therefore able to avoid allergic symptoms during pregnancy, but unfortunately, symptoms usually reoccur post partum.


So, histamine intolerance is commonly assumed to be due to histamine ingestion exceeding our capacity to break it down. Whilst exposure to foods high in histamine or foods that stimulate histamine release may be the final straw in triggering allergic symptoms, it is unlikely to be the sole root cause. The same applies to genetics. DAO enzyme deficiencies are strongly associated with symptoms, but not everyone with these gene variances develops histamine symptoms, and not everyone with histamine intolerance has under performing DAO genes. The functional medicine model enables diagnosis of complex conditions, that might have many causes and many symptoms. It strives to recognise the connection between genes, nutrition and lifestyle.

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