When we mention histamine, the first word that comes to mind is allergy – however, is it always so and what are all its functions?
Histamine is an amine (an organic nitrogen compound) produced by the immune system cells (mast cells, basophils and eosinophils) involved in the inflammatory immune response to an injury or foreign compounds.
The normal inflammatory response is a healing mechanism that increases the permeability of capillaries (small blood vessels) to white blood cells so they can combat the pathogens or toxins present. Histamine is also a neurotransmitter in the central nervous system (i.e. it relays messages between cells) where it is involved in many brain functions such as arousal, pituitary hormone secretion, suppression of eating and cognitive functions. So we very much need histamine for the body to function well on many levels.
The highest concentrations of histamine in the body are found in the tissues most exposed to the outside world such as the skin, mouth, sinuses, digestive tract and the lungs. Histamine is also released in the body as part of an allergic reaction, causing the typical ‘itching, sneezing, wheezing, swelling’ allergy symptoms.
Enzyme diamine oxidase (DAO) breaks down histamine and maintains a histamine balance in the body. However, some people have a low level of this enzyme, and when they eat too many histamine-rich foods, they may suffer ‘allergy-like’ symptoms such as hives, headaches, rashes, itching, diarrhoea and vomiting or abdominal pain.
There are 4 types of histamine receptors known and newer drugs are designed to primarily affect one type of histamine receptor to decrease side effects. The allergy medications, Claritin, Allegra etc., primarily block the H1 histamine receptor, which stimulates the membranes, respiratory and organ muscles, skin (itch) and the central nervous system (brain and spinal cord). Other medications, such as stomach acid inhibitors, block the H2 histamine receptors primarily, decreasing stomach secretions, including digestive acids. The other histamine receptors, H3 and H4, decrease other neurotransmitters, such as serotonin, norepinephrine and acetylcholine, and stimulate the immune T cells (thymus), spleen (lymph system), and bone marrow (blood cell production). All antihistamine medications work at all histamine receptors. Types of antihistamines developed to primarily target specific types of histamine receptors do not have their actions confined to this type alone. This is why antihistamine medications have such a variety of side effects.
As mentioned above, histamine is not only produced in the body but is also occurs naturally in many common foods. Microbial fermentation in the food converts the amino acid histidine present in high-protein foods to histamine. As such, histamine content of food increases over time as the food ages.
Histidine is also produced by some of the species of bacteria found in the gut. If they proliferate too much due to the gut flora imbalances (also known as gut dysbiosis or SIBO – small intestine bacterial overgrowth) they produce too much histamine and the symptoms appear.
This is one of the reasons why histamine intolerance is on the rise as an effect of alterations to our microbiota (gut flora) over the past 20 years or so, due to the changes to our diet including a significant increase in processed and packaged foods that are stored for a long time, use of additives and preservatives as well as pesticides and chemicals.
Therefore, an integrative approach to health in contemporary medicine is essential, which involves paying attention to the positive experience of traditional methods which perceive the organism holistically, that is, as the harmony between mind, body and emotions.