Histamine is an organic nitrogen compound involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. Histamine triggers the inflammatory response. As part of an immune response to foreign pathogens, histamine is produced by basophils and by mast cells found in nearby connective tissues. Histamine increases the permeability of the capillaries to white blood cells and some proteins, to allow them to engage pathogens in the infected tissues.
As an integral part of the immune system, histamine may be involved in immune system disorders and allergies. Mastocytosis is a rare disease in which there is a proliferation of mast cells that produce excess histamine.
FROM THE LOW HISTAMINE CHEF:
Simply: histamine is found in mast cells. It it released to help fight infection/illness/injury, keep us awake, regulate our hormones, run our digestive system and as a neurotransmitter. Some people have unstable mast cells that release too much of it, or they just have too many mast cells. Some people have allergies which means they also have too much histamine at times. Others have too little of the histamine lowering enzymes diamine oxidase (DAO) or HNMT. An excess of histamine is involved in: allergies, histamine intolerance, mast cell activation, mastocytosis and a number of other medical conditions. You’ll find a list of symptoms here. (I have MCAD/mast cell activation disorder).
Other than being found in the body, histamine is also in food! Some foods contain it, while others trigger its release. I stick to a high nutrient, low or antihistamine diet to manage my mast cell activation disorder, without any medication. For more on which foods do what see my interview with immunologist and histamine researcher Dr Janice Joneja here. Unfortunately, beauty and bath products can also trigger histamine release, more on that in the Low Histamine Beauty Survival Guide, as well as stress, vibration, altitude, chemicals and medications. You’ll find more information in the Low Histamine Lifestyle 101 Guide.
People with histamine intolerance, mast cell activation and mastocytosis may also have allergies. If they do, lowering their overall histamine could help mitigate the intensity of their allergic reactions. Many people with a histamine disorder (myself included) find that a diet low in histamine helps lower overall histamine. You’ll find a list of foods I’ve used to recover my health in the Anti-Cookbook: High Nutrient Antihistamine & Anti-inflammatory Foods for Health.
For an explanation on how allergies and histamine are different see my interview with immunologist and histamine researcher Dr Janice Joneja here.
More on histamine from Wikipedia:
ROLES IN THE BODY
Although histamine is small compared to other biological molecules (containing only 17 atoms), it plays an important role in the body. It is known to be involved in 23 different physiological functions. Histamine is known to be involved in so many physiological functions because of its chemical properties that allow it to be so versatile in binding. It is Coulombic (able to carry a charge), conformational, and flexible. This allows it to interact and bind more easily.
Histamine is released as a neurotransmitter. The cell bodies of histaminergics, the neurons which release histamine, are found in the posterior hypothalamus, in various tuberomammillary nuclei. From here, these neurons project throughout the brain, to the cortex through the medial forebrain bundle. Histaminergic action is known to modulate sleep. Classically, antihistamines (H1 histamine receptor antagonists) produce sleep. Likewise, destruction of histamine releasing neurons, or inhibition of histamine synthesis leads to an inability to maintain vigilance. Finally, H3 receptor antagonists increase wakefulness.
It has been shown that histaminergic cells have the most wakefulness-related firing pattern of any neuronal type thus far recorded. They fire rapidly during waking, fire more slowly during periods of relaxation/tiredness and completely stop firing during REM and NREM (non-REM) sleep. Histaminergic cells can be recorded firing just before an animal shows signs of waking.
While histamine has stimulatory effects upon neurons, it also has suppressive ones that protect against the susceptibility to convulsion, drug sensitization, denervation supersensitivity, ischemic lesions and stress. It has also been suggested that histamine controls the mechanisms by which memories and learning are forgotten.
Erection And Sexual Function
Libido loss and erectile failure can occur following histamine (H2) antagonists such as cimetidine and ranitidine. The injection of histamine into the corpus cavernosum in men with psychogenic impotence produces full or partial erections in 74% of them. It has been suggested that H2 antagonists may cause sexual difficulties by reducing the uptake[clarification needed] of testosterone.
Metabolites of histamine are increased in the cerebrospinal fluid of people with schizophrenia, while the efficiency of H(1) receptor binding sites is decreased. Many atypical antipsychotic medications have the effect of increasing histamine turnover.
Histamine therapy for treatment of multiple sclerosis is currently being studied. The different H receptors have been known to have different effects on the treatment of this disease. The H1 and H4 receptors, in one study, have been shown to be counterproductive in the treatment of MS. The H1 and H4 receptors are thought to decrease permeability in the Blood Brain Barrier, thus increasing infiltration of unwanted cells in the Central Nervous System. This can cause inflammation, and MS symptom worsening. The H2 and H3 receptors are thought to be helpful when treating MS patients. Histamine has been shown to help with T-cell differentiation. This is important because in MS, the immune system attacks its own myelin sheaths on nerve cells (which causes loss of signaling function and eventual nerve degeneration). By helping T cells to differentiate, the T cells will be less likely to attack the body’s own cells, and instead attack invaders.