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Histamine and histamine intolerance (HIT) – an exciting topic that will be discussed in more detail below.

Allergy sufferers, such as those suffering from hay fever, know the antihistamines that provide relief from their allergic symptoms during pollen season.

But it's not just pollen that can trigger histamine releases in the body and lead to an excess of histamine; other factors, such as diet or a lack of production of histamine-degrading substances, can also cause histamine levels to be too high.

Histamine – what is it?

Histamine (ancient Greek ἱστός histos = tissue) is a biogenic (ancient Greek βίος bios = life and genesis = emerging) Amine (organic derivatives (descendants) of ammonia (NH3)), which as a tissue hormone occurs predominantly in the skin, lungs, stomach, intestines and diencephalon.

Biosynthesis and storage

Histamine is synthesized in mast cells, epidermis, gastric mucosa and nerve cells and stored in vesicles bound to heparin. It is formed from the amino acid histidine through a pyridoxal phosphate-dependent decarboxylation by the enzyme histidine decarboxylase in a one-step reaction.

release

Histamine is released from, for example, mast cells, basophilic granulocytes, cells of the bronchi, mucous membranes and the gastrointestinal tract (whose ECL cells produce histamine from gastrin, acetylcholine and PACAP (pituitary adenylate cyclase activating polypeptide) release) due to IgE-induced allergic reactions of the immediate type (type I) or complement factors (the complement system is part of the non-specific humoral immune system (related to antibodies and other defense-active proteins).

Externally provoked release

The following pharmaceuticals can contribute to increased histamine release:

• Muscle relaxants
• opiate
• Plasma expander
• X-ray contrast media

Foods also contain different concentrations of histamine.

Due to the distillation process, essential oils do NOT contain histamine!
Therefore, suggestions found in the media that one should avoid essential oils such as orange or lemon when using HIT are baseless and therefore unfounded.

Essential oils are obtained by distillation with water or ethanol (which is removed after distillation). Histamine is soluble in water and ethanol (source), but not in ether, would therefore remain in solution. The essential oil does not contain any histamine.

Functionality

The main function of histamine is its involvement in the defense against allergens or foreign substances.
Viewed at the cellular level, histamine initiates H through the activation of histamine receptors₁ .. H₄, – which in turn belong to the G protein-coupled receptors, which are responsible for transmitting extracellular signals into the cell (via G proteins) – the defense reactions.

Histamine serves as a neurotransmitter in histaminergic neurons within the CNS. The highest histamine concentration is found in the hypothalamus.

The sleep-wake rhythm is activated by activating the H₁receptor regulated. This also induces vomiting. It is still unclear how this receptor is involved in the regulation of appetite, blood pressure, body temperature and the sensation of pain.

In addition to regulating intestinal motility, histamine regulates the activation of H₂-Receptors the production of stomach acid.
The activation of the H₂-Receptors cause the heart to increase its beating force and frequency.

The presynaptic H₃-Receptors influence the effects of the neurotransmitters dopamine, glutamine, norepinephrine and serotonin.

Histamine acts as a mediator in allergies, asthma, inflammation and burns and causes the sensation of pain, leads to the contraction of smooth muscles, such as the bronchi, blood vessels (> 80 μm), digestive organs, but also skin, as well as itching and hives. In smaller blood vessels, histamine causes vasodilation, resulting in reddened skin.
Histamine also leads to the release of adrenaline, primarily through activation of H₁-Receptors, from the adrenal glands.
The activation of the H4 receptor causes the eosinophil granulocytes and T lymphocytes (thymus cells) to be alerted.

Dismantling

Histamine is broken down primarily in the central nervous system (CNS) by the enzyme histamine N-methyltransferase.
Otherwise, degradation occurs primarily via diamine oxidases and aldehyde oxidases to form imidazolylacetic acid, which is excreted via the kidneys after ribosylation.

Histamine levels

The laboratory reference range for histamine (total) i. Hep.-Bl. (ELISA) is < 65.5 ng/ml.

10 mg/ml leads, among other things, to acute shortness of breath, drop in blood pressure, diarrhea, vomiting, reddening of the skin, headaches, hives, nausea, while 100 mg/ml is considered poisoning with correspondingly increased symptoms mentioned above, as well as fainting and swelling of the face and tongue.

Histamine-boosting components

In addition to the above-mentioned pharmaceuticals, MAO inhibitors (inhibit the breakdown of the hormone adrenaline and neurotransmitters, e.g. dopamine, norepinephrine and serotonin) cause an increase in histamine in order to cause a dysregulation of brain metabolism in e.g. depression due to higher plasma levels and concentrations of the amines mentioned of the cell.

Foods with a histamine-increasing effect include: alcohol, pineapple, bananas, pears, beans, chili, strawberries, guava, raspberries, kiwi, lentils, papaya, chocolate, soy, wheat germ, citrus fruits

Histamine-lowering components

Apple, broccoli, Blueberry (wild), hibiscus tea, ginger, chamomile tea, paprika, peppermint tea, black cumin oil are among the histamine-lowering foods.

Histamine-rich foods

Foods such as eggplant, avocado, balsamic vinegar, fish (except freshly caught or freshly frozen), yeast extract, yogurt, coffee, cocoa, cheese (the riper, the more), mushrooms, red wine, sauerkraut (pickled foods, such as pickles, etc. ), sour cream, ham, soy sauce, spinach, tea, tomatoes, wine vinegar, citric acid (concentrate) are among the histamine-rich components of the diet and should be avoided with HIT.

Low-histamine foods

Foods that are low in histamine and therefore safe for HIT include: agave syrup, cauliflower, crème fraîche, spelt, egg, vinegar (apple/brandy), fennel, cream cheese, fresh milk, fruit juices, barley, kale, cucumber, long-life milk, Oats, oat milk, millet, honey, cottage cheese, cheese (young varieties), carrot, potato, herbal tea (except nettle), culinary herbs, pumpkin, pumpkin seed, turmeric, leek, linseed, macadamia, corn, almond milk, almonds, chard, chestnut, Mozzarella, pasta, peppers, Brazil nuts, parsnips, pistats, quark, quinoa, radishes, rhubarb, beetroot, red cabbage, cream, salsify, celery, sesame, asparagus, sweet potato, sweet cream butter, zucchini, sugar, onion.

All salads are also low in histamine, with one exception: arugula.

Fruit that can be classified as low in histamine includes: apple, apricot, blackberry, cranberry, dates, pomegranate, blueberry, currant, jostaberry, persimmon, cherry, lychee, mango, melon, nectarine, peach, cranberry, sour cherry, grape

Pathological aspects

In addition to the symptoms already mentioned above, the following signs of HIT are also present:

Anxiety, diarrhea, palpitations, cardiac arrhythmias, hyperhidrosis, hypotension, headaches (also migraines), conjunctivitis, panic attacks, rhinitis, rhinorrhea, heartburn, tachycardia.

An increased stomach acid level may indicate a histamine-induced defense reaction.

Laboratory medicine – differential diagnosis

Elevated blood levels of histamine can have three causes:

• Excessive release from mast cells
  – IgE-mediated allergies
  – Pseudo-allergies
  – increased mast cell activation (increased mast cell number, reduced membrane stability)
• Histamine breakdown disorder
  – primary (genetically determined) deficiency of diamine oxidase (DAO)
  or histamine N-methyltransferase (HNMT)
  – secondary lack of activity of DAO, triggered by lack of Kuofer, vitamin B6, zinc,
  Reduced DAO formation due to destroyed intestinal epithelia or drug influences
• Increased histamine formation due to increased settlement of histamine-producing bacteria in the intestine

If an elevated histamine level has been determined according to a blood test, the histamine concentration in the stool must be determined using a stool examination and the detection of histamine-producing bacteria in the stool must be carried out in order to clarify the cause using a differential diagnosis.

Histamine in stool is laboratory-referenced as < 600 ng/g (ELISA).

For this purpose, cultures of histamine producers are created. The reference values for

• Hafnia alvia
• Klebsiella pneumoniaae
• Morganella morgani

are each <= 1 x 10⁶.

(source)