Almost everyone has heard of anti-histamine, but do you know what histamine is?
Histamine is a chemical neurotransmitter that is released by cells in response to injury and in allergic and inflammatory reactions. Histamine is synthesized from histidine (an amino acid) by an enzyme named histidine-decarboxylase (HDC). It is then either stored, used in activating a receptor, or is broken down. Histamine is stored primarily in special cells called mast cells. These are found in abundance around areas prone to injury, such as blood vessels and extremities. Histamine is also stored in a type of white blood cell found in the blood stream called basophils. Histamine from these sources is part of your body’s immune system where Immunoglobulin E, part of the immune response, stimulates the histamine release. These events are triggered by bacteria or a virus, pollen or an allergic reaction.
Conditions and Body Functions That Release Histamine
- Tissue injury will cause the immediate release of histamine from mast cells.
- Allergic reactions: In allergic reactions, individuals who are allergic to certain foods like shellfish or peanuts, the body can release large quantities of histamine, which can result in shock and even death, as the body cannot tolerate large amounts of histamine. An excess of histamine in the body is referred to as histaminosis. The body will counter-act histamine by producing Epinephrine (adrenaline) which helps to de-activate histamine. For those with a true allergy, an EpiPen® administers epinephrine which counteracts the histamine reaction.
- Drugs and other foreign compounds including morphine, dextran, antimalarial drugs, dyes, antibiotic bases, alkaloids, amides, penicillin, tetracycline, venoms, and more can activate or release histamine.
- In digestion histamine plays a role in gastric secretion by helping to induce the production of acid in the stomach.
- In sleep the body regulates the amount of histamine in circulation and maintains balance. Antihistamines are known to cause drowsiness and sleep.
There are four histamine receptors: H1-H4. I won’t go into great detail about those, but wanted you to be aware that there are various histamine receptors.
Exogenous means from the outside:
Besides the histamine that they body manufactures, histamine is a component of many foods and drinks. Histamine increases as food ages or perishes, e.g., aged cheeses, fermented foods, wine and meat, poultry and fish that is not consumed or flash frozen immediately after slaughter. Histamine cannot be removed from food by freezing or cooking. Studies have shown that reduction of both the symptoms of histamine intolerance and the severity score of Eczema, also known as atopic dermatitis (SCORAD), has been shown in a subgroup of patients with Eczema and low DAO activity who were following a histamine-free diet for two weeks.