The role of histamine in the human body

Histamine_123RF33041482_blogMany are familiar with the word histamine, in the sense of antihistamine drugs that are taken by millions of allergy suffers around the world. In a very general sense these drugs work by blocking the compound known as histamine that our bodies produce during an allergic reaction. This in turn controls common symptoms such as sneezing, runny nose, and itchy, watery eyes that those with allergies suffer from.

All that being said, it is the complex role of histamine in the human body that plays a very useful and important part in scientific testing because the detection of histamine indicates the presence of foreign pathogens like allergies.

According to an article from News Medical, histamine was first discovered when it was isolated in plants by English scientists George Barger and Henry H. Dale in 1910. A year later, the two were able to isolate it in humans and discovered that histamine is found in nearly all tissues of the human body and primarily stored in tissue of the immune system.

The purpose of these tissues is to mediate inflammatory responses, meaning they locate and eliminate injurious agents that they believe are dangerous to the body. What is interesting is that these “intruders” are typically not harmful to the human body, like pollen for example, but are only believed to be so, and thus invoke an immune response, in this case known as an allergic reaction.

Because the immune system is trying to get rid of the intruders, this reaction consists of changes in blood flow, an increase in permeability of blood vessels, and the migration of fluid, proteins, and white blood cells, as described in the same article. It is these factors that cause the symptoms you feel when you experience allergies like a runny nose, itchy, watery eyes and increased mucus production— leading to congestion and sneezing. Again, this is where antihistamine comes into play, as they are taken to block the histamine being released and reduce the symptoms of an allergic reaction.

Concentrations of histamine in blood and urine are normally very low, so when scientists detect large amounts of histamine through a sample, they can determine an immune response is occurring and thus foreign pathogens are present. This type of research is often conducted by those in the biomedical fields.

Histamine is also naturally occurring in some foods including aged cheese and meats, spinach, tomatoes, bananas and citrus fruits, avocados, sauerkraut and yeast-containing foods. While many do not have to be concerned about the histamine levels of foods, a recent article suggests that some people can actually suffer from histamine intolerance, meaning they are unable to effectively metabolize histamines after they are consumed.

The article states that in the central nervous system, histamine is metabolized by histamine N-methyltransferase (HMT), while in the digestive tract it is broken down differently by diamine oxidase (DAO). DAO is the major enzyme involved in histamine metabolism and “is responsible for ensuring a steady histamine level required for the balance of numerous chemical reactions taking place in the body.”

Some individuals have altered DAO production due to genetics or a number of different factors including small intestinal bacterial overgrowth (SIBO) or copper and B6 deficiency, causing histamine intolerance.

Seen in approximately 3% of the population, histamine intolerance results in symptoms common to an allergic reaction and also includes redness or rashes, eczema, and mood or blood pressure changes after the consumption of foods high in histamine. According to the article, in up to 20% of histamine intolerance cases, the symptoms occur mostly when histamine-containing foods are consumed in combination with DAO inhibitors such as alcohol. “Approximately 80% of individuals with histamine intolerance are women and most of them are over 40.”

Because of this, a doctor interview by Fox News suggests that those with histamine intolerance (or those that think they may be histamine intolerant) should restrict their consumption of foods high in histamine and start a food diary to keep track of what they eating and the symptoms that develop. Eliminating foods containing histamine can help the symptoms go away, the article states.

Research on histamine intolerance in still ongoing along with research on potential new allergy drugs that would not only block histamine during an allergic reaction, but also other enzymes that are released as well. Some of these drugs are already in clinical trials and according to a recently published study in The Journal of Allergy and Clinical Immunology, they could help allergy suffers when antihistamine drugs are not enough to alleviate their symptoms.

For more information on Neogen’s histamine detection kits, click here.

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