Histamine Definition - What is Histamine?

Histamine is a chemical that is normally present in tissue mast cells and certain white blood cells circulating in the body.

Histamine is involved in the immune system, digestion system and central nervous system.

Histamine as a neurotransmitter communicates important messages from the body to the brain, and it is also a component of stomach acid, which is what helps us in breaking the food in our stomach.
Large amounts of histamine are released in response to an injury or in conjunction with an antigen-antibody reaction, such as an allergic reaction.
Histamine causes contraction of pulmonary smooth muscle (bronchocon-striction) that results in an asthma-like disorder.
Histamine also dilates small blood vessels and increases their permeability.
These actions are responsible for histamine headache and the typical wheal-and-flare allergic skin reaction.
Histamine is a potent stimulant of acid secretion in the stomach.
Epinephrine and H1-receptor blocking antihistamines reverse the actions of histamine on smooth muscles;
H2-receptor blocking antihistamines, such as cimetidine or ranitidine, reverse the gastric acid stimulant action of histamine.

Histamine Intolerance Symptoms

All people have an enzyme (diamine oxidase) which breaks down any histamine that we absorb from a histamine-containing food.
When normal person eats food which contains histamine, it does not affect him. However, some people have a low level of the diamine oxidase enzyme. When these people eat too many histamine-rich foods, they may suffer ‘allergy-like’ symptoms, called Histamine intolerance.

Some of the Histamine Intolerance Symptoms, include:

• Abdominal pain,
• Flatulence,
• Diarrhoea,
• Headache,
• Pruritus (itching),
• Blepharedemas (puffy eyes),
• Urticaria (hives),
• Runny nose when eating bananas, avocados, or eggplants
• Itchy tongue
• Menstrual cycle problems
• Respiratory obstruction (difficult breathing),
• Tachycardia (racing heart),
• Extrasystoles (palpitations)
• Low blood pressure

How can the adverse effects of histamine be treated or prevented?

The most rapidly effective treatment is epinephrine (adrenaline), which is usually given by injection. Antihistamines are better at preventing reactions than treating them and are useful if an allergic reaction, such as hay fever, is expected.