Histamine is an organic nitrogenous compound which is made from an amino acid (histidine). Its chemical formula is C5H9N3. Histamine is stored within most bodily tissue, but mainly in mast cells and basophils, and released as part of the body’s natural immune response to the presence of invading bodies.
When a person comes into contact with an allergen, such as pollen or animal dander, the immune system mistakenly believes that this substance to be harmful to the body and in an attempt to protect itself, Histamine is released to help the body deal with the irritation caused by the allergen. It acts as a messenger, travelling to the site of irritation to activate a response in that area of the body. It causes capillaries to dilate and become more permeable to white blood cells and other proteins, which proceed to target and attack foreign bodies in the affected tissue. The histamine released actually causes irritation and allergic symptoms in the person’s eyes, nose, throat, lungs, skin, or gastrointestinal tract. When Histamine is released into the lungs, it causes the air passages to become constricted rather than dilated. This is the body’s attempt at preventing the allergenic particles from being inhaled, but it can cause breathing difficulties.
The allergic reaction a person experiences depends on the amount of histamine released. This varies from individual to individual. For minor allergic reactions, Antihistamine medications help by preventing the release of histamine from the mast cells and basophils , thereby blocking the allergic reaction.
In cases of severe allergy, the sudden release of histamine can result in anaphylactic shock which can be fatal. In the event of an extreme allergic reaction, adrenaline is administered to eliminate histamine from the body.