Allergy
An allergic reaction is an excessive defense mechanism against an allergen, which is an external substance identified as dangerous by our immune system.
When an unknown substance enters our body, lymphocytes are activated, cells that release immunoglobulin E, which are antibodies that must analyze the new substance in order to recognize it in case of future contact.
What happens during an allergic reaction?
The immunoglobulins that have come into contact with the allergen attach themselves to mast cells, the first to face substances entering the body. When the new allergen appears again, the immunoglobulins bound to mast cells recognize the allergen and cause them to release various substances including histamine.
The role of histamine
When an allergic reaction occurs, the defensive response is excessive and can cause skin reactions with redness and itching, increased nasal and tear secretions, and in severe cases bronchial constriction and anaphylactic shock.
What does an allergic reaction involve?
Histamine has different roles and properties, including:
- It is vasodilatory
- It increases permeability
An increased blood flow means an increase in the flow of all cells involved in immune defense, such as white blood cells. This copious flow, as mentioned before, triggers the release of histamine which helps the body defend against foreign elements.
Note: I kept the medical terms “vasodilatory” and “permeability” as they are standard medical terminology in English, though in a more general health article you might want to add brief explanations of these terms.
Increased Secretion
Easily noticeable in case of allergies, which are often characterized by runny nose and increased tear production.
Smooth muscle Contractioni
In the stomach, there is contraction and release of hydrochloric acid, therefore causing stomach acidity, while in the intestines, for the same reasons, diarrhea may occur.
In the respiratory system, there is bronchial constriction and excessive bronchial secretion, which in more severe cases of allergies, causes breathing difficulties due to reduced oxygen exchange at the alveolar level.
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