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Understanding Allergic Reaction and Antihistamines

Mar 09, 2023

The allergic reaction is a physiological process of the body to protect itself against external aggressions: " allergens ". Histamine released by the immune system induces an inflammatory defense response. Sometimes, the mechanism gets carried away and the severe allergic reaction is triggered. We review in this article the mechanism of action of allergy and its treatments.

The role of histamine in the allergic reaction?

Histamine is a substance produced by cells of the immune system, called mast cells, in response to the presence of a foreign substance in the body, such as an allergen. Allergens are harmless substances to most people, but for people with allergies, the immune system recognizes them as a threat and triggers an inflammatory response.

Mast cells release histamine

When mast cells are exposed to an allergen, they release histamine into the body. Histamine then binds to histamine receptors on target cells, such as smooth muscle cells in the lungs, skin cells, and cells in the nose and eyes. This binding causes an increase in the permeability of blood vessels, which allows immune system cells to more easily penetrate surrounding tissues. This can cause inflammation, which manifests as redness, swelling, and pain .

Abundant production of mucus

Also, histamine stimulates glands that produce mucus in the nose and lungs, which can lead to nasal congestion and difficulty breathing. Histamine can also cause itching and rashes. In short, histamine triggers an allergy by triggering an exaggerated inflammatory response of the immune system to the presence of an allergen in the body.

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What is an antihistamine?

An antihistamine is a type of medicine that is used to treat allergy symptoms . Allergies are a reaction of the immune system to foreign substances like pollen, dust mites, mold, animal hair, etc. This reaction causes the release of a substance called histamine, which can cause symptoms such as itching, sneezing, itchy eyes, rashes, and nasal congestion. Antihistamines work by blocking the effects of histamine in the body, thereby reducing allergy symptoms. They can be taken orally, as tablets or syrups, or applied topically as creams or gels. Antihistamines are usually available over-the-counter, but some stronger types may require a doctor's prescription.

The allergic reaction, a normal and physiological response of the body.

Indeed, the allergic reaction is in fact a normal and physiological response of the body . The immune system is designed to protect the body against foreign invaders such as bacteria, viruses and parasites, and it is able to recognize foreign substances such as allergens.

In an allergic response, the immune system overreacts to a harmless substance, such as an allergen, and triggers an inflammatory reaction to eliminate the substance. This reaction is characterized by the release of inflammatory mediators such as histamine, which cause symptoms such as itching, rashes, sneezing, nasal congestion and difficulty breathing. Although the allergic response is a normal body response, it can be very uncomfortable and potentially dangerous in some cases, such as severe allergic reactions (anaphylaxis) . Antihistamine medications are often used to treat allergy symptoms by blocking the effects of histamine in the body.

The discovery of antihistamines

Antihistamines were discovered in the 1930s, by a French pharmacologist named Daniel Bovet .

At the time, it was already known that histamine played an important role in allergic and inflammatory reactions, but there was no drug to block its effects. Bovet began its research by studying the effects of histamine on animal tissues, in particular the intestines and blood vessels. He found that histamine caused the smooth muscles of the intestines to contract and the blood vessels to dilate, leading to lower blood pressure.

Bovet then began looking for compounds that could block the effects of histamine. He tested many compounds, some of which were already used for other diseases, and finally found a compound that was effective in blocking the effects of histamine without having significant side effects. This compound was pyrilamine, the first antihistamine ever discovered.

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Lieberman, Phil. “The Basics of Histamine Biology”. Annals of Allergy, Asthma & Immunology: Official Publication of the American College of Allergy, Asthma, & Immunology 106, No. 2 Suppl (February 2011): S2-5. https://doi.org/10.1016/j.anai.2010.08.005.

Muche-Borowski, Cathleen, Matthias Kopp, Imke Reese, Helmut Sitter, Thomas Werfel, and Torsten Schäfer. “Allergy Prevention”. Deutsches Arzteblatt International 106, No. 39 (September 2009): 625 31. https://doi.org/10.3238/arztebl.2009.0625.

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