August 8, 2007

The Mechanism Behind Allergies

Do you know how allergies work? The most obvious side of allergies and asthma encompasses the symptoms. When your eyes begin to itch or your chest feel tight, you could care less about the tiny cells that are working hard to produce your allergic reaction. Yet, understanding the steps of the allergic cascade could help you cope with future reactions.

Allergic Cascade at a glance

1. Specific allergens are identified by your body as “harmful”

2. T- and B- Lymphocyte cells create chemicals to trigger your immune system’s defenses

3. Mast cell and Basophils release chemical “mediators” that cause allergic inflammation

4. The immediate “early phase” reaction is often followed by a longer “late phase” reaction

A More Detailed Look at the Allergic Cascade

The process of developing allergic reactions takes place after exposure to a particular allergen. For certain individuals, cells develop a means of identifying the allergen and make preparation for the next encounter. Several varieties of cells in your body are responsible for defense against foreign, potentially dangerous intrusion—without these cells, your body would be overcome by illness. These play special roles in allergic reactions:

Lymphocytes – These cells are part of the white blood cell family. There are two varieties of lymphocytes: T & B.

Lymphocyte T – “helper cells” the detective of the immune system. This cell finds the evidence of foreign elements in the body. When Lymphcyte T comes in contact with the actually fragment of pollen or dander causing the problem it releases chemicals to stimulate B cells.

Lymphocyte B – these cells produce IgE antibodies after receiving the chemical warning of danger from the T cells.

What is IgE?

IgE is used to attack allergens—once it is produced, it binds itself to an element like pollen in order to protect the body. After having encountered an allergen, IgE will remember what the allergen looks like, so that the next time the allergen enters the body, IgE will be ready.

TH1 and TH2– These cells are used to combat illnesses, so when the body is in danger on a molecular level, many of these cells are produced—as if the immune system were raising an army.

TH1 – these cells are produced in cases of infections and other illnesses

TH2 – these cells are produced in cases of allergic sensitivity.

Mast Cell and Basophils – some very volatile cells with explosive behavior. These cells have over 1,000 tiny packets of more than 30 different chemicals. These chemicals are referred to as “mediator chemicals” and they are responsible for allergic symptoms like swelling, sneezing and itchiness.

Mast Cells – found in bodily tissue

Basophils – found in blood

IgE acts like the fuse to a bomb

After your immune system has come to recognize certain allergens and raise armies of TH cells to combat the invaders, it is the IgE chemical that sets off an allergic reaction. Because IgE is able to indentify the allergen as soon as it enters the body, it triggers Mast Cells and Basophils to explode, releasing histamine and leukotriene D4 (which is 10 times more powerful than histamine) and leaving you with all the symptoms associated with allergic reactions.

Two Phases of Allergic Reactions

Early Phase: “Immediate Hypersensitivity Reaction”

This “early phase” is the initial reaction—each of the cells described in the list above performs its task. It takes only a few minutes for this phase to be completed. At this point, the allergic reaction will either dissipate or continue into the “late phase”. The chances are roughly 50/50.

Late Phase: “Sensitivity Accelerant”

Half of the time, you will experience the “late phase” of an allergic reaction. Usually this phase occurs 4 to 6 hours after the exposure. Cells swarm to the site of reactions and cause further inflammation resulting in redness and swelling.

Danger of the “Late Phase”

Repeated episodes of the “late phase” reactions could cause chronic allergies or spark asthma. Also, with each “late phase”, you body becomes more and more sensitive to the allergen.

What Medications and When to Take Them

Anti-Inflammatory Medications (Steroid or Leukotriene Inhalers and Medications). These forms of medication are most effective if taken during the “early phase” of an allergic reaction. Medications that widen the airways are very effective at controlling immediate reactions.

Standard Antihistamines. It is best totake anti histamines is you are anticipating exposure to an allergen during the day (i.e. visiting a friend with a dog or cat, playing outdoor sports where pollen may be encountered, etc). Another important time when antihistamines can be helpful to slow the allergic cascade is right AFTER the “early phase”. Taking antihistamines at this point may help reduce the effects of a “late phase”.

Filed under Allergies, Asthma, Air Quality by Dan Buglio