What is Allergy ?

An allergy is an abnormal reaction of the body against a foreign substance called an allergen. For most subjects, this substance does not cause trouble but in an allergic person can be responsible for various more or less serious phenomenons.

Awareness, essential first step

For developing an allergy, it is essential that the first contact between the allergen and the subject's body took place. This is called sensitization. Then, at each new encounter of the allergen and the body occurs as a consequence an allergic manifestation.

The mechanism of allergy

Normal function of the immune system

In humans, the immune system plays the role of "gatekeeper" and defends the body against external attacks. It is able to recognize antigens or markers of foreign substances to the body that lie on the surface of particles or micro-organisms. In response to the attack, the immune system produces antibodies and white blood cells capable of coming into contact with these antigens and destroy micro-organisms that carry them.

The role of immune system in allergies

In allergy, the immune system responds abnormally and exaggerated to a harmless foreign substance to the body.

In the case of allergy, the antigen is called allergen. This antigen is usually well tolerated by most of the population.However, people with allergies, the immune system will produce antibodies and white blood cells against this antigen that mistakenly considers dangerous.

A substance completely harmless for some, can cause an allergic reaction in a person said sensitized.

Allergy is a reaction inadequate, excessive and pathologic of immune system.

Allergy, a pathology increasingly frequent

Allergy is a pathology becoming more and more common. Nearly 20 % of the European population is allergic to at least one substance.

Allergy, a family origin

The risk of becoming allergic is based on family history, and we consider :

> a risk of 12.5 to 15 % if neither parent is allergic

> a risk of 25 to 40 % if one parent is allergic

> a risk of 50 to 65 % if the 2 parents are allergic

> a risk of 75 % if the 2 parents + a member of the immediate family is allergic

Allergy increasingly common in industrialized countries

Allergy is a phenomenon that affects mainly the industrialized countries.

Several explanations are suggested:

> greater diversification of food consumption with more exotic products, prepared foods with preservatives and food additives potentially allergenic.

> Air pollution also participates in sensitization to allergens (allergenic airborne particles).