Allergies are caused by specific substances that, in some people, can cause their immune system to act in an extreme way. As soon as the body of an allergic person makes contact with the respective substance, the immune system is alerted and causes a specific reaction. Generally, these substances (”allergens”) have no particular effect in other people. Allergies can be caused by any number of sources: plants, food, animal hair.
People that have an extreme reaction to a certain substance that usually causes no harm to others are refered to as allergic. In 1905 infections in children were treated with horse serum injections, that caused an opposite reaction to the one intended, thus this kind of reaction was named „allergy” from then on. The term “allergy” has a Greek ethimology and it was used for the first time by Clemens Pirquet, a pediatrician, when he tried to describe good immunity and a hightened sensitivity as well.
How do allergies develop?
First, let’s imagine the following situation: a family with two children gets a dog as a pet. After a while (months, weeks) the mother begins to sneeze and manifest itchiness of the eyes. One of the children coughs and has difficulty breathing, especially when he is closest to the animal. The other two members of the family have no such reactions.
The immune system guards the organism against infections, and it is alerted by external substances or antigens. The presence of antigens in the body cause the production of antibodies, but do not necessarily cause an allergic reaction. The substances that launch allergies are certain antigens that also lead to the production of Immunoglobulin E (antibodies that are triggered by allergens). Antibodies are special proteins that fight infections and focus on specific substances. The Immunoglobulins (IgG, IgM, IgA, IgD) attack a foreign particle (for example, dog or cat dander) and make it easier for other types of antibodies to destroy it.
All people have lgE in their systems. People who develop allergies have it in larger quantities and if they are exposed to allergens once, it is very likely that an allergic reaction will take place again, since the immune system is more sensitive. During this reaction, certain chemicals are released, like histamine. This chemical causes inflammation and other typical symptoms.
Normally, dog dander, for example, produces different kinds of antibodies, that do not cause allergic reactions. In the previous example, the other two members of the same family did not present any allergic symptoms, because the foreign dander particles were eliminated by the immune system, irrespective of the dog itself.
Allergy risk and cause
Chidren are more prone to allergies, but they can appear at any age. Some allergies can manifest symptoms even during the adult life for the first time. Some allergy-related symptoms and effects – like asthma – can affect people also during the adult life, while others, like allergic rhinitis symptoms decline with age.
The risk of developing an allergy can be estimated by analizing the family history in allergies, as it seems that the predisposition to allergies is hereditary. Still, the exact triggers of developing the symptoms at all are unknown, even though a tendency towards allergies is known.
The environment plays a big role in causing allergies. Therefore, smoking, infections, certain pollutants and endocrine levels are significant factors.