Allergy

Allergies are the result of a response by the body's immune system to agents it perceives as possibly dangerous. Allergy-producing substances are called “allergens”. Allergens may be present in certain medications, in parts of plants, in house dust, in animal dander, in molds, in fungi, in foods, and in insect venom. To understand the language of allergy it is important to remember that allergens are substances that are foreign to the body and can cause an allergic reaction in certain people.

When an allergen comes in contact with the body, it causes the immune system to develop an allergic reaction in persons who are allergic to it. When you inappropriately react to allergens that are normally harmless to other people, you are having an allergic reaction and can be referred to as allergic or atopic.

The word allergy is derived from the Greek words “allos”, meaning different or changed and “ergos”, meaning work or action. Austrian pediatrician Clemens Pirquet (1874-1929) first used the term allergy in 1905 to describe the adverse reactions of children who were given repeated shots of horse serum to fight infection. The following year, the term allergy was proposed to explain this unexpected “changed reactivity”.

The aim of the immune system is to mobilize its forces at the site of invasion and destroy the enemy. One of the ways it does this is to create protective proteins called antibodies. These antibodies, or immunoglobulins (IgG, IgM, IgA, IgD), help to destroy a foreign particle by attaching to its surface, thereby making it easier for other immune cells to destroy it. The allergic person however, develops a specific type of antibody called immunoglobulin E, or IgE, in response to certain normally harmless foreign substances. To summarize, immunoglobulins are a group of protein molecules that act as antibodies. There are 5 different types: IgA, IgM, IgG, IgD, and IgE. IgE is the allergy antibody.

Most people are susceptible to skin allergies or reactions at some time during their lives. The most common such sensitivity is to plants such as poison ivy or poison oak. In susceptible individuals, contact with one of these plants produces an itchy, blistering rash. Another type of allergy causes swelling of tissues beneath the skin or in the throat for no apparent reason. All of these discomforts are caused by histamines and other chemicals released into the skin or under the lining of the throat or bronchial passages as a result of allergic response. The common skin allergies are dermatitis, hives, and angioedema.

Allergies of the respiratory tract often produce symptoms that are similar to those of a cold: headache, stuffy or runny nose, cough, and sneezes. All respiratory allergies represent responses of the immune system to airborne allergens. The most common respiratory allergies are hay fever, allergies to mold, dander and dust, and asthma.

Allergies to foods, drugs, and insect stings may be the result of antibody responses to allergens that have come into contact with the internal systems of the body. The symptoms may range from a simple rash to a systemic reaction involving the gastrointestinal tract and the respiratory and cardiovascular systems.

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