Allergy (Allergies) Symptoms, Causes and Signs on MedicineNet.com

Font Size

Allergy/Allergies

10 Common Allergy Triggers Slideshow

Pets and Allergies Slideshow

Nasal Allergy Relief Slideshow

Medical Author: Alan Szeftel, MD, FCCP
Medical Editor: William C. Shiel Jr., MD, FACP, FACR

Introduction

In this review you will learn how allergy relates to the immune system. You will begin understanding how and why certain people become allergic. The most common allergic diseases are discussed briefly in this article.

Air Pollution and Allergies: A Connection?

Medical Author: Alan Szeftel, MD, FCCP
Medical Editor: William C. Shiel Jr., MD, FACP, FACR

Is there a link between allergies and air pollution? Does the "air we breathe" have an impact on the rising incidence of allergies and asthma? Hay fever was rare in Japan before World War II. However, pollen allergy is now common and mostly affects those living in Japanese cities and near highways. Allergic disease is also more common in highly developed countries in North America and Europe and less common in Third World countries. This suggests that there must be something about modern, urban life that promotes allergy. Let us examine the impact of air pollution.

By far the most important indoor pollutant is tobacco smoke, which is strongly associated with allergic sensitization, asthma, and other respiratory illnesses. Exposure to smoke results in the body's enhanced ability to produce IgE (the allergy antibody) that attaches to allergens (e.g. pollen, dust mites and dander). The IgE response is a key trigger of allergic reactions. Parental smoking increases the risk of their children having many respiratory illnesses, including bronchitis, chronic cough, and asthma. Smoking during pregnancy and breastfeeding results in a higher risk for the children to develop allergic eczema (atopic dermatitis).

Learn more about potential causes of allergies »

Top Searched Allergy Terms:

test, symptoms, treatment, skin rash, allergic reaction, seasonal, medications, sun, mold, red bumps, dust, cat, medicine

What does an allergy mean?

An allergy refers to an exaggerated reaction by our immune system in response to bodily contact with certain foreign substances. It is exaggerated because these foreign substances are usually seen by the body as harmless and no response occurs in non- allergic people. Allergic people's bodies recognize the foreign substance and one part of the immune system is turned on. Allergy-producing substances are called "allergens." Examples of allergens include pollens, dust mite, molds, danders, and foods. 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. Therefore, people who are prone to allergies are said to be allergic or "atopic."

Austrian pediatrician Clemens Pirquet (1874-1929) first used the term allergy. He referred to both immunity that was beneficial and to the harmful hypersensitivity as "allergy." The word allergy is derived from the Greek words "allos," meaning different or changed and "ergos," meaning work or action. Allergy roughly refers to an "altered reaction." The word allergy was first used 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."

Allergy Fact

It is estimated that 50 million North Americans are affected by allergic conditions.

The cost of allergies in the United States is more than $10 billion dollars yearly.

Allergic rhinitis (nasal allergies) affects about 35 million Americans, 6 million of whom are children.

Asthma affects 15 million Americans, 5 million of whom are children.

The number of cases of asthma has doubled over the last 20 years.