Allergies

Illustration by S. Edelstein, Courtesy: NIEHS The word allergy, coined in 1906 by the Austrian pediatrician Clemens von Pirquet, comes from the Greek word allos, meaning "change in the original state." Allergy describes the altered or heightened response your immune system may display toward a substance. Only IgE-mediated immune responses are generally considered to be true allergies, although increasingly a better understanding of the complexity of the immune system suggests that several different pathways may result in allergic symptoms.

In an IgE-mediated allergic response, a protein such as pollen stimulates the production of IgE antibodies--specific to that protein--in the blood. The next time the body encounters the protein (called an allergen), the antibodies cause an overreaction to the substance, stimulating a series of chemical mediators that produce allergic symptoms. An estimated 40 million people in the U.S. suffer from allergies.

Common respiratory allergens in the Houston area include dust mites, Illustration by S. Edelstein, Courtesy: NIEHS pollen (click here for Houston's pollen count today), animal dander and mold. Allergic symptoms often include:

itching;
sneezing;
runny nose;
sinusitis; and
irritated eyes.

Some people are severely allergic to particular substances and can experience a life-threatening response known as anaphylactic shock. Fire ant and wasp stings, some medications (such as penicillin) and some foods (such as shellfish and strawberries) are more likely to produce these serious reactions in hypersensitive individuals.

Allergic disease has increased significantly in developed countries over the last few decades, especially in urban areas. There is considerable evidence that man-made pollution, especially pollution from cars and trucks, is responsible for at least part of this increase (O'Connell, 2003; Shima, 2002). Most man-made pollutants, such as diesel exhaust and gasoline fumes, are not proteins and therefore do not produce the classic IgE-mediated allergy. Nevertheless they may stimulate other pathways that lead to similar symptoms or perhaps destabilize the immune system so that a person is more likely to experience IGE-mediated allergies.