In 1967 a husband and wife team of NIAID-supported scientists discovered the IgE antibody that causes most allergic reactions.

Nonallergic people produce small amounts of this antibody, but allergy sufferers produce vast quantities as a reaction to allergens.

The IgE antibodies bind to two types of cells, basophils (circulating in blood) and mast cells, that are plentiful in the lungs, skin, tongue, and linings of the nose and intestinal tract. These cells then release histamines and other chemicals that cause allergic symptoms.

When the susceptible person encounters the same allergen again, it attaches to the IgE antibodies already bound to basophils and mast cells, starting the same chain reaction.

Anatomy of an allergic reaction

Inner-City Asthma Study
In 1997, a large NIAID-supported study documented that a combination of cockroach allergy and exposure to insects is a major cause of asthma-related illness and hospitalizations among inner-city children.

Scientists with NIAID's National Cooperative Inner-City Asthma Study looked at 476 children living in the New York City area. Most were either African American (78%) or Hispanic (16%). The researchers measured levels of cockroach, dust mite, and cat allergens in the children's homes. They also tested the children for allergies to these substances and assessed the severity of the children's asthma over the previous 12 months.

Risk factors
Their discovery: children who were both allergic to cockroaches and exposed to high levels of cockroach allergens were hospitalized for asthma 3.3 times more often than children who had only one of these two risk factors. In contrast, neither dust mite nor cat allergens was so closely associated with more severe asthma.

The study's findings will aid efforts to prevent and treat asthma in high-risk populations. That is an important public health goal--asthma-related deaths rose 118% from 1980 to 1993 among Americans younger than age 25.