National Jewish expert says bacteria by-product found in household dust may protect infants from asthma later in life

May 10, 2000

Cleanliness may be next to godliness, but National Jewish Medical and Research Center researchers say that a little dust and dirt in the home may help prevent asthma later in life.

Environmental endotoxin may have an allergy-protective effect in some infants whose homes have high levels of the bacteria by-product. "Endotoxin seems to drive the immune system to produce cytokines that inhibit certain processes in the body that may lead to asthma," said Andy Liu, M.D., a National Jewish childhood asthma specialist and principal author of the article today's issue of The Lancet.

Children not sensitized to common inhaled and food allergens had significantly higher endotoxin levels in their homes --more than twice as high -- as children who were sensitive to the same allergens. Allergens can trigger an asthma attack for many of 17 million children and adults in the United States with the lung disease.

"Exposure to endotoxin may play a role in the prevention of allergen sensitization during infancy," he said. However, if a child or adult already has asthma or allergies, the presence of endotoxin in the home can exacerbate the disease.

National Jewish researchers studied the homes of 61 infants, 9-24 months old, with at least three documented episodes of wheezing, which can be an early indicator of asthma. The infants were tested for sensitivity to dust mite, cat, dog, cockroach, mouse, milk, egg and soy. Of the 61 asthma-prone infants, 51 tested negative to these inhaled and food allergens. In the homes of children with negative allergen skin tests, the concentration of endotoxin was the highest.

"Children who are allergen-sensitive have less environmental endotoxin in their homes," Dr. Liu said. "The amount of environmental endotoxin seems to correlate with immune system development."

Endotoxin levels were determined by checking house dust collected from the living room, kitchen and bedroom floors, a couch and the child's bed. Endotoxin is part of the cell wall of common bacteria. When bacteria die, the cell wall collapses and endotoxin is released into the environment, finding its way into the air and dust. Bacteria that produce endotoxin are found in soil, and the feces of human and animals, including household pets.

Because asthma rates are very low in many agriculture-based countries and farming communities -- compared to metropolitan areas -- researchers believe that early exposure to environmental endotoxin may provide protection against developing asthma later in life.

"These findings suggest that one common thread in these communities, where allergies and asthma are uncommon, may be early childhood exposure to environmental endotoxin. This may be an important clue in the development of effective and safe asthma prevention," Dr. Liu said.
For more information about asthma and endotoxin, call LUNG LINE, 800-222-LUNG, or e-mail,

The number 1 respiratory hospital in the U.S. for two consecutive years, U.S. News & World Report, 1998-2000.

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