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December 2006 Issue

UC researchers have found that children who live in homes with high endotoxin levels and multiple dogs are much less likely to wheeze than other infants. Pictured here is Callie Gibson.
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Man's Best Friend Might Help Decrease the Development of Infant Allergies

By Amanda Harper
Published December 2006

Living in a home with multiple dogs may help reduce an infant’s risk for developing allergies later in life, according to a new UC study.

Led by David Bernstein, MD, UC researchers have found that infants living in homes with high levels of endotoxins (contaminants) and multiple dogs were more than two times less likely to wheeze than other infants. Researchers found that wheezing was not associated independently with either dog or cat ownership or high levels of indoor endotoxins; however, high endotoxin exposures in homes that also had multiple dogs resulted in less wheezing.

“Our research presents evidence that pet ownership offers a protective effect against development of lower respiratory symptoms in young children,” says Bernstein.

The findings conflict with earlier studies suggesting that exposure to either high endotoxin levels or pet ownership can reduce the risks of future allergic diseases, the UC team reports in the December 2006 edition of the Journal of Allergy and Clinical Immunology

“Exposure to high endotoxin levels in the home may not be an important determinant of aeroallergen sensitization during infancy,” explains Bernstein, professor of immunology at UC and senior author of the study. “We don’t yet understand how exposure to high levels of bacterial endotoxin and multiple dogs in the home protect these high-risk infants from wheezing early in life.” 

Endotoxins are natural compounds secreted from pathogens,  like bacteria, that are commonly found in the intestines and feces. Scientists believe that endotoxins can stimulate our immune systems in many different ways.

“Our bodies are programmed to produce allergic responses early in life,” Bernstein says, “but there are environmental factors, like bacterial endotoxins, that may modify the immune system and block development of allergies early in life.”

The team analyzed the effects of pet ownership (cats and dogs) and endotoxin exposure in 520 infants enrolled in the Cincinnati Childhood Allergy and Air Poll-ution Study who were identified as being at greater risk for developing allergies because at least one parent had known allergies. The five-year study examines the effects of environmental particulates on childhood respiratory health and allergy development.

Researchers collected dust samples from the infants’ homes to measure endotoxin levels. They also determined the number of siblings and gathered information about the home, including the presence  of mold and second-hand smoke. Environmental and food allergy development was monitored through annual skin prick tests.

Previous studies have addressed the role of pet ownership in childhood allergy development; however, findings have been inconsistent, according to Bernstein. Until now, it was unclear whether animal ownership, endotoxin exposure or a combination of the two resulted in wheezing. Bernstein says further research is needed to determine if these early protective effects have long-term benefits.

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