Dec 21 (HealthCentersOnline) - Infants living in homes with multiple dogs are less likely to develop wheezing in the first year of life, according to a new study.

A common breathing problem, wheezing is a whistling or high-pitched sound that occurs when breathing tubes are constricted (narrowed) or obstructed. Wheezing in infants is associated with a higher risk of developing allergic diseases later in life.

Past research suggests that either pet ownership or exposure to high levels of bacterial contaminants called endotoxins can protect against an increased risk for future allergic diseases. However, researchers at the University of Cincinnati (UC) found that a combination of these factors may be beneficial. They found that infants living in homes with high levels of endotoxins and multiple dogs are more than two times less likely to wheeze than other infants.

During the study, the team evaluated the effects of cat and dog ownership and endotoxin exposure on 520 infants. Enrolled in the Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS), each participant was determined to be at greater risk for developing allergies because at least one of their parents had known allergies. The researchers measured endotoxin levels in dust samples collected from each infant's home. They also noted the number of siblings and collected information about the home, including the presence of mold or secondhand smoke. The infants were also monitored for the development of environmental and food allergies with annual skin prick tests.

After reviewing the results, the team found that wheezing was not associated independently with either dog or cat ownership or high levels of indoor endotoxins. However, high endotoxin exposure in homes with multiple dogs was associated with less wheezing in the infants.

"Our research presents evidence that pet ownership offers a protective effect against development of lower respiratory symptoms in young children," adds Dr. David Bernstein, professor of immunology and senior author for the study, in a press release.

"Exposure to high endotoxin levels in the home may not be an important determinant of aeroallergen sensitization during infancy," stated Bernstein. "We do not yet understand how and why exposure to high levels of bacterial endotoxin and multiple dogs in the home exert a protective effect in these high-risk infants from wheezing early in life."

Endotoxins are compounds secreted from bacteria and other disease-causing agents. They are believed to stimulate the immune system in a variety of ways.

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

Although the results of the study are promising, more research is needed to determine if these early protective effects have long-term benefits.

Details of the study were provided by the University of Cincinnati in a press release. The full study appears in the December issue of the Journal of Allergy and Clinical Immunology.

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