Infants who live in a house with multiple dogs may be less likely to develop allergies later in life, according to a new study.

Researchers found that infants who live in a home with two or more dogs and a high level of certain types of a bacterial substance were a third less likely to develop wheezing in the first year of life than those who didn't live with dogs.

Wheezing in infants is associated with a higher risk of developing allergies and asthma later in life.

In the study, researchers looked at the effects of pet ownership on wheezing in more than 500 infants at high risk of developing allergies because at least one parent had them.

The results, published in the Journal of Allergy and Clinical Immunology, showed that wheezing was not independently associated with either dog or cat ownership, or a high level of indoor endotoxins.

Endotoxins are natural compounds produced by bacteria. Some believe exposure to these compounds may stimulate the immune system.

However, infants living in a household with two or more dogs and a high level of indoor endotoxins (measured from house dust) were a third less likely to develop wheezing than infants living without dogs.

"Our bodies are programmed to produce allergic responses early in life," says David Bernstein, MD, professor of immunology at the University of Cincinnati, in a news release. "But there are environmental factors like bacterial endotoxins that may modify the immune system and block development of allergies early in life.

"We do not yet understand how and why exposure to high levels of bacterial endotoxins and multiple dogs in the home exert a protective effect in these high-risk infants from wheezing early in life," says Bernstein.