Man’s best friend may be his best bet to evade asthma and allergies. That is the conclusion of a new study from Tufts University School of Medicine, where researchers have determined that a pet dog allowed indoors can reduce a young child’s risk of developing certain respiratory complications. The findings hint at new public health recommendations for at-risk individuals.

Researchers have long been aware of statistical correlations between dog ownership and a reduced allergy risk. However, few research papers have attempted explain why this protective effect is obtained. The current study, which is published in the journal Proceedings of the National Academy of Sciences, submits one of the first explanations to dogs’ anti-allergenic properties.

According to lead researcher Susan Lynch, the team “set out to investigate whether being exposed to a distinct house dust microbiome associated with indoor/outdoor dogs mediated a protective effect through manipulation of the gut microbiome, and by extension, the host immune response." In other words, Lynch and her colleagues wanted to know whether sharing an environment with a dog diminishes your disposition to allergies and respiratory complications by reshaping your gut bacteria.  

To investigate, the team designed an experiment with mice. Half of the subjects were exposed to dust from homes with dogs, and the rest were not. All subjects were then exposed to protein and cockroach allergens.

The researchers found that compared to the control group, the dust-exposed mice had much lower asthma-associated inflammatory responses in the lungs. These protected subjects also exhibited a reshaped microbiome brimming with “good” bacteria. One particular microbe species stood out: Lactobacillus johnsonii. When this was isolated and fed directly to other mice, a comparable protective effect was obtained.

The current study exemplifies the exciting emergence of new therapeutic and diagnostic solutions involving dogs. Another project can be found at the Working Dog Center of the University of Pennsylvania’s School of Veterinary Medicine, where dogs McBaine, Ohlin, and Tsunami are currently undergoing highly specialized detection training that will allow them to sniff out ovarian cancer.  

The team is confident that the new findings will contribute to the continued search for anti-allergenic agents and treatment options. Although the results are so far limited to mice, human trials are already underway. "The results of our study indicate that this is likely to be one mechanism through which the environment influences immune responses in early life, and it is something we are currently examining using human samples in a large multi-institutional collaborative study funded by the NIAID," Lynch said in a press release. "Gut microbiome manipulation represents a promising new therapeutic strategy to protect individuals against both pulmonary infection and allergic airway disease."

Source: Fujimura KE, Demoor T, Rauch M, Lukacs NW, et al. “House dust exposure mediates gut microbiome Lactobacillus enrichment and airway immune defense against allergens and virus infection.” [published online ahead of print December 16, 2013].PNAS.doi:10.1073/pnas.1310750111.