Baby and dog
Dogs help protect babies from asthma and allergies. Dan/Flickr

Having a pet dog helps protect children from asthma and allergies as exposure to them in early infancy reshapes gut microbes to diminish immune system reactivity to common allergens.

Researchers from the University of California San Francisco and the University of Michigan have found children's risk of developing allergies and asthma is greatly reduced when exposed to a dog that lives indoors and outdoors.

Published in the Proceedings of the National Academy of Sciences, the researchers used mice to study what effect dogs have on young.

They exposed mice to cockroach or protein allergens and found that those that had previously been inside homes with dogs were much less likely to have an asthma-associated inflammatory response in their lungs.

Findings showed one specific bacterial species inside the gut of the dog-exposed mice protected them from allergens. When this bacteria was fed to mice alone, they found it could prevent airway inflammation caused by allergens.

However, they also found the level of protection was lower than that obtained by dog-exposed mice, suggesting there are other bacterial species that contribute to airway protection.

"Gut microbiome manipulation represents a promising new therapeutic strategy"

Researchers say they believe that bacteria will one day be used to reshape gut microbiome in order to prevent the development of asthma or allergies, or to treat existing cases.

Susan Lynch, who led the study, said: "The composition and function of the gut microbiome strongly influence immune reactions and present a novel avenue for development of therapeutics for both allergic asthma and a range of other diseases.

"We 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.

"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 National Institute of Allergy and Infectious Disease.

"Gut microbiome manipulation represents a promising new therapeutic strategy to protect individuals against both pulmonary infection and allergic airway disease."