There have been several studies suggesting that when exposed to a dog regularly in early infancy, children’s risk for developing allergies and asthma decreases. And now, researchers point to changes in gut microbes as the mechanism behind this safeguard.
The researchers, from the University of California-San Francisco (UCSF) and the University of Michigan, published the results of their mouse study in the journal Proceedings of the National Academy of Sciences.
They explain that when mice were exposed to dust from houses in which dogs lived, the community of microbes in their gut – known as the gastrointestinal microbiome – was “reshaped.”
This also resulted in decreased reactivity by the immune system to common allergens, they say.
In the study, the investigators introduced cockroach or protein allergens to the mice and found that inflammatory responses in the lungs – which are associated with asthma – were significantly reduced in mice that had been exposed to dust associated with dogs, compared with those who were exposed to dust from dogless homes.
In particular, the researchers singled out one species of bacteria called Lactobacillus johnsonii.
When fed to the mice, it prevented airway inflammation attributed to allergens or respiratory syncytial virus (RSV) infection – which is linked with elevated asthma risk when experienced in infancy.
Study leader Prof. Susan Lynch, from the Division of Gastroenterology at UCSF, says that the level of protection L. johnsonii offers on its own is less than that achieved from the full dust microbe catalogue from dog owners’ homes.
She says this suggests that other bacterial species are likely necessary for full protection in the airway.
Prof. Lynch says she is convinced that “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.”
Though the study showed that mice exposed to dog-associated house dust are protected against allergies and asthma, the team says their findings likely explain why children raised in houses with dogs from birth have a reduced allergy risk.
Prof. Lynch believes their findings have potential for the future, adding:
“Gut microbiome manipulation represents a promising new therapeutic strategy to protect individuals against both pulmonary infection and allergic airway disease.”
The study was funded by the National Institute of Allergy and Infectious Diseases (NIAID).
Other studies have highlighted the benefits man’s best friend bestows upon humans, including lowering risk of heart disease and providing insight into owner health.