Bacteria in the gut may offer clues as to why pets seems to protect kids against asthma and allergies, The Wall Street Journal reports citing a new scientific study.
Exposing mice to dust from households where dogs were allowed outdoors, the study published Monday found, significantly changed the composition of gut microbes in the mice.
When the mice were then challenged with some well-known allergy triggers, they had significantly reduced allergic responses compared with mice that had been exposed to dust from homes without dogs or that weren't exposed to any dust.
Having dogs in the house "might inoculate the GI tract" of babies and lead to a more mature immune response that is less sensitive to many allergens, said Susan Lynch, an associate professor in the division of gastroenterology at University of California, San Francisco and senior author of the study, published in the Proceedings of the National Academy of Sciences.
"We develop this great diversity of organisms [in the gut] over the first couple of years of life," Dr. Lynch said. The gastrointestinal microbiome is the subject of a growing body of research showing the bacteria play key roles in metabolism, immunity and a variety of other biological processes.
While the study looked at mice, Dr. Lynch said the findings are consistent with previous research based on human observations and are likely to apply to people.
The new study identified one specific species of bacteria, Lactobacillus johnsonii, that was strongly linked to protection against allergic responses. When isolated from the gut of one group of mice and put into the intestinal tract of other mice, "those mice were protected," Dr. Lynch said. "The immune response was significantly reduced in those animals and they looked healthier."
But they weren't as well-protected as mice with a more-diversified microbiome, suggesting other such organisms in the microbiome affect immune response.
Dr. Lynch and her colleagues, including researchers at the University of Michigan; the Henry Ford Health System, Detroit; and the Georgia Regents University, Augusta, are shifting the research to people. The aim is to develop probiotics or "microbial based therapies" that might be used to prevent or treat asthma and allergies, Dr. Lynch said.
