Rachel Starr, 7, of Boston gets some help from her dog, Violet as she tries to build an igloo on the Boston Common on December 15, 2013. (Jessica Rinaldi For The Boston Globe)
While allergies to pet dander certainly keep many families from owning dogs, it turns out having man’s best friend as a pet might actually protect babies from developing allergies and asthma in the first place. A new study conducted with mice could explain the reason why: dust from homes with dogs has a higher amount of beneficial bacteria. This helps establish a balanced immune system in a child that’s less likely to attack harmless allergens.
Previous research suggests that the establishment of certain gut bacteria in the intestinal tracts of newborns could affect their development of asthma later in childhood. Certain harmful bacteria associated with the use of antibiotics, for example, were found by European researchers to increase a child’s risk of asthma, while living with a dog or cat in the house was found in other studies to decrease the risk.
“We wanted to see which organisms were protective,” said study co-author Susan Lynch, an associate professor of medicine at the University of California San Francisco. She and her colleagues exposed some young mice to both dust from a dog owner’s home as well as dust from a dog-free home. Then, they exposed the mice to common allergens. The researchers found that those exposed to dog dust were less likely to have allergic reactions and inflammation in their breathing passages (a sign of asthma) than those exposed to the regular dust. The results were published this week in the journal Proceedings of the National Academy of Sciences.
Researchers identified a particular bacteria in the dog dust—Lactobacillus johnsonii—and found that giving it to the mice protected them against respiratory virus infections, though not as well as the dog dust itself.
Likely, other beneficial bacteria also exist in this dust, and Lynch said future studies will try to determine what those are. “Lactobacillus could play an important role in structuring a healthy bacteria biome in the gut early in life,” Lynch said, “but we have no actual evidence of that yet.”
In other words, it’s way too early to be looking for a probiotic supplement with Lactobacillus johnsonii or other kinds of “good” bacteria to prevent allergies and asthma in kids, or to treat those who already have it.