Having a dog — even a dirty one — may help fend off allergies in young children
By Nathan Seppa and ScienceNews
Dogs that bring outdoor dust into the house might actually be doing a favor for babies in the home. Research suggests that exposure to doggy dust imparts immune protection to infants. A study of mice shows that the benefits derive from microbes in the dust that enter the intestines and improve the microbial mix, steering the immune system toward fighting disease and away from initiating allergic reactions.
The findings present a microbial twist in the hygiene hypothesis, which argues that a less-than-sanitary early life may prime a child’s immune system against overreacting to grass, dust mites and other ordinary substances. Past studies suggested that babies exposed to multiple siblings, day care, pets or farm living grow up to have less risk of asthma or allergy.
In the new study, researchers found that dust from a house with a dog contained more-diverse microbes than dust from a home with no pets. Since human infants ingest at least some dust, the scientists fed one kind of dust or the other to mice that were six to eight weeks old. Although unappetizing, it had the desired effect: Exposure to the dog-house dust greatly toned down reactions in the mice that were exposed to a common trigger, cockroach allergen.
Mice getting the no-dog dust had inflammation in airways. They also had evidence of excess mucus and immune proteins that are common in allergic reactions. But these reactions were virtually absent in mice that had been primed with the dog dust, the scientists reported last week in the Proceedings of the National Academy of Sciences.