Scientists are paying increasing attention to the “indoor microbiome,” the billions of bacteria, viruses and fungi that we share our homes and offices with. But not all those micro-organisms are bad for us, experts note. And exposure to a rich array of indoor germs may actually be salutary, helping stave off a variety of illnesses.

So there is growing concern that, in our anxiety to banish bacteria from our indoor world, we have become too clean for our own good. We run the risk of scrubbing, disinfecting, vacuuming and filtering out the fortifying mix of microscopic creatures that our immune system needs to develop properly.

Enter the dog.

Dogs roll in the mud. They sniff feces and other questionable substances. Then they track countless germs into our homes on their paws, snouts and fur.

And if the latest research on pets and human health is correct, that cloud of dog-borne microbes may be working to keep us healthy. Epidemiological studies show that children who grow up in households with dogs have a lower risk for developing autoimmune illnesses like asthma and allergies — and it may be a result of the diversity of microbes that these animals bring inside our homes.