When I was writing my book on the microbiome, Tending Your Internal Garden (free ebook until 7/13/17), I was amazed that we tend to share more of our bacteria with our dogs than our children. It makes sense, since dogs tend to lick us more than our children (at least after the age of three). But a recent study reported by the New York Times now tells us that all that dog licking is good for us.
According to the NYT, dog licking and the bacteria they bring with them raised the number of 56 different bacterial species found in our homes. Dogs outperformed cats, who only brought in 24 different species.
Now, keep in mind that the average home has 125,000 bacterial species and 70,000 species of fungi. We’re giving off roughly 38 million bacteria ourselves every hour. So a few more species shouldn’t make that much difference.
But, as I point out in Tending Your Internal Garden, diversity is the key. More species compete with each other. They keep each other in check, much like a perpetual round of antibiotics. What you don’t want is one dominant species, either in your home or in your body. One species left unchecked will change into a tyrant, rapidly reproducing itself and impacting your immune system.
The real enemy is sterility, or the myth of sterility. Washed hands, operating rooms, even NASA space probes are not sterile. They are MOSTLY sterile. Which means that they harbor a few resistant bacteria who will take over that vast stretch of empty space if given the chance. (A concerned mother has asked me to add: You should still wash your hands, because it will decrease the number of bacteria right before you eat. But if you have washed your hands hours ago, your hands are no longer clean.)
Even if the bacteria don’t get you, your immune system might. We’re set up to be dirty, absolutely filthy. Your immune system, bless its little heart, is a bit like a biker gang running security at a heavy metal concert. Give it a few rowdies, and it’s happy. But if it’s a hippie love-in with no rowdies, the immune system is going to start wanting to crack some heads just for the heck of it. We experience these overreactions as allergies, since the immune system has gone after dust mite turds or flower pollen as a possible threat to our existence.
Enter our faithful hound, dragging eu de skunk, every flower pollen in the yard, and more than dust mite turds into our homes. All these little nuisances are just what we and our offspring need to lower our allergic responses. After 40,000 years, dogs are finally getting their due as man’s best friend.