Get Dirty, Stay Healthy

We live in fear of the microbes that inhabit our homes and buildings. But our health may depend on preserving theirs

-  Rinku Patel

SOMEONE ONCE TOLD ME THAT A PRAYING MANTIS IN YOUR HOME BRINGS LUCK AND GOOD HEALTH. As for the one sitting on my kitchen countertop in Oakland, California, well, Jonathan Eisen certainly likes it. “That’s cool,” says the University of California at Davis microbiologist, lifting the tiny aluminum toy—with huge eyes and delicate clawlike front legs—off the cold marble. He sets it down only when something even smaller, a fruit fly, buzzes past. “Look,” he says admiringly, head cocked to my ceiling, “you have drosophilia.”

Eisen is a tall guy in his 40s with a mountain-man beard, and he has shown up at my home wearing a T-shirt with sparkly-pink block lettering that reads: “Ask me about fecal transplants.” He’s a firm believer that human health depends on bugs—not the six-legged variety, but the microbes that populate our guts and the environments in which we live, work, and play. Eisen explains that every time I open my door, a blast of air that has woven through the surrounding tree canopy carries microbes into my house—as do Amazon packages, pets, and muddy feet.

He’s musing about my oak trees when the forced-air heating clicks on. The furrows in his brow deepen. Hot, dry air shooting through a sealed house kills germs, he tells me. In fact, my whole house makes him deeply uncomfortable. It was extensively remodeled this past summer with antimicrobial fixtures, floors, and walls—now standard in many renovations. Eisen compares this practice to the overuse of antibiotics in medicine: Wipe out the natural balance of good bugs, and you might not like the organisms that survive.

A mounting body of research has shown the importance of the microbes that live inside us, and scientists have been slowly cataloguing species that live outside in