A.J. Jacobs’ Drop Dead Healthy chapter: Germs, germaphobes, and the hygiene hypothesis.

The Germs That Don’t Kill You Will Make You Stronger

The Germs That Don’t Kill You Will Make You Stronger

Health and medicine explained.
April 18 2012 8:15 AM

Germ Porn, Hand-Washing, and the Hygiene Hypothesis

An excerpt from A.J. Jacobs’ new book, Drop Dead Healthy.

For two years, A.J. Jacobs went on a quest to be as healthy as humanly possible. That meant revamping every part of his physical life, including diet, exercise—and his relationship with microbes. This article is excerpted from his new book, Drop Dead Healthy: One Man's Humble Quest for Bodily Perfection, out now.

Hand washing.
Someone washing their hands.

Photograph by Medioimages/Photodisc/ThinkStock.

I’ve long been a fan of germ porn. Perhaps you’re familiar with the genre. I’m talking about those news segments that warn you that there are more germs on your remote control than on your toilet seat. Your sponge is a hot zone, and your cell phones should be quarantined!

The news will cut to footage of unwashed hands under black light, all Jackson Pollocked with glowing purple germ splotches.


Germ porn probably isn’t good for me, but it’s a perverse masochistic pleasure. It feeds into my germaphobia, a condition I’ve been struggling with for years, long before it became a familiar trope on TV detective shows.

My wife hates when I watch germ reports. She’s on the opposite end of the spectrum. Our society is too hygiene-obsessed, she says, and it’s turning us into immunological pansies. Go ahead, she’ll tell the boys, play in the sandbox, despite what daddy says about residual fecal matter. Drink from that water fountain. A few months ago, our son was eating an ice cream cone from the overpriced ice cream store in our neighborhood. Then his scoop fell on the sidewalk. Amazingly, he didn’t get upset. Instead, he got down on all fours and started licking it off the pavement like a golden retriever. A woman walking behind him gasped, “Oh, my God.” But my wife? She had no problem with it. New York is one big dinner plate.

Which is why she’s even less happy about the visit I’m about to make. I am meeting with the Ron Jeremy of microbial fetish videos: Dr. Philip Tierno, the director of Clinical Microbiology and Immunology at New York University Langone Medical Center. Also known as Dr. Germ. You might recognize Tierno from his segment about pillows on The Today Show. It featured millions of skin-eating dust mites and has made me lose at least a week of sleep. He’s the expert of experts.

“He’s an enabler,” Julie says. She might have a point.

But for the last year, I’ve been working on a project to maximize my health in all areas. I need to figure out the best way to conquer these germs.


I arrive at Tierno’s midtown lab, where I find him studying a slide of bacteria. He’s bald, with a neat white beard and round-wire-rim glasses. He sticks out his hand to greet me.

What? Dr. Germ wants to shake hands? That makes no sense at all. I respond by offering him my elbow for an elbow bump.

“Ah, this guy knows what he’s doing,” says Dr. Tierno. I beam. We go back to his cluttered office, filled with a microscope, slides, biology books, and 11 bottles of cleaning fluids. Bach plays in the background.

First, Tierno wants me to know that germs suffer from some bad PR. Most bacteria are harmless. In fact, human beings are mostly germs. We are walking around with 90 percent germ cells, 10 percent human cells. They’re in our gut, in our mouth, in our eyebrows.

“There are 156,000 categories of germs around, but only a small percentage are pathogenic. Maybe 2,000 of these.”

Ah, but those 2,000 – you don’t want them anywhere near you. Consider that infectious disease is the second leading cause of death in the world. Here’s a disturbing statistic: Every year, 100,000 people in the world die because of infections they got at the hospital. Another one: Every year, germs in food sicken an astounding 76 million in the United States, according to the Centers for Disease Control and Prevention.

Dr. Tierno thinks America needs a massive public education campaign on hand-washing, along the lines of our anti-smoking PR blitz. “It’s the single most important thing you can do for your health,” he says. He may have a point.

The key is to do it well, which few of us do. Most of us are hardly better than the French aristocrats in the court of Louis XIV. Back then, says Tierno, doctors advised washing only the tips of the fingers, for fear that water transmitted disease.

Tierno—who says he hasn’t had a cold in four years—walks me down the hall to the bathroom for a hand-washing demo. He splashes water on his hands, squirts the liquid soap onto his hands and lathers up for 30 seconds before returning his hands under the water.

 “Around the wrists. In between the fingers. Getting each nail.”

He squishes and slides his hands together. He digs under his nails with his thumb and flicks his wrist. It’s a virtuoso performance, like Yo-Yo Ma playing the cello or Al Pacino screaming obscenities. It’s a long way from the average person’s five-second dunk.

 “Happy Birthday Philly Boy,” he sings as he finishes up. “Happy birthday to you.” (For those who don’t know, you’re supposed to sing the entire birthday song during washing, to make sure you take your time.)

When we get back to his office, I grill him on the questions he gets from every John Q. Germaphobe:

Do Purell and other hand sanitizers work?

Yes. “You need to make sure you use enough. A quarter sized dollop.” Teirno, along with the CDC, recommends alcohol-based gels if you can’t wash your hands. 

Do Purell and anti-bacterial soap create supergerms? Like MRSA?

“No. Germs don’t develop a resistance to alcohol or antibiotic soaps. They can develop a resistance to antibiotics.” Tierno recommends against popping antibiotics every time you get a cold. But at least in Tierno’s view, Purell and antibacterial soaps don’t cause supergerms.

Should I use antibacterial soap?
“Ordinarily, you don’t need anti-bacterial soap. You can get along with regular soap and warm water.” The exception is when you’re cooking foods, especially meat.

I walk out feeling both exhilarated and stressed out. My wife was right. He is an enabler.


In the interest of equal time, I decide to look into those on my wife’s side of the germ fence. Many scientists agree with her. They’ve named their theory the Hygiene Hypothesis. The idea is that children in modern First World countries aren’t exposed to enough germs, a situation that throws off the development of the immune system. Our immune cells don’t get the chance to learn to recognize and assassinate the bad guys. Our overly sanitized world could be responsible for the dramatic rise in allergies and asthma.