Medical Examiner

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.

I call up an immunologist named Mary Ruebush, author of Why Dirt is Good, a rallying cry for the Hygiene Hypothesis.

“The pendulum has swung,” she tells me. “The first few millennia of human evolution, there was no thought of cleanliness. Then when we realized there’s a link between cleanliness and disease, we went overboard.”

Like Tierno, she claims superior health. “I don’t remember having a cold or a headache, and I have absolutely no standards of hygiene whatsoever.” I suppress my instinct to say that I’m glad this is a phone interview.

 “My standard for hand-washing is this: If they look dirty or smell bad, then I wash them,” she says.

I tell her about how my son licked ice cream off the sidewalk. “Good for him,” she says. “He is going to be a healthy adult.”

When I get off the phone, I tell my wife about Ruebesh’s thesis. “That’s a wise woman,” she says.

Later that night, when she drops a cucumber slice on the floor, she bends down to pick it up and put it on Zane’s plate. “Hygiene Hypothesis!” she says gleefully. It’s her new catchphrase.


I decide to spend a week implementing Tierno’s Germ Battle Plan on myself. I promise my wife I’ll leave her and the kids out of it.

In his book The Secret Life of Germs, Tierno gives a list of antiseptic-living suggestions. On a Wednesday morning, I begin to implement them.

Wipe down the phones and remote controls weekly.

Does wiping them with moist paper towel really get the germs off? I wish I could boil my electronic equipment.

Soak all produce for five to 10 minutes in a solution of water, hydrogen peroxide, and vinegar.

“Hydrogen peroxide?” asks our babysitter, as I pour some into a bowl of apples. “Is that safe? I thought that’s what you use to dye hair.” It’s in the book, I tell her.

Wash underwear separately from other clothes to prevent a transfer of fecal residue.

Dry laundry in the sun, because the UV radiation kills germs.

A clothesline doesn’t work in New York, so I lay my shirts on the outside part of the air conditioner.

Remove showerheads and clean them with a wire brush to root out legionella, the cause of Legionnaire’s disease.

Put hypoallergenic sheets and pillowcases on your bed to keep the dust mites from snacking on your dead skin flakes, because dust mites can cause allergies.

The ones I bought are kind of slippery, but they make me feel better. Tierno himself takes his germ-proof sheets with him when he goes to a hotel. I put that on my list.

It’s been half a day, and I’m not even close to getting through my list. Though I do notice something strange. Aside from being busy, I have another feeling: righteousness.

Maybe it’s my imagination, but now I crave more order in every part of my life. I’m more annoyed when my wife is late to dinner. I’m more concerned when my son hangs around with the rambunctious elements in his class.

Does my punctiliousness have anything to do with my germ obsession? Perhaps not. But the brain is an odd place, and it’s possible that germaphobia has colored my moral view. I read a fascinating study arguing that the more obsessed you are with germs, the more politically conservative you become.

In the experiment, subjects were asked about their “moral, social, and fiscal” attitudes. “Merely standing near a hand-sanitizing dispenser led people to report more conservative political beliefs,” one of the scientists wrote. “Apparently, the slightest signal that germs might be present is enough to shift political attitudes toward the right.”

The professors speculate that that early humans often came into contact with other tribes that harbored dangerous germs. So humans evolved to have a feeling of disgust at The Other, which helped keep interactions to a minimum.

When I told one of my conservative friends this theory, he said it sounded absurd. But, he added, at least it gave him license to call liberals dirty.


From Drop Dead Healthy by A.J. Jacobs. Copyright © 2012 by A.J. Jacobs. Reprinted by permission of Simon & Schuster, Inc.