Can hand sanitizers like Purell really stop people from getting the flu?

How to fix health policy.
Feb. 24 2010 2:00 PM

How To Sell Germ Warfare

Can hand sanitizers like Purell really stop people from getting the flu?

Illustration by Mark Alan Stamaty. Click image to expand.

Our homes and workplaces, we're told, are trying to kill us. Recently, a University of Arizona microbiologist named Charles Gerba, author of hundreds of scientific papers about household microbes, gave a terrifying lecture at the offices of the Food and Drug Administration. Gerba—who, incidentally, has a child with the middle name Escherichia—that's what the "E" in E. coli stands for—explained that a kitchen sponge and sink are home to thousands of times more bacteria than a toilet seat. Plus, 10 percent of household dishrags contain salmonella. After playing with other children, toddlers have more fecal bacteria on their hands than does a person exiting a public toilet stall. Those toilets, by the way, aerosolize so many droplets with each flush that Gerba compares their dispersion to "the Fourth of July." And every public swimming pool he's ever tested has contained disease-causing viruses.

In response to these kinds of data, more than 700 products promise to help consumers kill bacteria, molds, and viruses in their homes and workplaces, from ultraviolet lights meant to kill toothbrush bacteria, to dishwashers that superheat silverware, to specially treated doormats. Three-quarters of all Americans use six or more antimicrobial products each day.

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Even before the H1N1 outbreak, alcohol-based sanitizers like Purell enjoyed 53 percent annual sales growth, and Americans spent $117 million per year on them. With the advent of the H1N1 influenza pandemic last year, national germ-phobia kicked into even higher gear. The Centers for Disease Control's flu information Web site recommends regularly disinfecting kitchen counters, bedroom furniture, toys, and any other "surfaces." (In marketing terms, consumers were asked to increase their daily number of "wiping events.") Public-health authorities advised exhaustive, frequent hand-washing with hand sanitizers to fight flu. Soap and sanitizer manufacturers targeted massive ad campaigns to encourage more frequent hand-washing. Such products, their makers promise, can help families stay safe from the filth around them. Purell's slogan wistfully calls upon us germ-phobes, presumably paralyzed by fear, to "imagine a touchable world."

Yet the data tell a less compelling story about sanitizers like Purell. In 2005, Boston-based doctors published the very first clinical trial of alcohol-based hand sanitizers in homes and enrolled about 300 families with young children in day care. For five months, half the families got free hand sanitizer and a "vigorous hand-hygiene" curriculum. But the spread of respiratory infections in homes didn't budge, a result that "somewhat surprised" the researchers. A Columbia University study also found no reduction in common infections among inner-city families given free antibacterial hand soap, detergent, and cleaning supplies. The same year, University of Michigan epidemiologist Allison Aiello summarized data on hand hygiene for the FDA and pointed out that three out of four studies showed that alcohol-based hand sanitizers didn't prevent respiratory infections. Then, in 2008, the Boston group repeated the study—this time in elementary schools—and threw in free Clorox disinfecting wipes for classrooms. Again, the rate of respiratory infections remained unchanged, though the rate of gastrointestinal infections, which are less common than respiratory infections, did fall slightly. Finally, last October, a report ordered by the Public Health Agency of Canada concluded that there is no good evidence that vigorous hand hygiene practices prevent flu transmission.

Why, then, do so many people think widespread use of hand sanitizers like Purell are the cornerstone of flu prevention? To be sure, hand-washing can save lives in medical settings. In 1847, Hungarian doctor Ignaz Semmelweis discovered that washing one's hands with chlorine between deliveries practically eliminated fatal infections among laboring women. (His colleagues ignored him and later committed him to a mental hospital, where he was beaten to death by guards.) Today, numerous modern studies show that in randomized trials, meticulous hand-washing, when coupled with other infection control measures like surgical draping and universal gloving, reduce the rate of life-threatening infections during surgery and intensive care unit stays.

But in hospitals, outside of these clinical trials, just half of doctors and nurses regularly clean their hands before patient care, despite widespread publicity. More worrisome: In hospitals where massive educational efforts have increased hand-washing rates from 40 percent up to 70 percent, there has been no overall reduction in infection rates. Even in highly regulated places like hospitals, the promising benefits of hand-washing remain largely unrealized.

Now, that doesn't mean we should give up on hospitals. But we need to be realistic about what Purell can do to fight flu in the home and in public. To begin, the influenza virus mostly spreads via tiny droplets in the air (for example, from sneezes)—not by dirty hands or surfaces—which limits the role of Purell. It probably wouldn't matter even if flu transferred though hand contact, which is how most cold viruses spread. Though Purell kills them in the lab, hand sanitizers don't stop their spread in the real world. The average child touches his or her mouth and nose every three minutes, and both adults and children come in contact with as many as 30 different objects every minute. Even hospitals can't get staff to use Purell before seeing patients; it's impossible for day care staff, parents, or teachers to wash a child's hands 20 times each hour.

Purveyors of antimicrobial products are happy to indulge our worries about germs surrounding us. During the H1N1 pandemic, public-health agencies encouraged their marketing pitches despite evidence the products do little to help. It's likely that hand-sanitizer users falsely believed they were protected from flu and thus deferred vaccination, which is by far the more effective way to prevent its spread. According to the Centers for Disease Control, only one in five Americans was vaccinated by early 2010—and just one in four health care workers and high-risk patients got the shot.

So you can believe all the germ hype and end up like the obsessive-compulsive billionaire Howard Hughes. Or you can follow the data and get a flu shot, wash your hands sensibly after using the bathroom and around meals, and stop wasting money on hand sanitizers.

Unless, of course, you work in a hospital.

Darshak Sanghavi, a pediatric cardiologist, is a fellow of the Brookings Institution and Slate’s health care columnist. Follow him on Twitter.