Hand Sanitizers Won’t Save You

Good in a pinch, they don’t beat soap and water and likely may not live up to marketing claims

A photo of a person squirting hand sanitizer out of a bottle onto their hands.

JJohn Newsam rarely uses hand sanitizers. “Perhaps once every month or two,” he says. “And pretty much only when using a portaloo, when soap and water are not available.” Newsam is CEO of Tioga Research, which studies new formulas for everything from skin care products to topical drugs. With a PhD in chemistry from Oxford University, he knows that a good scrubbing with soap and water is the preferred method for ridding his hands of a wide range of infectious germs.

In a pinch, hand sanitizers are deemed useful by the U.S. Centers for Disease Control and Prevention (CDC), but the common marketing claims of “99.99% effectiveness” are based on laboratory tests involving certain germs, not entirely real-world efforts by sometimes imperfect and rushed humans slathering on some goop in a haphazard battle against the gamut of potentially debilitating and even deadly microbes out there.

“If soap and water are not available, using a hand sanitizer with at least 60% alcohol can help you avoid getting sick and spreading germs to others,” according to the CDC. This can be useful in subways or other public places where regular hand-washing isn’t possible. The agency says hand sanitizers “work well” in hospitals, where health care workers’ hands are generally free of grease and dirt. But when hands are dirty or greasy, “such as after people handle food, play sports, work in the garden, or go camping or fishing,” the agency says, “hand sanitizers may not work well.”

Newsam thinks hand sanitizers might in fact offer a false sense of security.

“If the sanitizer is not applied properly, there may well be areas of skin surface from which the microbes are not removed,” he says. And as with regular hand-washing, it’s important to remember that any benefits do not linger. “As soon as the alcohol has evaporated and the hand comes in contact with another surface populated by microbes, there is the risk of immediate recolonization.”

The CDC says soap and water should always be the go-to solution before eating or preparing food, after using a bathroom or visiting someone who is sick, after coughing, sneezing, or blowing your nose, or whenever your hands are visibly dirty.

How hand sanitizers work

The active ingredient in hand sanitizers — in most products it’s ethyl alcohol, also called ethanol, the stuff of booze — works by “dissolving the outer coating of bacteria and viruses and basically exploding them,” according to the American Chemical Society (ACS). That’s distinctly different from soap and water, which with a proper 20-second scrub loosens grease, grime, and germs from the skin and washes it all away, rather than killing the microbes.

“Those numbers are usually the result of lab testing, but real life is messier.”

Meanwhile, marketing claims on hand sanitizers are bold-sounding but come with significant, mostly unmentioned, caveats. An alcohol-based product called Purell Advanced Hand Sanitizer claims it “kills 99.99% of most illness-causing germs.” Another product, Dial Complete, with the active ingredient benzalkonium chloride, claims instead to kill 99.99% of bacteria, with no mention of whether it works on the flu, coronaviruses, or other germs.

“Those numbers are usually the result of lab testing, but real life is messier,” the ACS points out.

“Alcohol-based hand sanitizers can quickly reduce the number of microbes on hands in some situations, but sanitizers do not eliminate all types of germs,” the CDC says. Some germs, in particular, are less affected by sanitizers, including diarrhea-inducing noroviruses and the parasite Cryptosporidium (aka Crypto).

Meanwhile, science has not established the likelihood of infection when a given batch of microbes is reduced in number but not eliminated. We simply don’t know the risk of that 00.01%, or whatever percentage might be left behind by less-than-perfect application and use of hand sanitizers.

Regular soap, if used properly, has the added benefit of helping rid hands of potentially harmful chemicals, something alcohol-based hand sanitizers don’t do. One study found farm workers who use hand sanitizers have higher levels of pesticides in their bodies.

The FDA slaps a hand

The Food and Drug Administration (FDA) is currently reviewing the safety and effectiveness of ethyl alcohol, isopropyl (rubbing alcohol) and benzalkonium chloride — the three active ingredients in 97% of all hand sanitizers, which the agency calls “consumer antiseptic rubs.” A previous review resulted in a ban on 28 other active ingredients that had been used in hand sanitizers, and the FDA requested more test data from manufacturers on the three that remain. The agency says it does not expect any significant changes based on its final ruling.

Meanwhile, the FDA recently cracked down on one company’s marketing claims it says are not supported. In January, the agency warned Gojo Industries to stop claiming its Purell Healthcare Advanced Hand Sanitizers, which are marketed both to the health care industry and to consumers, are capable of preventing the flu, norovirus, Ebola, and the drug-resistant superbug MRSA. “FDA is currently not aware of any adequate and well-controlled studies demonstrating that killing or decreasing the number of bacteria or viruses on the skin by a certain magnitude produces a corresponding clinical reduction in infection or disease caused by such bacteria or virus,” the agency wrote in a letter to Gojo.

The FDA did not specifically refute the “99.99%” claims, and it did not suggest any Purell products be recalled.

“Gojo took immediate action to respond to FDA,” Gojo spokesperson Samantha Williams tells Elemental. “Our actions included editing some of our marketing on our website and social media. It is important to emphasize that the FDA letter was not related to the safety or quality of our products, or our manufacturing processes,” Williams said. “Our products can and should continue to be used as part of good hand hygiene practice, to reduce germs.”

The case remains open as of this writing, according to FDA spokesperson Jeremy Kahn, who said the agency otherwise doesn’t comment on ongoing cases.

Lab testing vs. actual use

Marketing claims for the effectiveness of hand sanitizers are based on lab tests, sometimes done by the manufacturers themselves, and other times by independent laboratories based on FDA protocols, according to a person in charge of testing sanitizers and disinfectants at one such independent lab. The results are kept private.

The initial tests involve high concentrations of isolated germs and short amounts of time in contact with the sanitizer, to “mimic a worst-case scenario,” explains the source, who asked not to be identified, given the private nature of the relationship with manufacturers. “Laboratories like ours only test for the effectiveness against microorganisms; we do not use human subjects in our testing,” the source says.

Testing then continues at other labs, also typically contracted by the manufacturer, to test in clinical settings under strict FDA protocols. “During clinical laboratory testing, they select a variety of human subjects to test the product in a real-life situation,” the source explains. “For hand sanitizers, they are testing different hand sizes, how individuals apply the hand sanitizer, and the amount of sanitizer that is used.”

The researchers took actual mucus from an infected person, put it on people’s fingers, and exposed it to hand sanitizer. The virus remained active for two minutes.

Far less often, tests are done by outside researchers who make the results publicly available. One such recent lab test shows results can indeed be different when the experimental settings more closely resemble product use in real conditions. The test, done by independent university researchers, revealed that the influenza A virus (IAV) can find protection from alcohol-based hand sanitizers inside mucus, the gooey stuff of snot that can float clear across a room when people sneeze. The researchers took actual mucus from an infected person, put it on people’s fingers, and exposed it to hand sanitizer. The virus remained active for two minutes.

“The physical properties of mucus protect the virus from inactivation,” says study leader Dr. Ryohei Hirose, a physician and molecular gastroenterologist at Japan’s Kyoto Prefectural University of Medicine. “Until the mucus has completely dried, infectious IAV can remain on the hands and fingers, even after appropriate antiseptic hand rubbing.”

Hirose and colleagues say the experiment exposes a possible flaw in lab tests, which are typically done with dried mucus, they say. In fact, when they repeated the experiment with dry mucus, the virus was deactivated much faster, within 30 seconds.

Regular soap and water, with scrubbing, lifts the germ-laden mucus from the skin and washes it away.

In the journal mSphere, the researchers acknowledge that even their experiment doesn’t fully account for real-world use, where hand-rubbing may speed up the killing action of a sanitizer.

On the other hand, people might rush the process or fail to follow product directions, which differ based on the active ingredient. “Although alcohol-based hand sanitizers can inactivate many types of microbes very effectively when used correctly, people may not use a large enough volume of the sanitizers or may wipe it off before it has dried,” the CDC says.

The alcohol-based Purell product mentioned above directs consumers to “put enough product in your palm to cover hands and rub hands together briskly until dry.” (In this reporter’s test, the recommended single squirt fully covered both hands, and it took about 20 seconds to rub until dry.)

Meanwhile, the bacteria-killing Dial product using a foam made of benzalkonium chloride, which is alcohol-free but also kills bacteria by destroying their outer membrane, says to “lather vigorously for at least 15 seconds” then “rinse and dry thoroughly.” One pump provided plenty of foam for the task.

Of course, if you’re near a sink, you might simply look to see if there’s some regular old soap nearby.

Independent health and science journalist, former editor-in-chief of LiveScience, writing about how we age and how to optimize your mind and body through time.

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