Which Soap Is Best for Preventing Outbreaks?

With the novel coronavirus COVID-19 spreading across the world at a rapid clip, health authorities are stressing the importance of frequent hand-washing. Indeed, strategic hand-washing is one of the simplest yet most effective ways to reduce the spread of the virus and your own risk of illness.

Airport Hand Hygiene Can Significantly Reduce Pandemic Risks

As noted in a December 2019 study1 in the Risk Analysis journal, which investigated the spread patterns of flu-type viruses, intercontinental flights allow infectious pathogens to spread like wildfire.

Aside from the speed of which an infected person can travel from one country to the next, the risk of spreading pandemic disease is exacerbated when traveling by air for the simple reason that airplanes crowd large groups of people together in a confined space with scarce opportunities for proper hygiene.

Were people to more frequently wash their hands during travel, the risk of pandemic infection could be significantly reduced — by as much as 69% according to this study — which is nothing to sneeze at. As explained by the authors:2

“Here, we use epidemiological modeling and data-driven simulations to elucidate the role of individual engagement with hand hygiene inside airports in conjunction with human travel on the global spread of epidemics.

We find that, by increasing travelers’ engagement with hand hygiene at all airports, a potential pandemic can be inhibited by 24% to 69%.

In addition, we identify 10 airports at the core of a cost-optimal deployment of the hand-washing mitigation strategy. Increasing hand-washing rate at only those 10 influential locations, the risk of a pandemic could potentially drop by up to 37%.

Our results provide evidence for the effectiveness of hand hygiene in airports on the global spread of infections that could shape the way public-health policy is implemented with respect to the overall objective of mitigating potential population health crises.”

The most germ-ridden surfaces frequently touched by passengers at airports and inside aircraft include self-service check-in screens, gate bench armrests, railings, water fountain buttons, door handles, seats, tray tables and bathroom handles. The 10 key airports with the greatest infection spread rate, according to this study, are:

Face-Touching Is a Vector for Disease Transmission

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Frequently washing your hands during influenza season and other pandemic outbreaks is a crucial safety measure, in part because most people touch their face an average of 23 times per hour.3

As noted in the American Journal of Infection Control,4 habituated face-touching behavior is a vector for self-inoculation and transmission of infectious diseases. In other words, each time you touch your face, you run the risk of introducing disease-causing pathogens into your body as they transfer from your hands to your face. According to this study:5

“On average, each of the 26 observed students touched their face 23 times per hour. Of all face touches, 44% involved contact with a mucous membrane, whereas 56% of contacts involved nonmucosal areas. Of mucous membrane touches observed, 36% involved the mouth, 31% involved the nose, 27% involved the eyes, and 6% were a combination of these regions.”

The take-home message here is that mouth, nose and eye touching is a common, and largely unconscious, behavior by which infectious diseases are spread. The remedy for this behavior is to make sure you wash your hands on a regular basis, and especially after certain activities, such as:

  • Anytime you visit a health care facility — Before entering a patient’s room and before leaving the premises, be sure to wash your hands. An estimated 1 in 4 patients also leave the hospital with a superbug on their hands, suggesting patients also need to become more mindful about hand-washing when in a health care setting6
  • Directly before you eat
  • After you’ve used the restroom, and after each diaper change
  • Before and after caring for someone who is ill, and/or treating a cut or wound

When out in public, the opportunities for picking up germs on your hands are incalculable. Door knobs, door and cart handles, counters, railings, airport security bins — every conceivable surface has the potential for contamination.

Get Into the Habit of Cleaning Your Cellphone Too

Cellphones, by the way, are another significant vector of infectious disease. Even if you wash your hands frequently, as soon as you touch your cellphone you’ve contaminated your hands again and can deposit those germs on everything you touch.7

So, getting into the habit of regularly cleaning your cellphone would be in your best interest too. For instructions on how to safely sanitize your cellphone, see the video above.

PC Magazine suggests using alcohol-containing lens wipes, typically used for cleaning camera lenses. Also, remember to wipe down the case of your phone, and pay attention to the back if you use a fingerprint reader to unlock your phone.

Proper Hand-Washing Technique

Now, even people who wash their hands on a regular basis may not do it correctly, thus missing an important opportunity to quell the spread of germs. To make sure you’re actually removing the germs when you wash your hands, follow these guidelines:

  1. Use warm water
  2. Use a mild soap
  3. Work up a good lather, all the way up to your wrists, for at least 20 seconds
  4. Make sure you cover all surfaces, including the backs of your hands, wrists, between your fingers and around and below your fingernails
  5. Rinse thoroughly under running water
  6. Dry your hands with a clean towel or let them air dry
  7. In public places, use a paper towel to open the door as a protection from germs that the handles may harbor

Why Soap Is Most Effective Against Viruses

You also want to make sure you’re using the most effective products. Contrary to popular belief, antibacterial soap is NOT ideal for killing disease-causing viruses on your hands. Like antibiotics, antibacterial soap only affects bacteria, not viruses. Homemade Hand Sanitize... Smith, Rebecca Buy New $8.99 (as of 09:37 EDT - Details)

Even for bacteria, research has demonstrated that antibacterial soap provides no additional benefit over nonantibacterial soap. As noted in a 2007 systematic review8 published in the journal Clinical Infectious Diseases:

“The lack of an additional health benefit associated with the use of triclosan-containing consumer soaps over regular soap, coupled with laboratory data demonstrating a potential risk of selecting for drug resistance, warrants further evaluation by governmental regulators regarding antibacterial product claims and advertising.”

When it comes to viruses, regular soap works the best. As detailed in a series of Twitter posts9 by professor Palli Thordarson,10 who specializes in bio-mimetic, supramolecular and biophysical chemistry and nanomedicine, soap very effectively kills the COVID-19 virus, “and indeed most viruses.”

The reason for this is because the virus is “a self-assembled nanoparticle in which the weakest link is the lipid (fatty) bilayer.” Soap dissolves this fat membrane, causing the virus to fall apart, thus rendering it harmless. Not even alcohol is as effective for inactivating viruses, although it may be more practical for using surfaces other than your hands and body.

Soap Mechanics 101

A soap molecule is suited for mixing oil and water as it shares qualities of each. Soap molecules are amphipathic,11 meaning they have both polar and nonpolar properties, giving them the ability to dissolve most kinds of molecules.

As noted by Thordarson, the amphiphiles (fat-like substances) in soap are “structurally very similar to the lipids in the virus membrane,” so “soap molecules ‘compete’ with the lipids in the virus membrane.” In short, the soap dissolves the “glue” that holds the virus together.

The alkalinity of soap also creates an electric charge that makes the soap hydrophilic (water-loving).12 Hydrogen atoms in water molecules have a slightly positive charge, so when you wet your hands and then use soap, this molecule will readily bond with the nearest water molecule. Hence, when you wash your hands under running water, the now deconstructed virus is easily washed away. The New York Times explains the process this way:13

“When you wash your hands with soap and water, you surround any microorganisms on your skin with soap molecules.

The hydrophobic tails of the free-floating soap molecules attempt to evade water; in the process, they wedge themselves into the lipid envelopes of certain microbes and viruses, prying them apart.

‘They act like crowbars and destabilize the whole system,’ said Prof. Pall Thordarson, acting head of chemistry at the University of New South Wales. Essential proteins spill from the ruptured membranes into the surrounding water, killing the bacteria and rendering the viruses useless.”

Using Alcohol-Based Disinfectants

The U.S. Centers for Disease Control and Prevention recommends washing your hands with soap and water. Only when soap and water are unavailable are alcohol-based hand sanitizers recommended. As noted on the CDC website:14

“Many studies have found that sanitizers with an alcohol concentration between 60–95% are more effective at killing germs than those with a lower alcohol concentration or non-alcohol-based hand sanitizers.

Hand sanitizers without 60-95% alcohol 1) may not work equally well for many types of germs; and 2) merely reduce the growth of germs rather than kill them outright.

When using hand sanitizer, apply the product to the palm of one hand (read the label to learn the correct amount) and rub the product all over the surfaces of your hands until your hands are dry.”

As noted by Thordarson, the drawback of ethanol and other alcohols is that they cannot dissolve the lipid membrane holding the virus together. This is precisely why soap and water works best.

That said, a 2017 review15 in the Journal of Hospital Infection found 80% ethanol solutions were “highly effective” against 21 different viruses within 30 seconds, although some viruses (poliovirus type 1, calicivirus, polyomavirus, hepatitis A virus and foot-and-mouth disease virus) were hardier and required a 95% solution.

According to the authors, “The spectrum of virucidal activity of ethanol at 95% … covers the majority of clinically relevant viruses.” A hand sanitizer with an alcohol content of at least 60% is also thought to eliminate the COVID-19 virus.16

Just keep in mind that frequent use of alcohol-based products is rough on your skin and can dry it out. This could actually make things worse, as cracked skin renders you more susceptible to infection, as it provides germs a perfect entryway into your body.

Does Bar Soap Harbor Germs?

Another common misconception is that liquid soap is more hygienic than bar soap, since many different hands might touch a single bar of soap. The fear that bar soap may harbor germs is unfounded, however. While occasional studies have documented environmental bacteria on bar soap, no study has demonstrated bar soap to be a source of infection.17

The first rigorous study to look into this question was published in 1965.18 Researchers intentionally contaminated their hands with nearly 5 billion bacteria, including disease-causing strains such as staphylococcus and E. coli.

They then washed their hands with bar soap, after which a second person washed with the same bar of soap. The second person’s hands were cultured and researchers found the bacteria were not transferred. The researchers concluded:19

  • Bar soaps do not support the growth of bacteria under usage conditions
  • Bar soaps are inherently antibacterial by their physical-chemical nature
  • The level of bacteria that may occur on bar soap, even under extreme usage conditions (heavy usage or poorly designed nondrainable soap dishes), does not constitute a health hazard

Nearly 20 years later, another study20 (sponsored by a soap manufacturer) confirmed these findings. Here, they inoculated bars of soap with pathogenic bacteria; 16 participants washed their hands with those bars. After washing, none of the participants’ hands had detectable levels of bacteria.

According to the researchers,21 “little hazard exists in routine hand-washing with previously used soap bars and support the frequent use of soap and water for hand-washing to prevent the spread of disease.”

Towel Dry or Air Dry — Which Is Better?

Many believe using an air dryer is preferable to using a towel when in a public restroom. Surprising as it may seem, air dryers may actually spread far more germs than paper towels.

In the 2017 paper “Cleanliness in Context: Reconciling Hygiene With a Modern Microbial Perspective,”22,23 microbial ecologists at the University of Oregon examine different methods of hand drying, noting that “most research has shown that warm air dryers may increase the number of bacteria on the hands after use.” The reason for the increase in bacterial load is thought to be due to:

  • Bacteria inside the dryer mechanism being blown out during use
  • Bacteria-enriched air being recirculated
  • Bacteria found in the deeper layers of skin being liberated when rubbing your hands together beneath the hot air stream
  • Some combination of the above

Other research24 found high-speed jet dryers spray 1,300 times more viral material into the surrounding area than paper towels, dispersing the viral load up to 10 feet from the dryer.25,26 A 2012 meta-analysis in Mayo Clinic Proceedings, which looked at a dozen studies, came to a similar conclusion, noting:27

“Most studies suggest that paper towels can dry hands efficiently … and cause less contamination of the washroom environment. From a hygiene viewpoint, paper towels are superior to electric air dryers. Paper towels should be recommended in locations where hygiene is paramount, such as hospitals and clinics.”

The take-home message here is that when using a public restroom, you may be better off forgoing the air dryers and using a paper towel instead. Be sure to dispose it properly, in the trash bin, and use a clean paper towel to open the door when exiting.

The drawback of paper towels is the environmental impact. In the video below, Joe Smith of Oregon outlines how you can reduce the amount of paper towels you use, while still getting your hands dry. Two key points: First, shake your hands to eliminate as much water as possible. Next, fold the paper towel to increase absorbency.

Avoid Cloth Towels and Rags During Pandemics

Cloth towels are the least hygienic alternative during influenza season or pandemics, as they have the highest risk of cross-contamination. According to a 2014 University of Arizona study,28 towels may be the most germ-ridden item in your home.

Tests revealed a staggering 89% of kitchen towels and nearly 26% of bathroom towels were contaminated with Coliform bacteria — microbes associated with food poisoning and diarrhea. The primary reason for this is the moisture cloth towels retain, which serves as a perfect breeding ground for germs.

Moist towels and rags are also hospitable places for viruses. As noted in a 2012 study29 in Applied and Environmental Microbiology, cloth rags can easily spread viruses from one surface to another.

So, when sanitizing your home (which is advisable when someone in the household is ill), it’s best to use a paper towel. Once the immediate risk of infection has passed, you can go back to using reusable rags for everyday cleaning.

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