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Take plain liquid soap, and apply in a dime-sized drop on your hands; rub with water over palms, fingers, and up to one’s elbows for at least 20 seconds, then rinse thoroughly with clean water. It lacks the dramatically biting, corrosive, “ah, we’re killing germs!” odor of 79% rubbing alcohol or chlorine bleach, but spending less than a minute manipulating an unassuming bottle of hand soap at the sink deploys one of the most effective weapons in our arsenal against viral and bacterial infections. Is soap really that powerful?

Nurses know that the efficacy of hand-washing has long been established by science and that ordinary hand soap—unaccompanied by any additional “germ-fighting” anti-bacterial ingredients—easily destroys more viruses and bacteria than even the costliest hand-sanitizers. But how does it work? Here are some facts that might help your patients understand why they need to spend quality time at the sink.

How Does Soap Work?

Soap is a surfectant. When combined with water, surfectants help the water to spread out and cover surfaces—whether hands, counter-tops, dishes, or clothes—so they can be thoroughly cleansed. In effect, surfectants are a tool for removing germs (i.e., bacteria, viruses, fungi, and protozoa that can cause disease).

As we go about our business, germs on the surfaces and people we touch adhere to the oils on our hands. Water on its own cannot penetrate oils, but rubbing your hands with both soap and water breaks down the oils, which carry germs away as you rinse your hands. The key is in the action of surfectants against oil and dirt. Soap molecules have hydrophilic heads that cling to water molecules and hydrophobic tails that avoid water molecules. When mixed with water, soap molecules form into tiny hydrophobic balls called micelles. As the micelles move across the surface being cleaned, they attract and absorb oils and fats (along with the germs and dirt clinging to those oils and fats). When you rub your hands with soap and water and rinse them under the tap, the clean water carries soap, oils, and germs down the drain.

Soap v COVID-19

breaks down coronaviruses. During the process of hand-washing, according to National Geographic, soap “pries open the coronavirus’s exterior envelope and cause[s] it to degrade. These soap molecules then trap tiny fragments of the virus, which are washed away in water.”

Hand-Washing is an Ancient Practice, but Hand Hygiene is a Modern Development

Humans have been using soaps made from fats, oils, and salts for millennia, but even the efforts of Florence Nightingale failed to convince many people that hand-washing reduces the spread of infection. In fact, it was a 1980s series of food-borne and other infectious outbreaks that prompted the CDC to establish hand hygiene guidelines!

Quote: “Soaps were not to be found in early Ancient Roman baths; even Cleopatra was confined to essential oils and fine white sand (as an abrasive) for cleansing.” –Open University, The History of Soap-Making

Liquid v Bar?

Everyone has at some point faced a gray, gunky bar of soap sitting in a scummed dish and wondered. Quis custodiet ipsos custodes? Or in this case, “who cleans the cleaners?” Despite the dire optics, scientists believe that any soap—yes, even that nasty lump sitting beside your brother’s bathroom sink—is more sanitary to use than no soap at all. In two studies—one in 1965, and another in 1988—researchers actually applied biological contaminants to bars of soap and found that bacteria did not adhere to users’ hands after the washing process. The 1988 study stated, “After washing, none of the 16 panelists had detectable levels of either test bacterium on their hands.” No evidence has emerged to contradict these studies, and the CDC recommends either bar or liquid soaps as a defense against infection.

Regular v Antibacterial?

There is no need to waste money on “anti-bacterial” soaps. The Minnesota Department of Health bluntly states, “Antibacterial soaps are no more effective than plain soap and water for killing disease-causing germs outside of health care settings. There is no evidence that antibacterial soaps are more effective than plain soap for preventing infection under most circumstances in the home or in public places.”

Hand Sanitizer or Soap and Water?

Alcohol-based hand sanitizers are a very convenient substitute for soap and water, but they do not serve as a full-time alternative. Scientists at the CDC decidedly prefer old-fashioned scrubbing: “Soap and water are more effective than hand sanitizers at removing certain kinds of germs… 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.” They also warn, “When hands are heavily soiled or greasy, hand sanitizers may not work well.”

Healthcare providers are an exception, though. The CDC notes that “hand sanitizers work well in clinical settings like hospitals, where hands come into contact with germs but generally are not heavily soiled or greasy.” They recommend that HCPs use sanitizers with 60-95% alcohol “unless hands are visibly soiled,” and add that “an alcohol-based hand rub is preferred over soap and water in most clinical situations due to evidence of better compliance compared to soap and water.”

Are “Scrubbing Bubbles” Really a Thing?

A soap bubble is made up of two layers of soap molecules with a thin layer of water between them. But does it have a practical use during the cleaning process? From a hygiene standpoint, lather is a useful visual cue as you scrub your hands and it can help create more friction as you rub a surface, but it does not play an active role in cleansing. Even though it is known that hard water creates less lather than soft water, cleaning with either is equally effective. However, most people find lather appealing, so if lather encourages hand-washing it does have value, as long you remember to rinse thoroughly!

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Koren Thomas
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