What is water-free hand sanitizer, can it really keep your hands away from germs?

2020-04-25 01:30:23 movie 719℃

Text/Laura Howes

Translated by Wei Xinyu

At the beginning of 2020, with the spread of the new coronavirus SARS-CoV-2, the sales of water-free hand sanitizers began to increase. On March 11, the World Health Organization officially upgraded the epidemic to a global pandemic. Health agencies around the world recommend that people not touch their faces and wash their hands after touching public areas such as doorknobs and staircase handrails.

The first case of New Coronary Pneumonia (COVID-19) in the United States was discovered on January 20. According to market research firm Neilsen, the sales of water-free hand sanitizer in the United States increased by 73% in the four weeks from that day to February 22.

Signs explaining to customers that the hand sanitizer has been sold out appeared at the door of stores all over the world. Therefore, the French Moet Hennessy Louis Vuitton Group (LVMH), the owner of the luxury jewelry brand, the chemical giant BASF, and chemistry students in universities around the world are all trying to produce new supplies.

But has the popularity of water-free hand sanitizer recognized? Although most health officials claim that soap and water are the best way to keep your hands free from the virus, experts say that when there is no sink near you, water-free hand sanitizer is the next best way. In order to maximize the benefits provided by the water-free hand sanitizer, the US Centers for Disease Control and Prevention recommends that people use a product containing at least 60% alcohol. Let the water-free hand sanitizer cover the entire surface of the hands, and then rub it on the hands until dry until.

Before scientists knew the existence of germs, doctors connected hand washing with health. The American medical reformer Oliver Wendell Holmes and the Hungarian doctor Ignaz Philip Semmelves, who is respected as the "mothers’ savior", both treated unhygienic hands in the 1840s. The increase in the incidence of puerperal infections is linked to the fact that it was only nearly 20 years later that the famous French biologist Louis Pasteur published his findings on the theory of disease bacteria for the first time. In 1966, Lupe Hernandez, a nursing student, applied for a patent for an alcohol-based, gel-based, water-free hand sanitizer for hospital use. In 1988, the company Gojo introduced Purell, the first alcohol-based gel-type hand sanitizer for consumers to the market.

Although some commercially available water-free hand sanitizers do not contain alcohol, most of the water-free hand sanitizers currently available are mainly composed of alcohols. This is because alcohol is both a very effective disinfectant and can also be safely applied to the skin. The role of alcohol is to break the outer shell of bacteria and viruses.

The new coronavirus SARS-CoV-2 is called an enveloped virus. Some viruses only use protein cages to protect themselves, but when enveloped viruses leave their infected cells, they wrap themselves in their shells. The shells are part of the lipid cell membrane and the infected cells. The protein of the virus itself. According to Pall Thordarson, a chemist at the University of New South Wales, the lipid bilayers surrounding enveloped viruses such as the new coronavirus are connected by hydrogen bonds and hydrophobic interactions. Similar to lipids that protect microorganisms, alcohol molecules have both polar and non-polar regions. So, as Soldasson said, "Ethanol and other alcohols will disrupt the supramolecular force and effectively'dissolve' lipid membranes. But he added that we need a fairly high concentration of alcohols to quickly break down microorganisms. This is why the US Centers for Disease Control and Prevention recommends using a hand sanitizer containing at least 60% alcohol.

But rubbing a high concentration of alcohol on the skin is not so pleasant. Alcohol will Dry skin quickly, because they also disturb the protective oil layer on our skin. This is why water-free hand sanitizers contain moisturizers to counteract this dry skin effect.

World Health Organization provides two A simple formula (https://www.who.int/gpsc/information_centre/handrub-formulations/en/), used in resource-limited or remote areas, when people do not have access to hand sinks or other facilities for cleaning hands We make our own water-free hand sanitizer. One of the formulas contains 80% ethanol, and the other contains 75% isopropanol, also known as antiseptic alcohol. These twoThe formulas contain a small amount of hydrogen peroxide and glycerin, the former is used to prevent the growth of microorganisms in the hand sanitizer, and the latter is used to help moisturize the skin and prevent dermatitis. Other wetting compounds that can be found in water-free hand sanitizers include polyethylene glycol and propylene glycol. When ethanol-based hand sanitizer is applied to the skin, the ethanol in it dissipates, leaving behind these soothing compounds.

In the clinic, a liquid, flowing, water-free hand sanitizer, just like the kind you can prepare through the formula of the World Health Organization, can be easily distributed to patients, doctors and visitors from the extruder hung on the wall Hands. For consumers, the gel-like water-free hand sanitizer is easier to carry and use because the gel is easier to squeeze out of the bottle without spilling it everywhere. Gels can also slow down the volatilization rate of alcohol, ensuring that they have a world over our hands and fight against possible microorganisms.

Those who have tried homemade gel-like water-free hand sanitizers will tell you that classic gelling agents, such as gelatin and agar, do not work when mixed with high-concentration alcohols needed to kill bacteria and viruses. effect. The reason why these reagents cannot form a stable gel is because the polar hydroxyl structure in the alcohol disrupts their intermolecular interaction. The way for water-free hand sanitizer manufacturers to overcome this obstacle is to use high molecular weight and cross-linked polymer polyacrylic acid. Cross-linking based on covalent bonds can resist interference from alcohol to form a viscous colloid.

Although most hand sanitizers contain ethanol or isopropanol, alcohol-free hand sanitizers are also available. Such products usually contain antibacterial compounds such as benzalkonium chloride, which can provide continuous protection against bacteria. However, the US Centers for Disease Control and Prevention does not recommend the use of alcohol-free hand sanitizer products to combat the new coronavirus, because it is unclear whether they can successfully kill the new coronavirus.

So you should check the shelves of your local store regularly like a devout believer until the hands-free hand sanitizer is restocked, or buy them out as soon as they are available? According to Rachel McCloy, an expert in behavioral sciences at the University of Reading, panic shopping allows people to regain a sense of control. But when people are frightened, they are usually unable to make rational or risk-compliant decisions. She said: "The key point is to follow the guidance of experts in the field of public health and understand the most effective action you can take at any moment." The best option is still to wash your hands.

Soldasson emphasized that washing hands with soap and water is still the best way to maintain hand hygiene. Soap molecules not only disrupt the non-covalent bonds that hold the cell walls of viruses and bacteria together, but they can also surround microorganisms and remove them from the skin. Water-free hand sanitizer cannot remove microorganisms from the skin, nor is it effective for all pathogens. For example, the Norovirus that causes acute gastroenteritis does not contain a lipid membrane protective layer that can be destroyed by alcohol, while the spores of Clostridium difficile have a strong keratin shell that can protect them for several years. In addition, when the hands are dirty or full of grease, alcohol cannot work effectively.

"Products based on alcohol are effective," Soldasson said, "but nothing can compare to soap."