Since the appearance of Covid-19 sales of hand sanitizer gels have exploded. This product has become so sought after that a shortage has occurred, forcing the French government to take measures to control prices and allow dispensing pharmacists to produce them themselves. In the United States, New York State has announced that it will also start producing its own hand sanitizer to meet demand, while drugstore and supermarket managers have started to limit the quantities that can be purchased. .
But be aware that while these disinfectants can help reduce the risk of getting certain infections, not all of them are as effective against coronaviruses as each other.
Although a recent study has suggested that the new SARS-CoV-2 coronavirus can be transmitted through feces, its main route of spread is similar to that of other respiratory viral infections such as colds and flu: droplets loaded with viruses thrown from the mouth or nose of infected people contaminate healthy people nearby.
In addition to inhalation of droplets, it is also possible to become infected by touching a surface or an object contaminated by the virus, then by putting his hands to his face, in particular at the level of the mouth or the nose. However, we often touch our faces without even realizing it: a study carried out in New South Wales has shown that people put their hands there about 23 times an hour.
When it comes to hand hygiene, the ultimate solution to prevent the spread of infectious diseases is washing with soap and water (hot water, not cold water). This in fact makes it possible to eliminate the oily films which cover our hands and which sometimes harbor pathogenic microbes.
Read more: Infectious diseases: do you wash your hands properly?
Hand sanitizers can also protect against these germs, especially in situations where soap and water are not available. Studies have indeed shown that they are effective in reducing not only the number, but also the kinds of microbes present on the hands.
There are two main types of hand sanitizers: alcohol-based and alcohol-free. The former contain amounts and types of alcohol (typically 60 to 95% isopropyl alcohol, ethanol, or n-propanol). In the latter, the alcohol is replaced by chemical compounds called quaternary ammoniums (usually benzalkonium chloride). These can reduce the amount of germs, but are less effective than alcohol, which is known to be able to kill most germs.
Alcohol-based hand sanitizers have been shown to kill not only many types of bacteria, including antibiotic-resistant staphylococci and pathogenic strains of Escherichia coli, but also many viruses, including the virus. influenza A, rhinovirus, hepatitis A virus, HIV, and Middle East respiratory syndrome coronavirus.
Alcohol attacks and destroys the envelope protein on the surface of certain viruses, including coronaviruses. This protein is vital for the survival and multiplication of said viruses.
To be able to kill most viruses, a hand sanitizer must contain at least 60% alcohol. Hand sanitizers that contain less than 60% alcohol are not only less effective against viruses, but also against bacteria and fungi; they only reduce the growth of germs instead of killing them completely.
In addition, even hand sanitizers containing 60% alcohol are not able to kill all types of germs. Studies have shown that to eliminate nor are viruses, responsible for gastroenteritis, these disinfectants less effective than washing hands. The same goes for Cryptosporidium (a parasite that causes diarrhea), and Clostridium difficult (a bacteria that causes intestinal problems and diarrhea).
The shortage of hydro alcoholic gels having led some people to try to make their own hand sanitizers, it is also important to know that these products may not be as effective as those available on the market.
Also, if your hands are covered in grime, washing them with soap and water is more effective than using alcohol-based hand sanitizers. Research has shown that the detergent effect of soap and friction during washing combine to reduce the number of germs on the hands, and remove dirt and organic matter.
Another important point: having sneezed or coughed in your hands, a spray of hydro alcoholic gel could prove to be insufficient to disinfect your hands. Indeed, the latter can then be contaminated with mucus, but this protects microbes and could limit the effect of the disinfectant.
Therefore, the best way to prevent the spread of the coronavirus and to reduce the risk of contracting it is to wash your hands with soap and warm water. And avoid touching your face as much as possible.
However, without soap and water, hand sanitizers containing at least 60% alcohol are a practical alternative. If you have to use them, make sure you use them correctly: like when washing with soap and water, make sure you cover your hands completely (including between your fingers, wrists, palms, and the back of the hand and the nails) then rub carefully, for at least 20 seconds. This is the sine qua non condition for the use of this type of product to be truly effective.