According to the CDC and the National Institute of Public Health , washing hands with soap is considered the best way to keep your hands clean, while hand sanitizers are the next best option . Certainly more convenient when we're out and about, their mission is to reduce the amount of germs. And because we're called upon to use them every day in public transportation, restaurants, and gyms,
- How well do they work?
- What role does alcohol play in their effectiveness?
- Is it worth having our own instead of blindly trusting the packaging that they are required to provide us with?
Two seemingly contradictory studies
The truth is that whether hand sanitizers help prevent diseases caused by a respiratory virus like SARS-CoV-2 is not something that concerns science for the first time or the last time. It may be that in our country, in Europe and in the Western world in general, they have had to deal with such a situation for years, but in other regions of the planet, similar phenomena have never stopped worrying them, either due to overpopulation or weaknesses in the healthcare system.
One, perhaps the simplest, way to record the effectiveness of antiseptics is the number of days people miss work or school due to illness.
- So in 2014, a large trial conducted on kindergarten children in Thailand compared the effect of a mandatory hand hygiene program using alcohol-based hand sanitizer every hour, two hours, or before lunch on kindergarten absences due to respiratory infections. The finding was that more frequent use of sanitizer meant fewer absences .
- Quite the opposite, in the same year, a similar study conducted in New Zealand showed that the use of antiseptic had no effect on reducing respiratory infections .
What is the reason for this difference?
The first factor that can satisfactorily explain this contradiction is the type of antiseptic, since there are 2 basic categories:
- Alcohol-based hand sanitizers usually contain ethanol or isopropanol and
- Alcohol-based , where one of the main active ingredients is often benzalkonium chloride.
Of course, their separation is not that simple, as their compositions also contain other active ingredients. One only has to take a look at the official page of the Government of Canada regarding the list of disinfectants and antiseptics with evidence for use against COVID-19 .
The second factor that plays a huge role in whether a hand sanitizer is ultimately capable of killing a pathogen like coronavirus is the method of administration.
We typically find hand sanitizers in 3 different forms:
- Liquid
- Foam
- Gel
European studies on alcohol-based disinfectants have shown that in general1186/1471-2334-10-78" target="_blank" rel="noreferrer noopener"> Liquid hand sanitizers do their job better, since gels don't work fast enough. This plays a huge role in healthcare because healthcare professionals often require results in less than 30 seconds. But even the way a disinfectant is applied to the hands significantly affects its effectiveness. According to several studies, people do not cover their hands with a sufficient amount of antiseptic foam.
How much alcohol does an antiseptic really need?
Everything plays its part in this complex puzzle, but at the end of the day , what makes the difference is the amount of alcohol a hand sanitizer contains .
The CDC recommends antiseptics in which the active agent is more than 60% ethanol or 70% isopropanol , based largely on their effectiveness against viruses surrounded by a fatty outer shell, i.e. with a similar structure to SARS-CoV-2.
CDC
Of great interest, however, is a systematic review of scientific studies by Günter Kampf of the Institute of Hygiene and Environmental Medicine in Germany, where it was observed:
- At a concentration of 60%, ethanol is effective against germs in general.
- Ethanol is particularly effective at a concentration of 80% , as it will inactivate an enveloped virus within 30 seconds.
- At 43%, ethanol's real action against SARS-CoV-1, which has an identical structure to the latest coronavirus that causes Covid-19, begins . At this concentration, however, it takes perhaps a minute, during which time the alcohol could evaporate from the skin before it has time to act.
- Many people limit themselves to a few drops in the palm of one hand while rubbing their hands together for just a few seconds. Under these circumstances, 60% ethanol may not be enough.
DEFINITELY MORE THAN 60%
Washing hands with soap and water is perhaps the best way to limit the transmission of any virus. Antiseptics with more than 60% ethanol are the next best alternative , but ultimately there are several factors that affect their effectiveness. In any case, we should not neglect hand hygiene, which is the first line of defense against any pathogen.