Coronavirus: not all hand sanitizers are effective

By Manal Mohammed, University of Westminster

Since the COVID-19 outbreak originated, sales of hand sanitizers have skyrocketed. They have become such a sought-after product that pharmacies and supermarkets have begun to limit the amount of gels that customers can purchase each time they visit stores. New York State has even announced that it is going to start making its own hand sanitizer to meet existing demand. While disinfectants can help reduce the risk of certain infections, not all gels are equally effective against coronavirus.

As with other viral respiratory infections, such as the common cold or flu, the new coronavirus (which is called SARS-CoV-2) is spread primarily through person-to-person transmission of small, impregnated droplets. of viruses that are expelled through the mouth or nose. However, a recent study indicates that it could also be spread through feces.

In addition to inhaling these tiny droplets, respiratory viruses (including SARS-CoV-2) can be contracted by coming in contact with any surface contaminated with the virus and subsequently touching your face, especially your mouth. and the nose. And, although we may not realize it, we are continually touching our faces. A study by the University of New South Wales (Australia) revealed that people touch our faces about 23 times every hour.

The most effective way to maintain correct hygiene and avoid the spread of infectious diseases is to wash your hands with soap and water. The combination of hot water (never cold) and soap eliminates fats that can harbor microbes in our hands.

Disinfectant gels, for their part, also offer protection against disease-causing microbes, especially in situations where soap and water are not available. It has also been proven effective in reducing the number and kinds of microbes that can attack us.

There are mainly two types of hand sanitizers: with alcohol and without alcohol. The former contain various types (usually isopropanol, ethanol or n-propanol) and amounts of alcohol (between 60 and 95%), a compound that has the ability to kill almost all germs.

Nonalcoholic gels contain a compound called quaternary ammonium cation (usually benzalkonium chloride) to replace alcohol. These can impair the action of microbes but are less effective than alcohol.

The effectiveness of alcohol hand sanitizers is not limited to the elimination of numerous types of bacteria, including MRSA and E. coli, they also act against a multitude of viruses, such as Influenza A virus, rhinovirus, hepatitis A virus, HIV, and Middle East respiratory syndrome coronavirus (MERS-CoV).

Fighting viruses

Alcohol attacks and destroys the viral capsid that surrounds some viruses, including the coronavirus. It is a fundamental protein for the survival and multiplication of the virus. For a hand sanitizer to kill much of the virus, it must be at least 60% alcohol.

Gels that contain a lower percentage have been found to be less effective in killing bacteria and fungi, and are likely only capable of slowing down the growth of germs rather than killing them entirely.

Even disinfectants containing 60% alcohol do not guarantee the elimination of all types of germs. Some research has found that washing your hands is more effective than applying disinfecting gels to kill the norovirus, the Cryptosporidium (a parasite that can cause diarrhea) and Clostridioides difficile (a bacterium that causes intestinal problems and diarrhea).

Seeing the scarcity that characterizes this product during these days, some people have decided to make their own hand sanitizers. However, it should be noted that these homemade gels may not be as effective as those found in shops and pharmacies.

If you have very dirty hands, washing with soap and water is more effective than using alcohol hand sanitizers. The studies carried out indicate that the detergent effect of soap, together with friction, is enough to reduce the amount of microbes that we house in our hands, as well as to eliminate dirt and the remains of organic materials.

Sneezing or coughing into your hand takes more than just a little gel to disinfect it. This is because at the moment when the hands become contaminated with mucosa, it acts as a protector against microbes and the disinfectant loses effectiveness in these conditions.

In short, the best and most reliable way to prevent the spread of the coronavirus (and to minimize the risk of contracting it) is to wash your hands with soap and water and avoid touching your face as much as possible.

In any case, hand sanitizers with at least 60% alcohol are considered a practical alternative when you do not have access to soap and water. If you use one of these gels, just like you would with soap and water, you should make sure to cover the entire surface of the hands (including the gap between the fingers, wrists, palms, back and nails) and rub during minus 20 seconds to obtain a comprehensive cleaning.

Manal Mohammed, Lecturer, Medical Microbiology, University of Westminster

This article was originally published in The Conversation. Read the original.