The Science of Hand Sanitisers

  Sorit Gupto |     April 22, 2020

The Corona virus or COVID-19 is the talk of the town. And thanks to the tsunami of messages we receive daily on our smartphones, there is no dearth of misinformation, rumors and gossips about the virus. So, how do we know which information is credible? For example, take the hand sanitiser.

It has suddenly become one of the biggest tools of the 'culture corona'. Yet, in most medicine shops, a 50 ml bottle of hand sanitiser has become a rarity. Several shops have run out of them and are now selling bigger bottles, some of which cost as much as Rs 500! Needless to say, manufacturers of hand sanitisers are making a fortune because of this sudden rise in demand.

Prescribed as one of the basic precautions one can take to avoid the spread of corona virus, the hand sanitiser has acquired prime importance at a time when there are rising cases of corona infections around the world. But what makes this little bottle so important, especially now? Well, let us look at the chemistry of it.

The active ingredient of a hand sanitiser is alcohol. A regular solution or bottle contains around 70 per cent of alcohol. However, the type of alcohol used can vary. Ethanol, the chemical present in most alcoholic drinks, is used in many hand sanitisers, but there is one difference. The alcohol content in hand sanitisers is very high as compared to alcoholic beverages. Besides ethanol, isopropanol or n-propanol is another alcohol that is used in hand sanitisers.

Killing bacteria and viruses

Bacteria and viruses have an outer coating, which is made of protein and lipids. The alcohol molecule disrupts and eventually explodes this outer coat of bacteria and viruses. And that’s the end of the pathogen. Antibiotic-based soaps can also be used for cleaning hands but unlike alcohol-based solutions, they target a specific point of a pathogen's life cycle. Moreover, there is always a chance that the bacterium or virus develops antibiotic-resistance because of the soap. Since the alcohol molecule destroys bacteria and viruses by rupturing their outer membrane, resistance is not a problem with alcohol-based hand sanitisers. There is no way for bacteria and viruses to develop resistance to the effects of alcohol on their proteins and membranes.

Ethanol and isopropanol, however, have one drawback. They can dry the skin. To counter this effect, manufacturers add glycerol, a type of alcohol, in hand sanitisers. Chemically speaking, glycerol is also an alcohol, but it’s not added in solutions/disinfectants to kill germs. Rather, it is added to increase the thickness of the solution. This makes it more potable and easier to use. Some brands also add tocopherol, an alcohol rich in Vitamin E which is good for the skin. Colours and fragrances can be added as well. These are not necessary for the hand sanitiser to work, but they make your hands smell nice. And now comes the funniest part. Manufacturers typically add some bad–tasting compounds in the hand sanitiser. Why? Well, this is done to stop people from consuming it as a drink. After all it’s alcohol. Hick!

Now, one may wonder if this chemical goo really kills 99.99 per cent of germs? Well, first of all we need to be careful that we don't fall prey to such marketing gimmicks of manufacturers. The effectiveness of a hand sanitiser varies depending on how dirty our hands are and most importantly, what kind of pathogen it is being used upon. In other words, it is not a magic potion that can eliminate the threat of infection entirely.

Another important fact is that hand sanitisers do not remove dirt. For that we need soap and water. Doctors, therefore, advise that it is best to use hand sanitisers in combination with regular hand washing.

About the Author

Supplement Editor, Gobar Times (2016-2021)

Content tags