As the coronavirus spreads, disinfectants are in high demand.
Biologist Jeffrey Gardner explains why alcohol is a key ingredient in hand sanitizer and why he doesn't recommend making your own at home.
Why is alcohol the main ingredient in most disinfectants?
Alcohol is effective at killing various types of microbes, including viruses and bacteria, because it folds and inactivates their proteins. This process, called denaturation, kills microbes because its proteins fold.
Heat can also denature some proteins – for example, when you boil eggs, hardened egg whites are denatured proteins.
Alcohol is very good at killing germs.
There are different types of bacteria and viruses, and some of them are very easy to kill with alcohol. For example, E. coli bacteria, which can cause foodborne illness and other infections, are very efficiently eliminated by alcohol at concentrations in excess of 60 percent.
Differences in the outer surface of different bacteria make alcohol disinfection more effective against some of them than others.
Likewise, some viruses have an outer shell called an envelope, while others have no shell. Alcohol is effective at killing enveloped viruses, including coronavirus, but less effective at killing uncoated viruses.
Whether you're trying to kill bacteria or viruses, many studies have shown that an alcohol concentration of 60 percent or more is needed to be effective.
If 60 percent alcohol is effective against viruses, is 100 percent better?
Surprisingly, no. In fact, protein denaturation works faster when a small amount of water is mixed with alcohol. And pure alcohol evaporates too quickly to effectively kill bacteria or viruses on your skin, especially in winter when the air is less humid.
Using 100 percent alcohol will also dry out your skin very quickly and cause irritation. This can result in you not sanitizing your hands as often as necessary.
This is why most hand sanitizers contain emollients, which are blends that help soften and moisturize your skin.
Are home made disinfectants a good idea?
In my opinion, no. You can see do-it-yourself formulas online, including those that use vodka. However, vodka is usually only 40 percent alcohol. This is not enough to effectively kill germs.
Keep in mind that alcohol is volatile, which means it will slowly evaporate over time and the disinfectant will lose its ability to effectively kill viruses and bacteria.
Jeffrey Gardner, Assistant Professor of Biological Sciences, University of Maryland, Baltimore County.
This article is reprinted from The Conversation under a Creative Commons license.
Sources: Photo: Kelly Sikkema / Unsplash
