Sanitizers vis-a-vis soaps: What, when, and why?

The advent of COVID-19 has certainly put our lives to halt. The world’s health care system is currently battling against this novel virus. In the scenario where scientists all around the world are working day and night to find a vaccine against the virus, all of our combat strategies are currently based on preventive measures. Now our lives revolve around personal hygiene and “Washing our hands” regime. Soap and hand sanitizers have become our best friends. The world has witnessed a global hysteria since the idea of quarantine emerged, leading to sanitary products including hand sanitizers going out of stock and soap sales skyrocketing. Accounting for this hysteria, we began using the two products of our concern, soaps and hand sanitizers, interchangeably. But can we do so? 
Here, we will try to decipher the scientific basis of their working and efficacy against the novel coronavirus in simple terms. 

The Cosmopolitan Virus

On 11 March 2020, WHO declared COVID-19, the first pandemic caused by a coronavirus, which is a highly transmissible infection with no foolproof cure, leaving preventive measures as our last resort. COVID-19 (CoronaVirus disease- 2019) is caused by SARS-CoV-2 (called so because it belongs to the same family of viruses that cause SARS). The name of the virus is derived from the Latin word corona (which itself has a Greek origin), meaning crown, owing to the crown-shaped proteins visualized in electron micrographs. The Novel coronavirus contains positive-sense single-stranded RNA as its genetic material, that is, the RNA is directly readable by the host ribosomes into proteins (seems like less work for the virus, right?). The virus is enveloped by a host-cell derived lipid membrane; it is this membrane that is targeted by soaps and sanitizers. The lipid bilayer consists of two layers of lipid molecules (hydrophilic-water loving- head and a hydrophobic-water hating- tail) arranged in such a way that the tails interact with each other and the hydrophilic ends face the extracellular (outside the cell) and intracellular (inside the cell) spaces. Moreover, there are proteins present on this envelope, which facilitate the entry of viruses inside the host cell and play other major roles in its infectious cycle. Thus, disruption of the protective membrane and denaturation of the proteins are enough to kill the Virus.

The Dawn of Hand Sanitizers 

The importance of alcohol as a disinfectant was well known since the 12th century, which later became the backbone of the sanitizers. Tracing back the roots of the discovery of alcohol-based sanitizers, the story of Lupe Hernandez is to be found all over the internet. She is said to be a nursing student, who first formulated the alcohol-based gel sanitizers in 1966, to help doctors who couldn't wash their hands before surgeries when soap and warm water weren't available. Recently, Lemelson Centre tried to demystify the rumors around the invention. There was no patent found on this name, whereas around the same time, several other hand sanitary inventions resembling early prototypes of hand sanitizers were patented. This shows the growing concern that people were developing regarding hand hygiene during the 1960s which led people to develop several products of similar usage. Around the same time, Sterillium, the first-ever known hand disinfectant for the usage of surgeons, was invented by Peter Kalmar. By 1998, GOJO came up with Purell, US-based first commercial gel-based hand sanitizers and they shaped the sanitizers that we know today.

Understanding Sanitizers 101 

Sanitizers also called hand antiseptic or hand rub, have seen a spike in its usage in the times of pandemic. They are of mainly two types, alcohol-based (a concoction of several liquids but primarily containing some form of alcohol in it) and non-alcohol based (a concoction containing some chemicals other than alcohol for disinfection).

   

(Image by- Bharti Sootwal)

Dwelling into the working of sanitizers, the main disinfecting power of alcohol-based sanitizer lies in the alcohol used. Alcohol attacks the fatty membrane of germs, leading to its denaturation and hence killing them. To date, no virus or bacteria has been reported to retain its infectious capacity after the breakage of its membrane. Looks like they are a foolproof method to kill all sorts of germs. Well, they aren't. Alcohol does break the membrane of germs but only to a certain extent. Microbes containing thick protein-rich membranes aren't killed by alcohol single-handedly. Their growth is stopped in certain cases but alcohol fails to penetrate their membranes completely. The same goes for spores (a dormant form of microbe which is highly tough and resistant and will begin to grow again under favorable conditions). Moreover, not all pathogens contain a fatty membrane. Thus, killing these microbes becomes a difficult task for alcohol. 
Non-alcohol based sanitizers contain chemicals like benzalkonium chloride, disrupt the fatty membrane of microbes, and bores holes into it. This makes the microbe unstable and eventually leads to its killing. They also cannot work against microbes which lack the fatty membrane. 

PROS	CONS
Convenient to use, easily portable	Can’t be used in sweaty hands as it dilutes the alcohol content
Available in different forms – foams, gel, liquid	Not effective in case of soiled or greasy hands
Doesn’t cause dryness, less incidence of irritation	Highly flammable due to the high concentration of alcohol
Effective against most microbes	Alcohol poisoning due to ingestion
Doesn’t require water and sink	Ineffective in eliminating spores of  Clostridium difficile, parasites like Cryptosporidium and few viruses like Norovirus

Dating the Lather

The soaps were in the picture for a long time. Archaeologists have found evidence of soaps dating back from 2800 BC. So the Babylonians scrubbed themselves with soap, Cleopatra played with lather, and Alexander also washed with soap. The Britishers were the ones to commercialize the business of soap making and the trend seeped across the globe with time. French chemist, Nicholas Leblanc was the first to patent the process of making soda ash from common salt. Soda ash when combined with fats can lead to soap formation. This revolutionized the soap industry. Later world war I and II brought detergents into the picture. 

Something's Soapy!

Soap is a mixture of sodium salts of various naturally occurring fatty acids. This forms the basic structure of soap. Now we see different types of soaps depending upon what fatty acid is used and what other constituents are put in other to make them suitable for their application on the skin. One common type of soap that we often encounter is antibacterial soap, which often assures us with its impeccable strength to kill any germ. 99.99% percent of protection sounds very luring. Isn't it?

Soap fights off dirt and microbes by enveloping them with its sodium salts of fatty acid, also called amphiphiles. It undoes the velcro-like bond that this stuff has with our skin and washes them away from our hands with themselves. And during this process, these amphiphiles envelop air in it, resulting in the luscious lather that we all love. (Giving you another reason to wash hands. Haha!) Soaps simply wash away microbes off your hands. Are they any different from antimicrobial soaps?
The antimicrobial soaps that we use are no better than the normal soaps, rather they have their own set of side effects. They contain triclosan and triclocarban which destroy the essential microbiota of our skin, thereby killing the symbiotic microbes of our skin. Furthermore, these chemicals have been reported to cause antimicrobial resistance over repetitive usage and it is also suspected of causing cancer. 

PROS	CONS
Effective in removing dirt, grease, and chemicals	Removes natural oil and moisture from the skin leading to dryness
Works against a wider spectrum of pathogens including endospores and oocysts	Antibacterial soaps remove the useful bacteria too and lead to bacterial resistance
Lather formation and scrubbing ensures thorough cleaning of hands	Always require an ample amount of water

Coming to the Middle-ground 

We see that sanitizers as well as soaps work equally well in combating the coronavirus. The usage of either of them is governed by the conditions under which a person is. A clear distinction can’t be made as to which one is better since their working mechanism is different from each other. Depending on the type of pathogen, the effectiveness of either one of them varies. For example, in case of infection by Rhinovirus, alcohol-based sanitizers are quicker in effectively destroying them whereas it takes a much longer time to wash them off using soap and water. In the case of dirty hands or whenever we have to clean our hands then soap and water are a way out. Thus the choice of sanitizer or soap is governed entirely by the situation at hand but it is always advisable to wash our hands whenever possible.
We wish that all the readers are safe and sound. In the wake of COVID-19, the situations are worse and we hope that the world will recover from this pandemic soon. Stay safe and keep exploring!