Sanitiser has been a sell out product this year, but do you know how it actually works?

Most hand sanitisers use one key ingredient, alcohol [1]. Alcohols are organic molecules made of carbon, oxygen and hydrogen[1]. Sanitisers usually use three types: ethanol (the stuff we find in alcoholic drinks), isopropanol (rubbing alcohol) and n-propanol [1], [2]. They are most useful as they attack a wide range of microbes that we don’t like such as bacteria and viruses. Now, let’s find out how.

Let’s start with viruses. There are many different viruses, but we will break them down into two types: enveloped and non-enveloped [2]. Most sanitisers are not effective against non-enveloped viruses, but luckily most harmful viruses are enveloped [2]. Enveloped viruses (including COVID-19)[3] have a protective coat all around them called a lipid membrane. This lipid membrane is important for our antiviral mechanism [2].

The outer section of the lipid membrane is similar to water and the inner section is similar to fat [2]. This is why alcohol is perfect for the job! Alcohols have both hydrophilic and lipophilic properties; hydrophilic means it can dissolve in water and lipophilic means it can dissolve in lipids (fats) [4], [5]. These properties allow them to disrupt and dissolve the lipid membrane. The hydroxyl (oxygen and hydrogen) part of the alcohol dissolves in water and the rest of the alcohol dissolves in the fat [2]. This causes the membrane to interact with the alcohol instead of holding itself together. Once this has happened, proteins on the surface of the virus that are necessary in its action are also disrupted and destroyed by the alcohol [2]. This destruction of protein is called protein denaturation. The figure below shows this process with COVID-19.

Figure 1: Alcohol mechanism of action against COVID-19 [5]

Like enveloped viruses, bacteria also have a lipid membrane surrounding them [2]. Bacteria are very diverse and come in all shapes and sizes, however they usually have a plasma membrane to keep everything in and an outer cell wall for protection [2]. Just like with viruses, the alcohol dissolves the bacterial membrane [2]. This is like something dissolving our skin, the bacteria is ruptured and it can no longer live. It is also thought that alcohol inhibits protein synthesis [2]. If a bacteria can’t produce protein, it cannot function. If alcohol irritates your hands then there is always another option. Benzalkonium chloride (BC) is an alternative ingredient that is often used in non-alcohol based sanitisers [2]. This also targets the lipid membrane, but in a slightly different way. Think of the BC as having a head and a tail [2]. The head of BC is positive charged and is slowly attached to the lipid part of the membrane [2]. This reduces its fluidity and creates space for the tail to enter the membrane [2]. All of this disruption stops protein function, causes the lipid membrane to dissolve and kills the microbe.

Author : Jane Landeg