Rithish Ninan Alex, Victor D’Souza and Avishkar Raut,
St. Xavier's College (Autonomous),
Mumbai, Maharashtra, India
The chemistry behind hand washing
As we all well know, the past few months we have locked inside our homes, because of a virus which we knew as the 'coronavirus'. As the pandemic started, various biological scholars stated it is best to wash our hands with soap or hand washing liquid than using other things. We’ll think why was that necessary or what is the chemistry behind it? So first let's start with the structure of the soap molecule, basically a soap as two-component, a hydrophobic part (tail) and hydrophilic part(head). So, the hydrophobic part is water-fearing such that it does not mix with water rather it prefers to bind with oil or fats while the hydrophilic part easily gets dissolved in water. Secondly, we’ll try to know about how it works: when soaps are mixed in water, a small round globular structure known as micelles is formed with the tail (hydrophobic part) facing inward. The tail part of the soap molecule clings itself into the bilayer membrane of the micro-organism (as most of the viruses and bacteria are made off fatty acid membrane) which tore these membranes apart and demolish it completely or to the dirt. In order to increase the hydrophobic effect, we can use warm water to wash hands. Moreover, it is advisable to wash hands with soap or hand washing liquid for 20-30 sec as it gives the hydrophobic part some time to attach themselves with the dirt or the pathogen and a complete cleansing can be done.
The activity of Handwash against a microbial organism
In the year the 1950s and 1970s in the UK and the United States, respectively, chlorhexidine gluconate was developed, was found to have a good safety record. Chlorhexidine doesn’t get dissolved in water completely. The chlorhexidine disrupts the cytoplasmic membrane, which leads to tithe precipitation of cellular content. However, the antimicrobial activity of chlorhexidine is much slower than the antimicrobial activity of alcohol. It doesn’t deal effectively with mycobacteria, fairly or satisfactory with fungi but quite profoundly deals with bacteria having gram-positive category. However, because of the absence of sporicidal, it couldn't show the in-vitro activity against viruses having an envelope. The antimicrobial activity of chlorhexidine remains unaffected by organic compounds and even blood.
Chloroxylenol was developed in Europe in1920, known as a para-chloro-meta-xylenol (PCMX) is a halogen-substituted phenolic compound. Chloroxylenol does the work of inactivating the bacterial enzymes and makes drastic changes in the cell wall. However, chloroxylenol shows very positive activity against those bacteria that are gram-positive in nature and their activity is fair enough against gram-negative, mycobacteria, and some viruses. Nonetheless, it is less active against P. aeruginosa. but the addition of ethylenediaminetetraacetic acid (EDTA) makes the chloroxylenol more efficient against P.aeruginosa
Hexachlorophene was developed in the years of 1950s. Bisphenol gets manufactured by two and three phenolic and chlorine moieties respectively. It does the work of directly pertaining to neutralizing the crucial enzymes located inside various microorganisms. After washing our hands with a good amount of handwash the residual activity lasts for several hours. It is efficient and convenient for users. After repeated uses, the number of bacteria on our hands is reduced. After continuous use of 3% hexachlorophene preparation, the drug gets absorbed through our skin.
Hand wash is very essential in our daily lives as it helps us fight against microbial organisms, especially since we are living in a pandemic. Antiseptics and disinfectants such as chlorhexidine, chloroxylenol, and hexachlorophene are used in hand washes. For complete cleansing of our hands, we should wash them for 20-30 seconds with warmer water. Washing of hands drops the bacterial count to 99.9%.
Clark, C. 2020, getting back to chemistry basics: How simple soap can save lives
Pittet D. 2005 Geneva’s University Hospitals of Medicine, Geneva; Switzerland