A Brief Look Into The Efficiency of Hand Sanitizer

By Erin Kang
November 25, 2020 · 3 minute read

Chemistry

Biology

Bacteria and viruses have been around infecting people since the beginning of time. One of the most common ways to transmit infections and viruses between people is through human contact, especially through hands. Hand washing and disinfecting homes is especially important in the midst of the novel coronavirus pandemic. During these unprecedented times, hand sanitizers with the most efficiency have become a hot topic.

 

Background

            Most hand sanitizers sold in stores contain some percentage of alcohol. This is because alcohol kills bacteria through the process of denaturation. Denaturation is when alcohol molecules break down a fat membrane surrounding a virus. When the fat membrane breaks down, the inside of the cell is exposed. As the critical components began to dissolve, the cell quickly dies. Most alcohol-based sanitizers contain either ethanol (ethyl alcohol) or isopropanol (isopropyl alcohol).

 

Experiment 1

The first experiment we’ll be looking at was one conducted to test the antimicrobial efficacy of 14 different hand sanitizers. The 35 healthy participants were told to wash their hands thoroughly with soap and water. Their hands were then contaminated with microbes or bacteria. Afterwards, the hands of the participants were swabbed and 10 microliters of each suspension was inoculated (introduced to a culture medium) and incubated at 37 degrees Celsius for 24 hours. Logarithmic reduction factors are used to express the number of microbes that are eliminated by disinfection. The hand sanitizers that showed the highest logarithmic reduction factors were considered to be the most effective at killing bacteria. The results showed that ethanol-based hand sanitizers were more efficient than isopropyl alcohol-based hand sanitizers.

 

Experiment 2

The second experiment tested the effectiveness of alcohol and non-alcohol-based hand sanitizers against Staphylococcus aureus and E. coli using the Kirby-Bauer method.  The Kirby-Bauer method is most widely used as an antibiotic susceptibility test. In this method, a plate is inoculated with an organism and filter paper soaked in the antibiotic is placed in the medium. As the organism grows on the plate, the antibiotic is also inhibiting the growth of the organism. The zone of inhibition demonstrates how efficient the antibiotic is by measuring the diameter of organism growth. The results showed that more alcohol composition in hand sanitizer led to an increased efficiency.  

 

Experiment 3

Another experiment evaluated the efficiency of three different disinfectant hand sanitizers. The products that were tested include Sterillium, which is a liquid and perfumed, Desderman, which is an odorless gel, and Lavit, which is a perfumed spray. Sterillium and Lavit were the most efficient in terms of inhibiting bacterial growth. Typically, alcohol (propanol 75%) in liquid form is much more effective than the gel-like form that hand sanitizer usually comes in. This is due to the fact that the liquid is able to get into the crevices, while the gel-like form simply coats the skin. Proper hand sanitizing and rubbing techniques also led to further inhibition of bacterial growth. The experimenters also found that besides the efficiency of hand sanitizer, skin compatibility is another important attribute in regards to the process of disinfection.

 

Disinfectants

            Although hand sanitizers are more effective in preventing transmission of bacteria from an individual’s hands than just plain water and soap, standard disinfectants, such as antibacterial soap and hand sanitizer might be rather scarce during these times. So, many people may turn to more unconventional forms of disinfectants. Hydrogen Peroxide is considered to be a strong disinfectant. The chemical formula of Hydrogen Peroxide is H2O2, since Hydrogen Peroxide has two oxygen molecules that makes it a strong oxidizer. Hydrogen Peroxide kills bacteria by breaking down its cell wall. However, it is not necessarily good for humans. Hydrogen Peroxide is harsh on the epidermis and while it breaks down the cell walls of bacteria, it also destroys healthy skin cells due to oxidation. Rubbing alcohol is another effective disinfectant that is similar to alcohol-based hand sanitizers in the way that it kills bacteria.

            Now, we are still in the midst of the pandemic with the number of cases rising daily. So, keep your masks on, hands washed, and stay safe!

 

Sources:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5091001/

https://www.healthline.com/health/does-alcohol-kill-germs#can-it-kill-germs

www.ncbi.nlm.nih.gov/pmc/articles/PMC5264297/

www.cdc.gov/infectioncontrol/guidelines/disinfection/disinfection-methods/chemical.html 

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About The Author

Erin Kang is a senior at James S. Rickards High School and is a part of the Sciteens team. Her hobbies include baking, listening to music, and playing the violin. If you have any questions or future article recommendations, feel free to contact her at erin@sciteens.org.

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