How Hand Sanitizer Works

Hand sanitizer has come to the forefront as one of the tools to help reduce the spread of COVID-19. Which is the best type to use and how does hand sanitizer work? The Centers for Disease Control and Prevention (CDC) advise that using a hand sanitizer containing at least 60% alcohol can help you avoid spreading germs to others and getting sick.¹ 

Hand washing vs. hand sanitizer

If you need to clean your hands, you should opt to use a hand sanitizer if there is no soap and water available and you have no visible grease/dirt on your hands. Research has identified that hand sanitizers do not work well if hands are visibly dirty.^1 2 3

However, if soap and water are available, washing hands is the best way to reduce the amount of germs and chemicals on the hands.¹ The CDC and U.S. Food and Drug Administration (FDA) advises that you should wash your hands with soap and water for at least 20 seconds, especially after going to the bathroom, before eating, and after coughing/sneezing, to have the best effect against spreading germs.^{1 4}

What is hand sanitizer made from?

The main ingredient of most hand sanitizers is alcohol. To ensure hand sanitizers are produced safely and are effective, the FDA ruled that they must contain one of three active ingredients; ethyl alcohol (ethanol), isopropyl alcohol (isopropanol), or benzalkonium chloride.⁵ Ethyl alcohol (a primary alcohol) and isopropyl (a secondary alcohol) are closely related but have different properties and absorbency levels. Ethanol is chemically the same as alcohol that you drink, whereas isopropyl is more commonly known as rubbing alcohol.

Using a hand sanitizer with at least 60% alcohol (ethanol and isopropyl alcohol are most commonly used as the active ingredient) is recommended by the CDC for maximum effect. In fact, studies show that the best, broad, antimicrobial efficacy is achieved with 60-85% ethanol, 60-80% isopropanol, and 60-80% n-propanol. However, higher ethanol concentrations can be even more effective.⁶ Ethanol seems to be the most effective alcohol against viruses. However, propanol is considered to be better at killing bacteria.⁷

How does hand sanitizer work?

Alcohol-based hand sanitizers are proven to be very effective at destroying various pathogens (disease-causing agents).⁷ Ethanol is well known to be antimicrobial and has been used to disinfect the hands since 1888.⁶ 

The process by which alcohol kills germs is called denaturation. Alcohol molecules have both water and fat-loving properties. The alcohol molecules in hand sanitizer work by bonding and breaking down the protective fat membrane around a virus or bacteria cell. When this membrane is broken down, the inside of the cell containing all its critical components is exposed. It then dissolves, ceases to function, and dies. 

However, hand sanitizer does not kill all germs. The CDC advises that hand sanitizer is not as effective at killing certain kinds of germs, like Cryptosporidium, Norovirus, or Clostridium difficile, as using soap and water is.¹It also doesn’t remove harmful chemicals like pesticides or heavy metals.¹ Therefore, soap and water is still the best option to clean your hands where available. 

Is hand sanitizer bad for you?

It is important to remember that hand sanitizer can be dangerous to small children if ingested. The U.S. poison control centers received nearly 85,000 calls about children ingesting hand sanitizer between 2011 – 2015.¹ If a child drinks even a small amount of hand sanitizer, it can cause alcohol poisoning. Therefore, the FDA advises that children aged six and under are supervised when using hand sanitizer.⁴

There’s no evidence to suggest that hand sanitizers are harmful; however, if you use hand sanitizer very frequently, it can cause skin irritation. In rarer cases, reactions like swelling, redness, burning sensations, and tingling can occur. If you react to hand sanitizer, then seek help and advice from your doctor.⁷

Some people are worried that using a hand sanitizer regularly can cause antibiotic resistance. However, this is not the case. Both alcohol-based hand sanitizers and washing hands with soap and water do not contribute to antibiotic resistance.⁸

The dos and don’ts of using hand sanitizer

Technique matters when it comes to getting the best results from using hand sanitizer. Follow these steps for the most effective results:

• Ensure your hands are free of dirt or grease before using a hand sanitizer.
• Apply the hand sanitizer to the palm of one hand (using the amount stipulated on the product label).
• Rub your hands together.
• Rub the hand sanitizer over all the surfaces of your hands and fingers until your hands are dry. 
• The process of using a hand sanitizer should take approximately 20 seconds.

The bottom line

Washing hands with soap and water is still the most effective way to remove the majority of germs and chemicals. Hand sanitizers can be used when soap and water are not available but be aware that they do not get rid of all types of germs. If your hands are dirty or greasy, then hand sanitizers are not as effective. When using a hand sanitizer, try to use one that contains at least 60% alcohol (which should be stated on the product label). 

References:

1. Show Me the Science – When & How to Use Hand Sanitizer in Community Settings | Handwashing | CDC. Cdc.gov. https://www.cdc.gov/handwashing/show-me-the-science-hand-sanitizer.html. Published 2021. Accessed February 5, 2021.
2. CHARBONNEAU D, PONTE J, KOCHANOWSKI B. A Method of Assessing the Efficacy of Hand Sanitizers: Use of Real Soil Encountered in the Food Service Industry. J Food Prot. 2000;63(4):495-501. doi:10.4315/0362-028x-63.4.495
3. TODD E, MICHAELS B, HOLAH J, SMITH D, GREIG J, BARTLESON C. Outbreaks Where Food Workers Have Been Implicated in the Spread of Foodborne Disease. Part 10. Alcohol-Based Antiseptics for Hand Disinfection and a Comparison of Their Effectiveness with Soaps. J Food Prot. 2010;73(11):2128-2140. doi:10.4315/0362-028x-73.11.2128
4. Q.A.s Hand sanitizer and COVID-19. U.S. Food and Drug Administration. https://www.fda.gov/drugs/information-drug-class/qa-consumers-hand-sanitizers-and-covid-19. Published 2021. Accessed February 5, 2021.
5. FDA issues final rule on safety and effectiveness of consumer hand sanitizers. U.S. Food and Drug Administration. https://www.fda.gov/news-events/press-announcements/fda-issues-final-rule-safety-and-effectiveness-consumer-hand-sanitizers. Published 2021. Accessed February 8, 2021.
6. Kampf G, Kramer A. Epidemiologic background of hand hygiene and evaluation of the most important agents for scrubs and rubs. Clin Microbiol Rev. 2004;17(4):863-893. doi:10.1128/CMR.17.4.863-893.2004
7. Gold NA, Mirza TM, Avva U. Alcohol Sanitizer. [Updated 2020 Jun 24]. In: StatPearls [Internet]. Treasure Island (F.L.): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK513254/
8. Frequent Questions About Hand Hygiene | Handwashing | CDC. Cdc.gov. https://www.cdc.gov/handwashing/faqs.html. Published 2021. Accessed February 8, 2021.