How Hand Sanitizer Works & How to Use It

Now that hand sanitizer has transformed into liquid gold, it’s important to know how it works, what it’s good for, and how to use it.

First, let me undercut myself by saying that washing hands with soap and water is always the best option. Hand san, as I affectionately call it, is only for situations when soap and water is not available[i], and even using it, you should not consider your hands to be as clean as if you washed with soap and water.

Soap cleans hands or other surfaces by removing debris, including dirt, grease, chemicals, and germs. Hand sanitizers, on the other hand, deactivate many, but not all, bacteria and viruses, and do not remove anything.

Take a look at the back label of your closest hand sanitizer. Under “Use,” you’ll likely see words like “reduces” or “decreases” bacteria instead of words like “kills” or “cleans.” This is key to understanding what hand san is, and is not, capable of.

The most important part of a hand sanitizer is its active ingredient. This is the workhorse. The heavy lifter. The point in using it. Without a good active ingredient, at the right concentration, the whole product is useless.

There are several active ingredient options allowed for use in hand sanitizers by the FDA. Most common in the U.S. are ethyl alcohol, isopropyl alcohol, and benzalkonium chloride. Though it’s an FDA-allowed active ingredient, I’m not a fan of benzalkonium chloride. It may be less effective[ii] and is linked to antibiotic resistance[iii]. My focus here is on the alcohol-based hand sanitizers.

Ethyl alcohol is also called ethanol and is what you’ll find in cocktails. But don’t drink ethanol-based hand san – it’s too strong. And don’t make hand san with your favorite tequila – it’s not strong enough. (Save it for Happy Hour.)  

Isopropyl alcohol, also called isopropanol or rubbing alcohol, is what you’ll find at the pharmacy, usually at a concentration of 70% or 99%. There are quite a few other alcohols, including methanol, which I address below, but isopropyl alcohol and ethyl alcohol are the two that best combine safety and efficacy for hand sanitizing. 

How Alcohol-Based Hand Sanitizer Works

Alcohol-based hand sanitizers, at the right concentration, reduce the amount of certain bacteria[iv] and viruses[v] on your skin.

Bacteria, as living cellular organisms, are surrounded by a cell membrane made of lipids and proteins. (The word “lipid” derives from the Greek word for fat.) Viruses are not alive, but can be divided into two groups: enveloped and non-enveloped. Enveloped viruses are those that are surrounded – or enveloped – by a fatty lipid/protein layer. Common enveloped viruses are the virus that causes the common cold, influenza, and the coronavirus.

The cell membrane of bacteria and this envelope on certain viruses have something in common: they both contain lipids and proteins. This is what alcohol uses against them.

Alcohol is an amphiphilic molecule, which means one end is hydrophilic (water-loving) and the other is lipophilic (fat-loving). The lipophilic end of the alcohol molecules attaches to the lipids in the outer layers of bacteria and enveloped viruses, dissolving them and ripping the surface of the germ apart. Alcohol additionally pounces on the proteins in the membrane or envelope plus any that spill out from inside. Alcohol breaks down the structure of proteins in a process called denaturing. It’s one-two punch[vi] that is very satisfying to think about.

Woohoo! I want that in my corner! Except…

There are some common germs that alcohol doesn’t work against such as norovirus (the scourge of schools and cruise ships), cryptosporidium (a microscopic parasite), or Clostridium (a bacterial spore)[vii]. And remember, hand sanitizer does not remove any dirt, oils, or chemicals. Further, when hands are too soiled with dirt or grime, the hand sanitizer probably cannot even reach the target germs[viii].

This is what makes soap and water the better option.

How to Use Hand Sanitizer Effectively

The CDC, FDA, and Mayo Clinic agree on the best way to use hand sanitizer to maximize efficacy:

• Coat surfaces of your hands[ix] with the wet sanitizer. Include your palms, back of hands, and fingertips.
• Rub your hands thoroughly until hand sanitizer is dry.
• Do not wipe off wet hand sanitizer. It needs to stay on hands until it evaporates to do its job. Keep rubbing your hands until dry.

Three Common Mistakes When Using Hand Sanitizer

• Using too little
• Rubbing too short a time
• Wiping it off before dry

I get it. Hand sanitizer has been hard to find, so you want to conserve it when you have it. However, trying to conserve it by using a small amount is pointless. Using too little hand sanitizer doesn’t work. You may feel like your hands are cleaner, but that is a false sense of security.

Why 60% and Not 100%

As the FDA says, “If soap and water are not available, CDC recommends consumers use an alcohol-based hand sanitizer that contains at least 60% alcohol.” It begs the question, though, if 60% alcohol is good, wouldn’t 100% be better?

Alcohol at too high a concentration poses a couple of problems. First, the alcohol evaporates too quickly off the skin, before it can reach its full germ-killing potential. The diluting water content keeps the alcohol on the hands longer, allowing it to work against the germs longer.

Secondly, alcohol is very drying, and the higher the concentration, the more drying it is. 100% alcohol, used regularly would be so drying as to damage the skin, causing it to crack and bleed and making it more vulnerable to infections. This defeats the ultimate purpose of keeping you healthy.

On the other end of the spectrum, hand sanitizers with alcohol concentrations below 60% are too diluted to address all the potential germs.

During the initial hand sanitizer shortage, there was a surge in DIY hand sanitizer recipes blazing up the Internet. These used various beverage alcohols such as vodka. However, most drinking alcohols contain an alcohol content less than 40% and therefore would not make effective hand sanitizers. Put them to use in your favorite cocktail instead.

The Problems with Making Your Own

While the FDA has given temporary authorization to pharmacies and alcohol manufacturers to produce alcohol-based hand sanitizers, the FDA does not recommend individuals make their own. Their concern is either that individuals will inadvertently make an overly-diluted, ineffective product that gives a false sense of security, or that home-made formulations could cause burns or other harm.

What’s with Methanol and the FDA List of Hand Sanitizers Not to Use?

Methanol, aka methyl alcohol or wood alcohol, is used in the creation of fuels, solvents, and pesticides. It is poisonous to humans but has been showing up in hand sanitizer products that claim to contain ethanol. Numerous people have been hospitalized and have died because of this. The hazards of methanol to humans are significant and well-known. Symptoms are wide ranging, from loss of vision to loss of consciousness and death, and may not be immediately apparent.

Methanol won’t be listed on a label. To avoid it, refer to the FDA’s list of toxic hand sanitizers, which currently stands at 115 products, and further avoid other products made by those manufacturers, just in case. The best bet is to buy from trusted brands. And never ingest hand sanitizer.

Also, on this list are a few hand sanitizers found to have insufficient alcohol concentrations, which leads to reduced effectiveness and a false sense of security.  

Why Does a Lot of New-to-Market Hand Sanitizer Smell So Bad?

It seems like everyone is getting into the hand sanitizer business these days. Anyone with the means to produce alcohol – from industrial plants to perfumeries to breweries – have made their way onto the bandwagon. It’s an impossibly easy market to jump into at the moment. Furthermore, demand for hand sanitizer is so high[x], that consumers may be taking what they can find, with less regard for quality, sourcing, packaging, ethics, price, or even smell.

One FDA requirement is that the alcohol in hand sanitizer be denatured. This is a different definition of “denature” from what I mentioned above regarding proteins. This means something must be added to the alcohol that makes it so unpalatable no one will be tempted to drink it. It’s a safety consideration because consuming 60%+ alcohol would quickly lead to alcohol poisoning.

Usually this means manufacturers use denaturing agents that make the product smell good but taste bad, such as with certain essential oils or bittering agents. However, now, some manufacturers are throwing all manner of cheap junk into the hand sanitizer to meet this denaturing requirement. These agents not only taste bad but smell worse. They certainly make not touching your face all the easier.

How to Buy Good Hand Sanitizer

• Read ingredients. For so many reasons, read ingredients. Look for an active ingredient of ethyl alcohol over 60% or isopropyl alcohol over 70%.
• Avoid “alcohol-free.” The term may sound like a benefit, but it could indicate that the active ingredient is benzalkonium chloride, which as stated above, is less effective than alcohol.
• Check the FDA List of toxic hand sanitizers. Avoid mentioned products and their manufacturers.
• Don’t believe outrageous claims. If it sounds too good to be true, it probably is.
• Ignore “FDA-approved.” This is a marketing gimmick. Outside of pandemic times, all hand sanitizers must be registered with the FDA and are considered over-the-counter (OTC) drugs. However, the FDA does not authorize the use of the statement “FDA approved.” This term is used by a manufacturer in order to make their product seem more authorized than another.

Best Hand Hygiene

The best way to keep your hands clean is by a good washing with soap and water. Should I say it again?

I learned a ton in researching this article. Whew! Makes up for not taking Microbiology or Organic Chemistry in college! Maybe not quite. To give your brain a workout, read through the research I’ve cited. Even as a lay person, I learned a lot about chemistry, biology, and the world around me, and how best to interact with it.

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[i] FDA. “FDA issues final rule on safety and effectiveness of consumer hand sanitizers,” https://www.fda.gov/news-events/press-announcements/fda-issues-final-rule-safety-and-effectiveness-consumer-hand-sanitizers.

[ii] Alberto Berardi, et al. 2020. “Hand sanitisers amid CoViD-19: A critical review of alcohol-based products on the market and formulation approaches to respond to increasing demand.” International Journal of Pharmaceutics, Volume 584, 119431, ISSN 0378-5173, https://doi.org/10.1016/j.ijpharm.2020.119431.

[iii] Kampf, Günter, 2018. “Biocidal Agents Used for Disinfection Can Enhance Antibiotic Resistance in Gram-Negative Species.” Antibiotics 7, no. 4: 110, https://www.mdpi.com/2079-6382/7/4/110/htm.

[iv] Kampf G, Hollingsworth A. “Comprehensive bactericidal activity of an ethanol-based hand gel in 15 seconds.” Ann Clin Microbiol Antimicrob. 2008;7:2. Published 2008 Jan 22, https://ann-clinmicrob.biomedcentral.com/articles/10.1186/1476-0711-7-2.

[v] G. Kampf, “Efficacy of ethanol against viruses in hand disinfection, Journal of Hospital Infection,” Volume 98, Issue 4, 2018, Pages 331-338, ISSN 0195-6701, https://doi.org/10.1016/j.jhin.2017.08.025.

[vi] McDonnell G, Russell AD. Antiseptics and disinfectants: activity, action, and resistance [published correction appears in Clin Microbiol Rev 2001 Jan;14(1):227]. Clin Microbiol Rev. 1999;12(1):147-179, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC88911/.

[vii] Gold NA, Mirza TM, Avva U. Alcohol Sanitizer. [Updated 2020 Jun 24]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan, https://www.ncbi.nlm.nih.gov/books/NBK513254/.

[viii] Todd EC, et al. “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. Journal of Food Protection. 2010;73(11):2128-2140, https://doi.org/10.4315/0362-028X-73.11.2128.

[ix] CDC. “Show Me the Science – When & How to Use Hand Sanitizer in Community Settings,” https://www.cdc.gov/handwashing/show-me-the-science-hand-sanitizer.html.

[x] Alberto Berardi, et al. “Hand sanitizers amid CoViD-19: A critical review of alcohol-based products on the market and formulation approaches to respond to increasing demand,” International Journal of Pharmaceutics, Volume 584, 2020, 119431, ISSN 0378-5173, https://doi.org/10.1016/j.ijpharm.2020.119431.

Further reading

• My Hand Sanitizer – Armed and Ready
• Traveling with Hand Sanitizer
• Handwashing How-To and How-Not-To