By John Lovett
University of Arkansas System Division of Agriculture
Arkansas Agricultural Experiment Station
Hand sanitizers became ubiquitous during the COVID-19 pandemic, but scientists are still finding answers to questions about their efficacy.
While hand sanitizers are considered a reliable alternative to soap and water when hands are not visibly dirty or greasy, the application time of hand sanitizer remained a question, according to a recently published study from researchers with the Arkansas Center for Food Safety, a part of the University of Arkansas System Division of Agriculture’s research arm, the Arkansas Agricultural Experiment Station.
Francis Torko, a Ph.D. student and research assistant in the food science department, worked with Kristen Gibson, a professor of food safety and microbiology and director of the center, to put five commercially available foam hand sanitizers to the test. They found that application time made a big difference.
In their evaluation of hand sanitizers with 30 volunteers, tests revealed that those who rubbed their hands with sanitizer until it was dry saw a greater reduction of viruses than those who rubbed their hands for the typical 10 seconds.
Four of the hand sanitizers were alcohol-based, and one had benzalkonium chloride as its active ingredient. Surrogate viruses representing those that cause respiratory and gastrointestinal illnesses were applied on the palm area of the volunteers’ hands before the hand sanitizer was used.
The study also supported other research that found product formulation, rather than just active ingredient concentration, impacted product efficacy.
“The study simulated real-world conditions and provides valuable evidence to inform future hand sanitizer practices aimed at maximizing the reduction of infectious viral pathogens on the hands,” said Gibson, who is also the Donald “Buddy” Wray Endowed Chair in Food Safety for the experiment station and the Dale Bumpers College of Agricultural, Food and Life Sciences.
The study, titled Product formulation and rubbing time impact the inactivation of enveloped and non-enveloped virus surrogates by foam-based hand sanitizers,” was published in the journal Applied and Environmental Microbiology in March.
Torko also presented the results of the study at the 2025 International Association for Food Protection conference in Cleveland.
Filling the gaps
Differences between this study and past research on hand sanitizers include the use of commercially available hand sanitizers, rather than lab-based solutions, and evaluation of the whole palm area of the hand, rather than just the fingers.
The Center for Food Safety study also used direct comparisons between different rubbing times and the volume of sanitizer applied to hands for “enveloped” and “non-enveloped” viruses. Examples of enveloped viruses include those that cause respiratory diseases like influenza and coronaviruses. Non-enveloped viruses include human noroviruses that cause gastrointestinal illnesses.
Enveloped and non-enveloped viruses can potentially be transmitted by contaminated surfaces, according to Gibson.
In environments with high contact rates, such as childcare centers, food establishments, public transport, and gyms, contaminated surfaces and hands play a critical role in pathogen transmission, Torko noted, because hands often make primary contact with pathogen points of entry such as the eyes, mouth and nose.
Formulation factor
The U.S. Centers for Disease Control recommends that alcohol-based hand sanitizers contain a minimum of 60 percent alcohol, whereas the World Health Organization recommends 80 percent ethanol or 75 percent isopropanol.
Although most previous studies on hand sanitizer efficacy noted the concentration of active ingredients as a key factor, Torko said the results of their study and other recent publications suggest that the efficacy of hand sanitizers may not solely depend on the concentration of active ingredients but rather on the overall formulation of the product.
For example, studies cited by Torko and Gibson showed there were significant differences between products with similar active ingredient concentrations, as well as a lack of significant differences between products with varying active ingredient concentrations. Two other studies they cited observed that reducing glycerol in hand sanitizers appeared to positively impact the efficacy of the formulations. Glycerol is added to moisturize skin and to slow the evaporation of alcohol, Gibson said.
Results of the Center for Food Safety study showed, for example, that a 63 percent isopropanol demonstrated a higher log reduction than a 70 percent isopropanol product that was formulated differently. These results emphasize that overall product formulation impacts efficacy, not just concentration of active ingredients.
Members of the Arkansas Center for Food Safety seek evidence-based solutions to food safety issues within Arkansas and beyond through research, innovation and collaboration between the public and private sectors. In addition to food safety issues in vegetables and meats, the center also focuses on novel processing technologies, mitigating mycotoxins in grains, and low-moisture food safety challenges.
The hand sanitizer study was supported by Agriculture and Food Research Initiative Competitive Grant No. 2020-67017-32427 from the United States Department of Agriculture National Institute of Food and Agriculture.
To learn more about the Division of Agriculture research, visit the Arkansas Agricultural Experiment Station website. Follow us on X at @ArkAgResearch, subscribe to the Food, Farms and Forests podcast and sign up for our monthly newsletter, the Arkansas Agricultural Research Report. To learn more about the Division of Agriculture, visit uada.edu. Follow us on X at @AgInArk. To learn about extension programs in Arkansas, contact your local Cooperative Extension Service agent or visit uaex.uada.edu.
