Rub Hand Sanitizer Until Dry for Maximum Effectiveness

The Problem

Hand sanitizers became a global staple during the COVID-19 pandemic, but questions remained about their real-world performance. While health agencies such as the United States Centers for Disease Control and Prevention and the World Health Organization set minimum alcohol content guidelines, the optimal rubbing time and the influence of formulation differences are not well defined. Improper use of hand sanitizers risks potentially leaving harmful viruses on their hands and increasing the risk of disease transmission in high-contact environments.

The Work

To close these knowledge gaps, food science Ph.D. student Francis Torko, a research assistant in the Department of Food Science, collaborated with adviser Kristen Gibsson, Professor of Food Safety and Microbiology and Director of the Arkansas Center for Food Safety with the Arkansas Agricultural Experiment Station. Thirty volunteers participated in controlled tests using five commercially available hand sanitizers. Four of the hand sanitizers were alcohol-based, and one had benzalkonium chloride as its active ingredient. Harmless surrogates for different kinds of viruses, like influenza and human noroviruses, were applied to the palm area of volunteers’ hands. The study then measured the viral reduction achieved when participants rubbed their hands for 10 seconds compared to when they rubbed until the sanitizer was dry.

The Results

A significant increase in viral reduction was seen when participants rubbed their hands until the sanitizer fully dried compared to the typical 10-second rub. The researchers also found that formulation mattered more than active ingredient concentration, reinforcing evidence that glycerol content and formulation additives influence sanitizer performance by altering alcohol evaporation and skin contact time. For example, one of the sanitizers tested had 63% isopropanol but achieved higher viral reduction than a 70% isopropanol product with a different formulation.

The Value

The study’s real-world approach of testing commercially available products on the full palm rather than just fingers offers valuable context for future hand sanitizer usage recommendations. The findings also offer practical implications for consumers, healthcare providers, and public health officials. Extending hand sanitizer rub time until the product dries can significantly improve sanitizer effectiveness. Additionally, the research highlights the need to consider product formulation, not just active ingredient content, when evaluating sanitizer efficacy.

About the Researchers