Product formulation and rubbing time impact the inactivation of enveloped and non-enveloped virus surrogates by foam-based hand sanitizers

Effective hand hygiene, such as hand washing and hand sanitizer use, is crucial in reducing infectious disease transmission via the hands. The efficacy of hand washing has been well-documented; however, relatively less is known regarding foam-based hand sanitizer efficacy, which is considered an effective alternative to washing hands with soap and water. Hand sanitizers are recommended by both the United States Centers for Disease Control and Prevention and the World Health Organization when the hands are not visibly dirty or greasy. This study examined the efficacy of five commercially available foam hand sanitizers-four alcohol-based and one non-alcohol-based-against enveloped and non-enveloped viruses using bacteriophage phi6 (Φ6) and bacteriophage MS2 as surrogates, respectively. A cocktail of MS2 and Φ6 (8 log PFU/mL) was inoculated on the hands and exposed to 3 or 6 mL of hand sanitizer product followed by rubbing the palmar surface of the hands together for 10 s or until dry. The results showed significant log reduction among the virus surrogates (<i>P</i> ≤ 0.05), with Φ6 consistently showing higher susceptibility across all factors compared with MS2 with log reductions of 2.83 ± 1.98 and 0.50 ± 0.53 log reduction, respectively. Although dosing volume did not significantly impact log reduction (<i>P</i> = 0.31), rubbing time significantly affected bacteriophage inactivation (<i>P</i> ≤ 0.05). Higher log reduction was observed when hands were rubbed until dry (2.69 ± 2.06), compared with the typical 10 s rubbing time (0.65 ± 0.75). This study revealed that the efficacy of commercially available foam hand sanitizers depends on rubbing time and overall product formulation, rather than exclusively on active ingredient concentration.IMPORTANCEHuman hands are a key factor in the transmission of viral diseases, and proper hand hygiene is regarded as the gold standard against the spread of such diseases. This study examined the effectiveness of a hand hygiene technique, that is, the application of foam-based hand sanitizers, against the inactivation of enveloped and non-enveloped virus surrogates on the hands. Factors such as virus type, rubbing time, volume of product used, and product formulation can significantly influence the efficacy of hand sanitizers. To assess these effects, we tested different rubbing times and product volumes across alcohol- and non-alcohol-based, foam hand sanitizer formulations, each with varying active ingredient concentrations and inactive ingredients. The study was performed on the palmar surface of human hands to realistically simulate real-world conditions, providing valuable evidence to inform future hand sanitizer practices aimed at maximizing the reduction of infectious viral pathogens on the hands.