Evaluating the antimicrobial efficacy of long-lasting hand sanitizers on skin

The microbicidal efficacy of hand sanitizer formulations is usually measured through standardized quantitative suspension tests and fingerpad tests; these cannot evaluate long-lasting formulations or are impractical due to biological risks, high cost, or time required for testing. With increased numbers of long-lasting microbicidal activity claims of commercially available hand sanitizers, alternative testing strategies are required.

To explore the use of a standardized ex-vivo pig skin model to reproducibly measure long-lasting efficacy of an alcohol-free hand sanitizer formulation.

The microbicidal efficacy of an alcohol-free hand sanitizer was tested against Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae, and the enveloped virus SARS-CoV-2 with quantitative suspension tests (EN13727 and EN14476) with a contact time of 5 min. The product was then tested over a 6 h period using an ex-vivo pig skin model with a modified version of PAS 2424 to simulate the impact of skin abrasion.

Quantitative suspension tests yielded a >5 log₁₀ reduction for all organisms tested within a 5 min contact time. Pig skin tests showed reduced but consistent efficacy at all time points and indicated no significant impact of abrasion on efficacy.

The use of the ex-vivo pig skin model provides a potentially viable and convenient model system to test long-lasting hand sanitizer formulations, providing a path for sustainable hand sanitizer formulation claims of activity on skin.