Skin Microbiome Diversity Lower With Soap and Water Compared With Hand Sanitizer Use

While skin microbiome diversity had no before and after difference with alcohol-based hand sanitizer use, a recent study¹ found that microbiome diversity was lower after handwashing with soap and water.

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In the study, researchers Vindenes et al sought to determine the immediate impact of hand hygiene, such as traditional handwashing and use of alcohol-based hand sanitizers, on the profiling and sampling of bacterial skin microbiota. They based the study around the increased use of hand hygiene measures during the COVID-19 pandemic as a basis for the study.

Participants included 5 female participants between the ages of 36 and 55 years old. All 5 participants were considered healthy and did not have any skin lesions present on their hands at the time of skin sampling. None had used antibiotics during the month leading up to sampling.

The process of skin sampling was carried out between 2 days. On each day, participants were instructed to refrain from showering or use of soaps, creams, or cosmetics.

On day 1 of the study, researchers collected skin microbiota samples before and 15-minutes after use of alcohol-based hand sanitizer. On day 2 of the study, researchers collected samples before and 15-minutes after traditional handwashing with mild faucet water and extra mild liquid soap.

Samples were collected from the dorsal hand surface and from the skin of the inner elbow due to lack of environmental exposure and the site’s potential for moisture. Sampling sites were rubbed in a back and forth motion a total of 25 times using a collection swab moistened in sterile solution.

Researchers then conducted DNA extraction and bioinformatic sequence processing.

After use of alcohol-basedhand sanitizers on day 1, researchers found that there was an increase in genera Streptococcus, Propionbacterium, and Corynebacterium, while there was a decrease in Actinobacteria, Micrococcus, and Sediminibacterium. On the dorsal hand, levels of Streptococcus, Staphylococcus, Micrococcus, and Lactobacillus remained relatively unchanged before and after use.

On day 2, following the use of traditional handwashing with soap and water, researchers noted a more pronounced change in the skin’s microbiota composition. After handwashing, there was an increase in the presence of genera Sediminibacterium and Sphingomonas, while there was a decrease in genera Lactobacillus, Neisseriaceae, Propionibacterium, Staphylococcus, and Streptococcus.

Furthermore, there was no statistically significant difference in either day 1 or day 2 regarding alpha diversity. However, beta diversity underwent a drastic change before and after handwashing with soap and water on day 2.

“Our findings of an altered skin microbiota after hand washing with soap, but not after application of ABHS (alcohol-based hand sanitizer) is perhaps due to mechanical removal of bacteria during hand washing and the action of the surfactant found in soap,” according to Vindenes et al. “Our findings demonstrate that ABHS applied before sampling of the skin has negligible effect on DNA-based profiling of skin microbiota. Hand washing with soap and water will however have an impact and should be taken into consideration when comparing findings to studies performed in the pre-pandemic era.”

Reference

1. Vindenes HK, Drengenes C, Amin H, Bertelsen RJ. The impact of alcohol‐based hand Sanitiser and hand washing with soap and water on bacterial skin microbiota composition. JEADV Clin Prac. Published online 2023. doi:10.1002/jvc2.214