Background: The effectiveness of hand rubbing with alcohol-based handrub (ABHR) is impacted by several factors. To investigate these, World Health Organization (WHO) commissioned a systematic review.

Aim: To evaluate the impact of ABHR volume, application time, rubbing friction and hand size on microbiological load reduction, hand surface coverage or drying time.

Methods: Medline, CINAHL, Web of Science and ScienceDirect databases were searched for healthcare or laboratory-based primary studies, published in English, (1980- February 2021), investigating the impact of ABHR volume, application time, rubbing friction or hand size on bacterial load reduction, hand coverage or drying time. Two reviewers independently performed data extraction and quality assessment. The results are presented narratively.

Findings: Twenty studies were included in the review. Categories included: ABHR volume, application time and rubbing friction. Sub-categories: bacterial load reduction, hand size, drying time or hand surface coverage. All used experimental or quasi-experimental designs. Findings showed as ABHR volume increased, bacterial load reduced, and drying times increased. Furthermore, one study showed that the application of sprayed ABHR without hand rubbing resulted in significantly lower bacterial load reduction than poured or sprayed ABHR with hand rubbing (- 0.70; 95%CI: - 1.13 to - 0.28). Evidence was heterogeneous in application time, volume, technique, and product. All studies were assessed as high risk of bias.

Conclusions: There is insufficient evidence to change WHO recommendation of a palmful of ABHR in a cupped hand applied for 20-30 s or manufacturer-recommended volume applied for about 20 s (Centers for Disease Control and Prevention). Future hand hygiene research should standardise volume, application time, and consider hand size.