Efficacy of ethanol-based hand foams using a clinically relevant amount of foam: a cross-over controlled study among healthy volunteers

Background: Foams based on 62% ethanol are offered for hand decontamination in some countries. A long time for drying may reduce the compliance of healthcare workers to apply the recommended amount of foam.

Objective: We have investigated their drying times and efficacy.

Methods: Four foams all based on 62 % ethanol which are common in US hospitals (Alcare plus, Avagard Foam, Bode test foam, Purell Instant Hand Sanitizer) were applied in a total of 7 variations to 14 volunteers. The drying time was measured. The efficacy of 1.6 g of two foams which are quite commonly used in the US was compared according to EN 1500 to 2 x 3 mL of 2-propanol 60% (v/v) and to 1.6 g of water on hands artificially contaminated with Escherichia coli using a cross-over design with 15 volunteers.

Results: The mean weight of applied foam varied between 1.78 and 3.09 g, the mean duration to dry was between 37 s and 103 s. The correlation between the applied amount of foam and the time until hands felt dry was highly significant (p < 0.001; Pearsons correlation coefficient: 0.724; 95% confidence interval: 0.52 – 0.93). Based on the linear correlation, an amount of 1.6 g is an intercept of a 30 s application time. Application of 1.6 g of one foam coded as A (mean log₁₀-reduction: 3.05 ± 0.45) and another foam coded as B (3.58 ± 0.71) was significantly less effective in comparison to the reference disinfection (4.83 ± 0.89 and 4.60 ± 0.59, respectively; p < 0.001). Application of 1.6 g of water revealed a mean log₁₀-reduction of 2.39 ± 0.57.

Conclusions: When using foams based on 62% ethanol the time required for dryness quite often exceeds the recommended 30 s. It is therefore likely that only a small volume of such a foam will be applied in clinical practice. Such a small amount, however, failed to meet the efficacy requirements of EN 1500 and was only somewhat more effective than water.