Hand decontamination: influence of common variables on hand-washing efficiency

This study has evaluated the effects of wash time, friction and soap on the decontamination of hands seeded with Escherichia coli. In one protocol contaminated hands were held passively under running tap water. In another, contaminated hands were again held under running tap water and the fingers and palms rubbed together. In the final protocol soap and friction were used under running water. The number of contaminant E. coli transferred by touch contact to food or a surrogate item representing skin was quantified, before washing and after washing for intervals up to 20 s. Decontamination profiles were determined for each protocol. When hands were washed under running water with friction over a period of 20 s, the number of E. coli contaminating food and the skin surrogate was progressively reduced respectively to 0.18% and 0.34% of the baseline level. Running water alone was comparatively ineffective. The addition of soap showed a modest benefit. We conclude that in situations where hands are not visibly soiled, a purposeful hand wash under running water for 20 s, with friction, will deliver an effective outcome that can be improved marginally by the addition of soap.