Sanitizer or Soap? The Studies Settle It (Mostly)
The study: Aiello AE, Coulborn RM, Perez V, Larson EL. 2008. “Effect of Hand Hygiene on Infectious Disease Risk in the Community Setting: A Meta-Analysis.” American Journal of Public Health 98(8):1372–1381. DOI 10.2105/AJPH.2007.124610. Thirty hand-hygiene trials from 1960–2007 were pooled: improved hand hygiene cut gastrointestinal illness by 31% (95% CI 19–42%) and respiratory illness by 21% (5–34%). The most beneficial intervention was hand-hygiene education with plain, nonantibacterial soap — and antibacterial soap showed little added benefit over it.
The hand hygiene debate generates strong opinions, so start with the pooled data. Across thirty trials, the intervention that worked best was not a stronger chemical — it was education plus ordinary soap. Antibacterial soap, the product that promised more, delivered essentially nothing extra. That finding sets the tone for the sanitizer-versus-handwashing question: the evidence keeps favoring the simple, well-executed basics over the upgraded chemistry.
What the comparison shows
Against most vegetative bacteria, alcohol-based sanitizers perform well on clean hands — often matching handwashing in log-reduction terms. The qualifier does enormous work. Sanitizers are inactivated by organic matter and do not remove soil, grease, or food residue; on dirty, greasy food-handling hands, their efficacy drops sharply, because the alcohol is consumed by the very soil it sits in. A sanitizer applied to a visibly dirty hand is mostly being wasted on the dirt. Handwashing physically removes contamination — the soap lifts, the water carries away — which is why technique and duration matter (the 20-second rule has data behind it: time under friction is what dislodges microbes from skin crevices) and why sanitizer performance hinges on coverage, volume, and contact time. A quick squirt that misses the thumbs and fingertips is a different intervention than the one the laboratory validated.
Against norovirus, the gap is decisive. Alcohol sanitizers are substantially weaker against norovirus than soap-and-water washing, which physically removes the virus rather than trying to inactivate it. Given norovirus’s dominance in foodborne outbreaks and its food-handler transmission route, this single fact settles the debate for food operations. Sanitizers have their place — healthcare settings, field work without water — but in food handling they are a supplement to handwashing, never a substitute.
The policy the data supports
Food codes have the hierarchy right: handwashing with soap and water is the requirement; sanitizers may be used additionally, not instead. In practice: wash after handling raw foods, after using the restroom, after touching garbage, after handling money or cleaning chemicals — the dirty-hands situations where sanitizer underperforms. Sanitizer has a legitimate role for in-between moments on relatively clean hands, and in some operations as a second step after washing, where it adds a margin on top of an already-clean hand rather than being asked to do the cleaning itself — a finishing touch, not the main event.
The Aiello meta-analysis adds the deeper lesson: education was part of the winning intervention. Technique — how people actually wash — varies enormously, and the programs that teach and verify it get the illness reductions the pooled data promise. Operations that have quietly let sanitizer dispensers replace sinks in practice, if not on paper, have the hierarchy backwards. The evidence-based hand hygiene program is unglamorous: accessible sinks with soap and single-use towels, washing enforced at the required times, technique taught and verified rather than assumed, sanitizer available as a supplement where appropriate. Thirty trials agree — when the comparison is done properly, against the illnesses that matter, soap and water win, and the fanciest dispenser on the wall cannot change that verdict.
Source: Aiello AE, Coulborn RM, Perez V, Larson EL. 2008. Effect of hand hygiene on infectious disease risk in the community setting: a meta-analysis. American Journal of Public Health 98(8):1372–1381.