The concept that soap carries and transfers bacteria between users is one of the most persistent myths in personal hygiene. It surfaces regularly as a reason to prefer liquid hand soap and body wash over bar soap. The evidence tells a different story.
What Research Actually Shows
The definitive study on this question was conducted in 1988 by Heinze and Yackovich, published in Epidemiology and Infection. The researchers inoculated bar soap bars with E. coli and Pseudomonas aeruginosa at concentrations 70 times higher than normally found on contaminated soap. They then had subjects wash their hands with these heavily inoculated bars. Result: no transfer of bacteria to subjects' hands was detected.
Subsequent studies have confirmed this finding. Despite bar soap being in direct contact with skin during washing — and potentially harboring bacteria on its surface between uses — the washing process itself does not transfer those bacteria to the user. The mechanics of washing — the lather, the rinsing, the physical removal of surface material — prevent transfer rather than facilitate it.
Why Bar Soap Doesn't Transfer Bacteria
Several mechanisms explain why bar soap doesn't effectively transfer bacteria despite potentially carrying them on its surface:
pH of soap surface. Bar soap is alkaline — pH 9 to 10. Most pathogenic bacteria prefer near-neutral pH environments (6.5 to 7.5). The alkaline environment of soap surface is inhospitable to most pathogens, limiting their viability even before the washing process.
The lathering action. Lathering with soap is a mechanical process that generates shear forces in the water film between hands and soap bar. These forces prevent effective transfer of surface bacteria to the washing person's skin even when bacteria are present on the bar.
Rinsing removes surface material. Any bacteria that might transfer in the initial lathering phase are removed by the rinsing that follows. The soap's surfactant action that lifts bacteria from the user's skin during washing also means any soap surface bacteria present during lathering are removed by the same rinse.
When Soap Surface Does Accumulate Bacteria
While soap doesn't transfer bacteria during use, bars stored in standing water do accumulate surface bacteria between uses. This is a hygiene concern for high-traffic shared soap — public restrooms, gym showers — where many different people are using the same bar without adequate drying time between uses.
For personal use, proper storage (drainage dish, air drying between uses) prevents significant bacterial accumulation. The bar you use alone in your home shower, stored properly, is microbiologically safe.
What This Means Practically
The bar soap vs liquid soap hygiene debate is settled by evidence: for personal use with adequate storage, bar soap is as hygienic as liquid soap. The liquid soap preference driven by bacterial transfer concerns is a marketing construct that succeeded by leveraging an intuitive concern that the research doesn't support.
Our natural bar soap lineup is designed for personal use with proper storage. Our Rust-Proof Corner Shower Caddy provides the drainage storage that keeps bars dry between uses and eliminates the surface bacterial accumulation that is the only legitimate hygiene concern about bar soap use.
Beyond Clean, Beyond Ordinary.