Increasingly, healthcare facilities have opted for foam over liquid soap, but that move could put patients and healthcare workers at increased risk of infection, a small study published in the American Journal of Infection Control found.
"Foam soap was not as effective as liquid soap in eliminating hand bacterial load," the study concludes.
Two sets of healthy subjects washed their hands using the same method — wetting their hands, using one pump of soap, washing for 6 seconds and drying with paper towels for 4 seconds — but using either foam or liquid versions of the same brand of nonantimicrobial soap.
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Researchers then swabbed participants' hands and cultured the swabs to assess how much bacteria was left.
In the first set of subjects, "washing hands with the liquid soap led to a significant reduction in the mean hand bacteria load … whereas foam soap was ineffective," the study's authors wrote. "In repeat experiments, washing hands with foam soap had no influence on bacterial colony counts … whereas washing with liquid soap led to a significant decrease in bacterial load."
Ultimately, the researchers concluded foam soap may give people a false sense of security and could "potentially lead to the spread of resistant bacteria."
Because the sample size of the survey was small, the researchers recommended repeating the experiment with more subjects and in different settings.