Use of Plain Soap

Bannan EA, Judge LF. Bacteriological studies relating to handwashing: 1. the inability of soap bars to transmit bacteria. Am J Public Health 1965;55:915­21:

A study is reported to determine whether bar soaps, without
antibacterial additives, spread bacteria. The results reveal that
bacteria are not transferred by this means from person to person, nor
does the soap support bacterial growth.


Morbidity and Mortality Weekly Report, Recommendations and Reports October 25, 2002 / Vol. 51 / No. RR-16 Guideline for Hand Hygiene in Health-Care Settings, Recommendations of the Healthcare Infection Control Practices, Advisory Committee and the HICPAC/SHEA/APIC/IDSA Hand Hygiene Task Force:

Plain (Non-Antimicrobial) Soap
   Soaps are detergent-based products that contain esterified
fatty acids and sodium or potassium hydroxide. They are avail-
able in various forms including bar soap, tissue, leaflet, and
liquid preparations. Their cleaning activity can be attributed
to their detergent properties, which result in removal of dirt,
soil, and various organic substances from the hands. Plain soaps
have minimal, if any, antimicrobial activity. However,
handwashing with plain soap can remove loosely adherent tran-
sient flora. For example, handwashing with plain soap and
water for 15 seconds reduces bacterial counts on the skin by
0.6­1.1 log10, whereas washing for 30 seconds reduces counts
by 1.8­2.8 log10 (1). However, in several studies, handwashing
with plain soap failed to remove pathogens from the hands of
hospital personnel (25,45). Handwashing with plain soap can
result in paradoxical increases in bacterial counts on the skin
(92,95­97). Non-antimicrobial soaps may be associated with
considerable skin irritation and dryness (92,96,98), although
adding emollients to soap preparations may reduce their pro-
pensity to cause irritation. Occasionally, plain soaps have
become contaminated, which may lead to colonization of
hands of personnel with gram-negative bacilli (99).


B. When washing hands with soap and water, wet hands
   first with water, apply an amount of product
   recommended by the manufacturer to hands, and
   rub hands together vigorously for at least 15 seconds,
   covering all surfaces of the hands and fingers. Rinse
   hands with water and dry thoroughly with a
   disposable towel. Use towel to turn off the faucet
   (IB) (90-92,94,411). Avoid using hot water, because
   repeated exposure to hot water may increase the risk
   of dermatitis (IB) (254,255).
C. Liquid, bar, leaflet or powdered forms of plain soap
   are acceptable when washing hands with a non-
   antimicrobial soap and water. When bar soap is used,
   soap racks that facilitate drainage and small bars of
   soap should be used (II) (412-415).


E. Do not add soap to a partially empty soap dispenser.
   This practice of "topping off" dispensers can lead to
   bacterial contamination of soap (IA) (187,419).


412. McBride ME. Microbial flora of in-use soap products. Appl Environ
     Microbiol 1984;48:338­41.
413. Kabara JJ, Brady MB. Contamination of bar soaps under "in use" con-
     dition. J Environ Pathol Toxicol Oncol 1984;5:1­14.
414. Heinze JE, Yackovich F. Washing with contaminated bar soap is
     unlikely to transfer bacteria. Epidem Inf 1988;101:135­42.
415. Bannan EA, Judge LF. Bacteriological studies relating to handwashing:
     1. the inability of soap bars to transmit bacteria. Am J Public Health

Washing with contaminated bar soap is unlikely to transfer bacteria. Epidemiol Infect. 1988 Aug;101(1):135-42. Heinze JE, Yackovich F. Dial Corporation, Dial Technical Center, Scottsdale, AZ 85254.



    Recent reports of the isolation of microorganisms from used soap
    bars have raised the concern that bacteria may be transferred from
    contaminated soap bars during handwashing. Since only one study
    addressing this question has been published, we developed an
    additional procedure to test this concern. In our new method
    prewashed and softened commercial deodorant soap bars (0.8%
    triclocarban) not active against Gram-negative bacteria were
    inoculated with Escherichia coli and Pseudomonas aeruginosa to
    give mean total survival levels of 4.4 X 10(5) c.f.u. per bar
    which was 70-fold higher than those reported on used soap
    bars. Sixteen panelists were instructed to wash with the
    inoculated bars using their normal handwashing procedure. After
    washing, none of the 16 panelists had detectable levels of either
    test bacterium on their hands. Thus, the results obtained using
    our new method were in complete agreement with those obtained with
    the previously published method even though the two methods differ
    in a number of procedural aspects. These findings, along with
    other published reports, show that little hazard exists in routine
    handwashing with previously used soap bars and support the
    frequent use of soap and water for handwashing to prevent the
    spread of disease.

    PMID: 3402545 [PubMed - indexed for MEDLINE]