Most of the alcohol-based antibacterial hand soaps contain isopropanol, ethanol, n-propanol or a combination of two of them.
The antimicrobial activity of alcohol has been attributed to its ability to denature proteins. Solutions containing 60 percent
to 90 percent alcohol are most effective; higher concentrations are less potent because proteins are not easily denatured
in absence of water.
The alcohol content of solutions may be expressed as a percentage by weight (w/w), which is not affected by temperature or
other variables; it may also be expressed as a percentage by volume (vol/vol), which can be affected by temperature, specific
gravity and/or reaction concentration.
For example, 70 percent alcohol by weight is equivalent to 76.8 percent by volume if prepared at 15 degrees Centigrade, or
80.5 percent if prepared at 25 degrees Centigrade. Alcohol concentrations in antiseptic hand rubs often are expressed as a
percentage by volume.
Alcohols have excellent in-vitro germicidal activity against gram-positive and gram-negative bacteria, Mycobacterium tuberculosis,
various fungi and some enveloped (lipophilic) viruses. Alcohols have poor germicidal activity against bacterial spores, protozoan
oocysts and some non-enveloped (non-lipophilic) viruses.
Alcohols effectively reduce bacterial counts on hands. The FDA has classified 60 percent to 90 percent ethanol as a Category
1 agent (i.e., generally safe and effective in health-care workers' antiseptic hand-wash products). Alcohols should not be
used when hands are visibly dirty or contaminated with proteinaceous material.
Although alcohols are rapidly germicidal when applied to the skin, they do not have persistent residual activity. However,
regrowth of bacteria on the skin occurs slowly after use of alcohol-based antiseptics, presumably because of the sub-lethal
effects that alcohols have on some bacteria. Addition of chlorhexidine, quaternary ammonium compounds, octenidine or triclosan
to alcohol-based solutions can result in persistent activity.
At this time, alcohol-based products have proven more effective for standard hand washing or hand antisepsis by health-care
workers than plain soap or other types of antimicrobial soaps. Alcohol reduced bacterial counts on hands more than washing
hands with soaps or detergents containing hexachlorophine, chlorhexidine, quaternary ammonium compounds, provodine-iodine
Frequent use of alcohol formulations for hand antisepsis can cause painful drying and cracking of skin. In my experience,
painful cracking of skin adjacent to fingernails is especially bothersome. This can reduce compliance with standard operating
protocols for hygienic or surgical hand cleansing. Addition of emollients, humectants, and/or other skin-conditioning agents
to alcohol-based product formulations will reduce or eliminate this problem. Hospital staff should be educated about the value
of frequent use of hand-care products.
Chlorohexidine gluconate is a cationic bisbiguanide whose antimicrobic activity is attributable to attachment to, and subsequent
disruption of, cyto-plasmic membranes, resulting in precipitation of cellular contents. The immediate antimicrobial activity
of chlorohexidine occurs more slowly than that of alcohols.
Chlorohexidine has good activity against gram-positive bacteria, less activity against gram-negative bacteria and fungi and
minimal activity against tubercle bacilli. It is not sporicidal, but has in-vitro activity against some enveloped viruses.
The antimicrobial of chlorohexidine is minimally affected by the presence of organic material, including blood. However, because
it is a cationic molecule, its activity can be reduced by natural soaps, inorganic ions, nonionic surfactants and hand creams
containing anionic emulsifying agents.
Aqueous or detergent formulations containing 0.5 percent to 0.75 percent chlorohexidine are more effective than plain soap,
but they are less effective than antiseptic detergent preparations containing 4 percent chlorohexidine gluconate. Addition
of 0.5 percent to 1 percent chlorohexidine to alcohol-based preparations results in greater residual activity than alcohol
Other antiseptic soaps
For specific information about other antiseptics in soaps, including chloroxylenol, hexachlorophene, iodine, iodo-phors, quaternary
ammonium compounds and triclosan, please refer to an excellent review entitled Guidelines for hand hygiene in health-care settings, by John M Boyce, MD, and Didier Pittet, MD. It can be accessed on the CDC's Web site at