CDC Review of Soap Types

By September 20, 2010 Hand Care

The CDC has published some recommendations regarding hand hygiene preparations. Here are some excerpts:

Plain (Non-Antimicrobial) Soap

Kids washing handsSoaps are detergent-based products that contain esterified fatty acids and sodium or potassium hydroxide. They are available 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 transient flora. For example, handwashing with plain soap and water for 15 seconds reduces bacterial counts on the skin, whereas washing for 30 seconds reduces counts by over twice as much. However, in several studies, handwashing with plain soap failed to remove pathogens from the hands of hospital personnel. Handwashing with plain soap can result in paradoxical increases in bacterial counts on the skin.


Active ingredient ethanolAlcohols have excellent in vitro germicidal activity against gram-positive and gram-negative vegetative bacteria, including multidrug-resistant pathogens (e.g., MRSA and VRE), Mycobacterium tuberculosis, and various fungi. Certain enveloped (lipophilic) viruses (e.g., herpes simplex virus, human immunodeficiency virus [HIV], influenza virus, respiratory syncytial virus, and vaccinia virus) are susceptible to alcohols when tested in vitro. Hepatitis B virus is an enveloped virus that is somewhat less susceptible but is killed by 60%–70% alcohol; hepatitis C virus also is likely killed by this percentage of alcohol. In a porcine tissue carrier model used to study antiseptic activity, 70% ethanol and 70% isopropanol were found to reduce titers of an enveloped bacteriophage more effectively than an antimicrobial soap containing 4% chlorhexidine gluconate. Despite its effectiveness against these organisms, alcohols have very poor activity against bacterial spores, protozoan oocysts, and certain nonenveloped (nonlipophilic) viruses.

Numerous studies have documented the in vivo antimicrobial activity of alcohols. Alcohols effectively reduce bacterial counts on the hands. Alcohols are rapidly germicidal when applied to the skin, but they have no appreciable persistent (i.e., residual) activity. However, regrowth of bacteria on the skin occurs slowly after use of alcohol-based hand antiseptics, presumably because of the sublethal effect alcohols have on some of the skin bacteria. Addition of chlorhexidine, quaternary ammonium compounds, octenidine, or triclosan to alcohol-based solutions can result in persistent activity.

Alcohol-based products are more effective for standard handwashing or hand antisepsis by health care workers (HCWs) than soap or antimicrobial soaps. In all but two of the trials that compared alcohol-based solutions with antimicrobial soaps or detergents, alcohol reduced bacterial counts on hands more than washing hands with soaps or detergents containing hexachlorophene, povidone-iodine, 4% chlorhexidine, or triclosan. In studies examining antimicrobial-resistant organisms, alcohol-based products reduced the number of multidrug-resistant pathogens recovered from the hands of HCWs more effectively than did handwashing with soap and water.

Antimicrobial Soap with Triclosan

Doctor washing handsTriclosan (chemical name: 2,4,4′ –trichloro-2′-hydroxy-diphenyl ether) is a nonionic, colorless substance that was developed in the 1960s. It has been incorporated into soaps for use by HCWs and the public and into other consumer products. Concentrations of 0.2%–2% have antimicrobial activity. Triclosan enters bacterial cells and affects the cytoplasmic membrane and synthesis of RNA, fatty acids, and proteins. Recent studies indicate this agent’s antibacterial activity is attributable to binding to the active site of enoyl-acyl carrier protein reductase.

Triclosan has a broad range of antimicrobial activity, but it is often bacteriostatic. Triclosan’s activity against gram-positive organisms (including MRSA) is greater than against gram-negative bacilli, particularly P. aeruginosa. The agent possesses reasonable activity against mycobacterial and Candida spp., but it has limited activity against filamentous fungi. In several studies, log reductions have been lower after triclosan is used than when chlorhexidine, iodophors, or alcohol-based products are applied.

Read the full report.