Research for infection protection

Hand disinfectants: better antimicrobial activity by sufficiently high ethanol contents

Healthcare workers are advised to use alcohol-based hand disinfectants for routine hand disinfection. The preparations’ efficacy depends on the application time, quantity applied and alcohol concentration. One of the commonly used active ingredients is ethanol (C2H5OH). Ethanol concentrations can be expressed as percentage by volume (v/v) and percentage by weight (w/w). Read on to find out how to convert for ethanol percentage by volume to/from percentage by weight.

For a hand disinfectant to be listed as effective for hygienic hand disinfection, it needs to fulfil the requirements for bactericidal activity (according to EN 1500). Virucidal activity is optional and is tested in accordance with EN 14476. Products with relatively low ethanol concentrations of up to 70 % (w/w) usually are not sufficiently effective for hygienic hand disinfection, when 3 ml are applied for 30 seconds. Particularly gels are considered less effective than liquid products as they contain less ethanol. Also, products with low ethanol contents hardly achieve virucidal activity.

There have been several scientific studies on a number of hand disinfectants with different concentrations of ethanol. The following figure shows the relationship between ethanol content and antimicrobial efficacy. These data are based on the application of 3 ml over 30 seconds.

Ethanol content in hand disinfectants – application tool

Click on the percentage and read studies on the efficacy of hand disinfectants with different ethanol concentrations under SCIENCE:

60-70%

Kramer A et al. 2002
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70%

Kampf G et al. 2013
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73.5%

73.5 % w/w is equal to 80 % v/v.

Suchomel M et al. 2012
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78.2%

Kampf G et al. 2003
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80%

Suchomel M et al. 2012
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85%

Kampf G et al. 2002
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Studies on ethanol-based hand disinfectants

  • Ethanol content of up to 70 %
    A study came to the conclusion that hand gels with ethanol concentrations ranging between 53 and 70 % (v/v) are not sufficiently effective in accordance with EN 1500 (3 ml within 30 seconds) [1]. A recent analysis found that a hand gel and liquid product, each containing 70 % ethanol (w/w), are not sufficiently active against bacteria in accordance with EN 1500 [2]. Kramer et al. recommend that "ethanol-based hand gels used in hospitals should contain at least 80 % (v/v) ethanol as active ingredient" [1].

  • Ethanol content of 70 - 80 %
    In terms of antimicrobial efficacy of ethanol-based hand disinfectants, there is a grey area between ethanol concentrations of 70 % and 80 %. A liquid preparation with 78.2 % (w/w) ethanol met the efficacy requirements with 3 ml within 30 seconds [3]. However, a WHO study showed that a product with 73.5 % (w/w) ethanol is not sufficiently active when applied in the same manner. As soon as the authors increased the ethanol concentration to 80 % (w/w), the product fulfilled the EN 1500 efficacy criteria [4].

  • Ethanol content of 80 % and higher
    Users who want to play safe select a product with an ethanol concentration of at least 80 % (w/w). A hand gel based on 85 % (w/w) ethanol proved to be effective and met the efficacy requirements four times over [5]. This means that also gel products are suitable for hygienic hand disinfection as long as they contain sufficiently high concentrations of active ingredient.

Literature

  1. Kramer A et al. 2002 Limited efficacy of alcohol-based hand gels. The Lancet 2002, 359: 1489-1490.
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  2. Kampf G et al. 2013 Efficacy of hand rubs with a low alcohol concentration listed as effective by a national hospital hygiene society in Europe. Antimicrobial Resistance and Infection Control 2013, 2: 19.
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  3. Kampf G et al. 2003 Comparison of two test methods for the determination of sufficient antimicrobial efficacy of three different alcohol-based hand rubs for hygienic hand disinfection. Journal of Hospital Infection 2003, 55 (3): 220-225.
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  4. Suchomel M et al. 2012 Testing of the World Health Organization recommended formulations in their application as hygienic hand rubs and proposals for increased efficacy. Am J Infect Control 2012, 40 (4): 328-331.
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  5. Kampf G et al. 2002 Spectrum of antimicrobial activity and user acceptability of the hand disinfectant agent Sterillium Gel. Journal of Hospital Infection 2002, 52(2):141-147.
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