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Chemistry science fair project:
Effectiveness of Non-Alcohol vs. Alcohol-Based Hand Sanitizer




Science Fair Project Information
Title: Effectiveness of Non-Alcohol vs. Alcohol-Based Hand Sanitizer
Subject: Chemistry
Grade level: Elementary School - Grades 4-6
Academic Level: Ordinary
Project Type: Experimental
Cost: Medium
Awards: 2nd place, Washington State Science and Engineering (2006)
Affiliation: Selah Intermediate School
Year: 2006
Description: Subjects' palm was swabbed for bacteria sampling. The manipulated variable was the type of cleanser. The responding variable was the number of colonies visible, using the naked eye in white light, on blood agar plates after incubation.
Link: http://www.selah.k12.wa.us/SOAR/SciProj2006/DalaineeV.html
Short Background

Hand sanitizer is a non-water-based hand hygiene agent. In the late 1990s and early part of the 21st century, non-water-based hand hygiene agents (also known as alcohol-based hand rubs, antiseptic hand rubs, or hand sanitizers) began to gain popularity. Most are based on isopropyl alcohol or ethanol formulated together with a thickening agent such as Carbomer, and a humectant such as glycerin into a gel, liquid, or foam for ease of use and to decrease the drying effect of the alcohol.

Hand sanitizers containing a minimum of 60 to 95% alcohol are efficient germ killers. Alcohol rub sanitizers kill bacteria, multi-drug resistant bacteria (MRSA and VRE), tuberculosis, and viruses (including HIV, herpes, RSV, rhinovirus, vaccinia, influenza, and hepatitis) and fungus. Alcohol rub sanitizers containing 70% alcohol kill 3.5 log10 (99.9%) of the bacteria on hands 30 seconds after application and 4 to 5 log10 (99.99 to 99.999%) of the bacteria on hands 1 minute after application. Alcohol rub sanitizers can prevent the transfer of health-care associated pathogens (Gram-negative bacteria) better than soap and water.

The increasing use of these agents is based on their ease of use and rapid killing activity against microorganisms.

However frequent use of alcohol-based formulations for hand sanitizers can cause dry skin unless emollients and/or skin moisturizers are added to the formula. The drying effect of alcohol can be reduced or eliminated by adding glycerin and/or other emollients to the formula. In clinical trials, alcohol based hand sanitizers containing emollients caused substantially less skin irritation and dryness than soaps or antimicrobial detergents. Allergic contact dermatitis, contact urticaria syndrome or hypersensitivity to alcohol or additives present in alcohol hand rubs rarely occurs. The lower tendency to induce irritant contact dermatitis also become an attraction as compared to soap and water hand washing.

Despite their effectiveness, the non-water agents do not clean hands of organic material, they simply disinfect them. However, disinfection does prevent transmission of infectious microorganisms. The commercial products of those include the brands of Aqium, Germ Warfare, Cuticura et cetera and Rochon-Edouard et al. has provided a good review of those products.

The efficacy of alcohol-free hand sanitizers is heavily dependent on their ingredients and formulation. In the past, alcohol-free hand sanitizers tended to significantly under-perform alcohol or alcohol rubs as germ killers in clinical studies using standard protocols such as EN1500. More recently, advanced formulations have been developed, some of which have been shown to out-perform alcohol. A further aspect of efficacy that is sometimes overlooked is the effect of repeated use. The efficacy of alcohol as a hand disinfectant has been shown to decrease after repeated use, probably due to progressive adverse skin reactions, whereas the efficacy of an alcohol-free hand sanitizer based on Benzalkonium Chloride as its active ingredient has been shown to increase with repeated use.

Alcohol rubs (biocides) kill microorganisms. Current scientific evidence has not demonstrated a link between the use of topical antimicrobial formulations and antiseptic or antibiotic resistance. Antiseptics (biocides) have multiple (thousands) of nonspecific killing sites on and in the microbial cell which cannot easily mutate. Antibiotics and antibacterial soaps (triclosan) have one very specific killing site on and in the microbial cell which can easily mutate. Antibiotic resistance has no effect on the effectiveness of antiseptics.

Alcohol rubs and combination hand sanitizers are effective at killing germs on the hands, but not effective at removing dirt. Many clinical studies have shown that alcohol rubs containing two germ killers (ie. Alcohol and Chlorhexidine gluconate or Benzalkonium chloride) are significantly better germ killers than alcohol rubs containing alcohol alone.

However alcohol rub sanitizers are not appropriate for use when the hands are visibly dirty, soiled or contaminated with blood. Visible soiling of any sort on the hands must be washed with soap and water because alcohol-based hand rubs are ineffective in the presence of organic material. In addition, alcohols are ineffective against non-lipid-enveloped viruses (e.g., Noroviruses) and the spores of bacteria (e.g., Clostridium difficile) and protozoa (e.g., Giardia lamblia). When such microorganisms are likely to be encountered, soap and water hand washing is preferable.

Both hand washing with hand sanitizer and with soap are effective in cleaning staph aureus, and the bacteria that are causing these staph infections, but alcohol-based hand sanitizers are not effective in killing other types of bacteria such as those from the gastro-intestinal tract, or hazards such as e-coli and salmonella because alcohol doesn't destroy spores, but washing hands washes the spores down the sink.

In the U.S. hand sanitizers being banned from some schools because of flammability concern. The fire department allows Tallahassee Memorial Hospital to have a certain about of hand sanitizer per smoke compartment, and supply it up to that limit.

Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License)

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