The higher the alcohol concentration, the better the disinfection effect? ​​This statement is really wrong!

When it comes to medical alcohol, everyone is familiar with it. It is a disinfectant that is often available in household medicine boxes and medical institutions. During the fight against the new coronavirus epidemic, good hand hygiene is an important part of disease prevention. Among all kinds of disinfectants, the ability of alcohol should not be underestimated. However, many people have a cognitive misunderstanding about alcohol, that is, "the higher the alcohol concentration, the better the disinfection effect." In fact, the concentration of alcohol for disinfection should be between 70% and 75%. If the alcohol concentration is too high, it will not be conducive to the penetration of alcohol into the pathogen and will not achieve the disinfection effect.

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01

Alcohol's unrivaled disinfecting power

The biggest advantage is that the killing range is wide enough

Ways to maintain good hand hygiene include: washing hands with soap and water, disinfecting hand sanitizer (alcohol-based hand sanitizer, etc.), foam or gel hand sanitizer, etc. Alcohol is increasingly favored by people because it is easy to use, does not stain, has an acceptable odor, starts quickly and has a wide range of antibacterial activity.

The most prominent advantage of using alcohol for disinfection is that it is effective against a variety of pathogens. According to the Centers for Disease Control and Prevention (CDC), alcohol is effective against most Gram-positive and Gram-negative bacteria, including multidrug-resistant pathogens, HIV, influenza virus, vaccinia, hepatitis B and hepatitis C viruses, etc. Experiments have shown that alcohol is very effective in preventing seasonal influenza, H1N1 and other viral and bacterial-based diseases.

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02

Alcohol concentration is too high

It affects its permeability

Protein denaturation is the main way alcohol works against microorganisms. Alcohol changes the spatial structure of pathogen proteins, causing irreversible denaturation and coagulation, which results in the loss of activity of both structural and functional proteins, thus causing serious damage to pathogenic microorganisms.

At the same time, alcohol can also destroy the cell walls of bacteria. Alcohol has a strong penetrating effect, and this penetrating effect is best when the concentration is 60%-80%. It can enter the pathogen, destroy the integrity of the pathogen, and cause the pathogen to lyse. However, when the concentration reaches 90%, the disinfection effect of alcohol will decrease. This is because too high a concentration of alcohol will cause the protein on the outer surface of the pathogenic microorganism to coagulate quickly, forming a protective shell on the surface of the pathogenic microorganism, which will prevent alcohol from further entering the interior of the microorganism and cannot effectively exert the disinfection ability of alcohol.

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In addition, alcohol can interfere with the enzyme system of microorganisms. Enzymes are essential catalysts for the normal physiological activities and metabolism of various organisms. Studies have shown that ethanol can interfere with pathogen metabolism by directly affecting the enzyme system of pathogens.

03

Different concentrations of alcohol

Determines the occasions where it will work

The alcohol commonly used in hospitals includes 75% and 95% concentrations. The alcohol used for disinfection is 75% concentration, which is often used to disinfect skin and medical equipment. It is worth noting that alcohol is irritating and cannot be used to disinfect mucous membranes and large wounds.

95% alcohol is often used as fuel and can be found in various alcohol lamps and alcohol stoves. It can also be used in the fixation and dehydration steps of pathological tissue sections. In addition, 40%-50% alcohol can be used to prevent bedsores. Bedridden patients are prone to bedsores due to long-term pressure on local tissues, continuous ischemia, hypoxia, and malnutrition of local tissues. Once bedsores are formed, they are difficult to heal. Using alcohol when turning over and scrubbing can promote local blood circulation and help prevent bedsores. Alcohol also has the effect of evaporating heat and promoting vasodilation, so 20%-50% alcohol is often used for physical fever reduction.

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04

Proper use of alcohol

Better play its role

It is important to emphasize that liquor cannot replace medical alcohol. The alcohol concentration of most liquors is roughly 20%-65%, while the recommended concentration of medical alcohol for disinfection is 70%-75%. Liquor cannot kill microorganisms as effectively as medical alcohol, but in the absence of alcohol, liquor can be used as an emergency disinfection treatment.

During the epidemic, some people spray alcohol indoors to achieve the effect of disinfection, but this is actually unnecessary. The Centers for Disease Control and Prevention (CDC) clearly stated in the Environmental Guidelines and the 2008 Disinfection and Sterilization Guidelines: It is not recommended to use alcohol for environmental disinfection. This is because the disinfection area is too large, the alcohol evaporates quickly, and the contact time with the surface of the object is short, so it cannot achieve a good disinfection effect.

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Recently, the COVID-19 epidemic has fluctuated again in some areas. We should ventilate frequently, wash hands frequently, and try to reduce going out. At the same time, we should strive to enhance our immunity and avoid gathering in crowded places. Wearing a mask when going out is the top priority in preventing the new coronavirus. If conditions permit, it is recommended to use alcohol for disinfection to protect yourself and your family.

Author: Gao Wenzhen, School of Stomatology, Shandong University

Wu Yibo Department of Pharmacy Management and Clinical Pharmacy, School of Pharmaceutical Sciences, Peking University

Review | Tang Qin, Researcher, Science and Technology Popularization Department, Chinese Medical Association

References:

Chen Luyao, Wu Shouli, Lin Liwang, et al. Evaluation of the disinfection effect of different commonly used disinfectants on HIV[J]. Chinese Journal of Public Health, 2013, 29(8):1111-1114.

TODD, EWEN C. D, MICHAELS, BARRY S, HOLAH, JOHN, et al. Outbreaks Where Food Workers Have Been Implicated in the Spread of Foodborne Disease. Part 10. Alcohol-Based Antiseptics for Hand Disinfection and a Comparison of Their Effectiveness with Soaps[J]. J Food Prot, 73(11):2128-2140.

Boyce JM . Alcohols as Surface Disinfectants in Healthcare Settings[J]. Infection Control and Hospital Epidemiology, 2018, 39(3):1-6.Efficacy of ethanol against viruses in hand disinfection

Larson, Elaine L, Cimiotti, Jeannie, Haas, Janet, et al. Effect of Antiseptic Handwashing vs Alcohol Sanitizer on Health Care–Associated Infections in Neonatal Intensive Care Units[J]. Arch Pediatr Adolesc Med, 159(4):377.

Maiwald M , Chan ESY . The Forgotten Role of Alcohol: A Systematic Review and Meta-Analysis of the Clinical Efficacy and Perceived Role of Chlorhexidine in Skin Antisepsis[J]. PLOS ONE, 2012, 7.

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