Maintaining hand hygiene has been established as crucial for reducing the colonization and incidence of infectious diseases in all populations. Compliance with hand hygiene recommendations is believed to play a significant role in decreasing the risk of gastroenteric and respiratory infections. Strict hand hygiene is even more important for health-care workers (HCW) as unclean hands may aid in the transmission of microorganisms from patient to patient, leading to increased morbidity, mortality, and costs associated with healthcare-associated infections (HCAI). In 2002, healthcare-associated infections (HCAI) were a cause of 99,000 deaths in the United States of America, and the 2004 annual economic impact of HCAI was estimated to be US$ 6.5 billion.
Evidence suggests that hand sanitization significantly reduces the transmission of healthcare-associated pathogens and the incidence of HCAI. Despite the emphasis on the importance of hand hygiene, recent studies show poor hand hygiene compliance in medical settings. According to the Center for Disease Control and Prevention (CDC), hand hygiene encompasses the cleansing of your hands using soap and water, antiseptic hand washes, alcohol-based hand sanitizers (ABHS), or surgical hand antiseptics. These days, alcohol-based hand sanitizers are increasingly being used instead of soap and water for hand hygiene in healthcare settings. Their ease of use increased availability, and proven effectiveness are some of the reasons why alcohol-based hand sanitizers are gaining popularity. In one study, a hospital-wide hand hygiene campaign with special emphasis on bedside alcohol-based hand disinfection resulted in sustained improvement in hand-hygiene compliance, coinciding with a reduction of nosocomial infections and MRSA transmission. A systematic review also demonstrated with moderate certainty that having bedside alcohol-based solutions increased compliance with hand hygiene among HCWs.
It is, however, important to keep in mind that the efficacy of alcohol hand sanitizers is dependent upon the type of alcohol, the quantity applied, the technique used, and the consistency of use. There are also situations where these products are not ideal, for example, in preventing the spread of certain alcohol-resistant infections or when hands are significantly soiled and the bacterial load is too high.
Alcohol-based (hand) Rub
The World Health Organization (WHO) defines an alcohol-based hand rub as: "An alcohol-containing preparation (liquid, gel or foam) designed for application to the hands to inactivate microorganisms and/or temporarily suppress their growth. Such preparations may contain one or more types of alcohol, other active ingredients with excipients, and humectants.”
Alcohol-based hand antiseptics mostly contain isopropanol, ethanol, n-propanol, or a mixture of these as their active ingredients. The antimicrobial activity of alcohols is attributed to their ability to denature and coagulate proteins. This causes microbes to lose their protective coatings and become non-functional. The Center for Disease Control and Prevention recommends formulations containing 80% (percent volume/volume) ethanol or 75% isopropyl alcohol, however, generally speaking, sanitizers containing 60 to 95% alcohol are acceptable. The recommended percentages of ethanol and isopropyl alcohol are kept as 80% and 75% because these values lie in the middle of the acceptable range. Notably, higher than recommended concentrations are also paradoxically less potent because proteins are not denatured easily without the presence of water. Alcohol concentrations in antiseptic hand rubs are often expressed as percent by volume and rarely as percent by weight. A study conducted on 85% (weight/weight) ethanol, showed that a 15 seconds contact time was enough to reduce gram-positive and negative bacteria by greater than 5 log10 steps. Research suggests that alcohols are swiftly germicidal when applied to skin, but have no noticeable persistent residual activity. However, it has been documented that the regrowth of bacteria does occur slowly after its use. This may be because of the sublethal effect alcohol may have had on the residual bacteria. Adding chlorhexidine, octenidine, or triclosan to alcohol-based hand rubs may result in somewhat persistent protection as well. 4% chlorhexidine has shown persistent bactericidal activity against methicillin-resistant Staphylococcus aureus for up to 4 hours from application.
Ethanol, the most common alcohol ingredient, appears to be the most effective alcohol against viruses, whereas, propanol is considered to be a better bactericidal alcohol. The combination of alcohols may also have a synergistic effect. The concentration of alcohol in hand sanitizers also changes its efficacy, with one study demonstrating that a hand rub with 85% ethanol content was significantly better at reducing bacterial populations compared to preparations of 60% to 62% ethanol. ABHS also often contain humectants, like glycerin, which help prevent skin dryness, and emollients or moisturizers, like aloe vera, which help replace some of the water that is stripped off during use. None of the above-mentioned alcohols have shown a potential for acquired bacterial resistance, and are therefore considered highly effective for repeated use in medical settings.
Alcohol-based sanitizers are very effective at quickly destroying a variety of pathogens and that too without the need for water, plumbing, and drying facilities. According to the World Health Organization (WHO), alcohols have an excellent activity against gram-positive bacteria, gram-negative bacteria, enveloped viruses, non-enveloped viruses, mycobacteria, and even fungi. Numerous studies have also documented the in-vivo antimicrobial activity of alcohols and the effectiveness in removing clinical strains of Acinetobacter baumannii, methicillin-resistant Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, and Candida albicans from profoundly contaminated hands of human volunteers.
A study published in the Journal of Infectious Diseases evaluated the virucidal activity of alcohol-based hand sanitizers (ABHS) against re-emerging viral pathogens, such as Ebola virus, Zika virus, severe acute respiratory syndrome coronavirus (SARS-CoV), and Middle East respiratory syndrome coronavirus (MERS-CoV). It determined that these pathogens, as well as other enveloped viruses, could also be efficiently inactivated alcohol. This further supports the use of ABHS in healthcare settings and viral outbreaks. More recently, alcohol-based sanitizers are also considered effective in preventing the hand-to-mucous membrane transmission of SARs-CoV-2, the pathogen responsible for the COVID-19 pandemic across the world. Alcohol-based sanitizers are thus considered useful in both hospital and community settings. 
Keeping in mind its excellent coverage against nearly all pathogens and lack of resistance development, alcohol-based hand sanitizers can be used in a variety of settings not limited to clinics, hospitals, acute care facilities, emergency medical centers, mobile healthcare units, nursing homes, and the community in general.
Generally speaking, alcohols are considered safer than detergents. Even though the absolute contraindication of alcohol-based hand sanitizers (ABHS) is limited to severe allergic reactions (such as anaphylaxis to aliphatic alcohols), there are a few concerns to its use. Despite the addition of emollients and moisturizers to modern preparations, ABHS is associated with a variety of skin reactions. Contact irritant dermatitis, which may vary in intensity from mild to concerning, can present as dryness, itching, irritation, pruritis, and skin cracking. Similarly, allergic contact dermatitis can also vary from mild to severe symptoms and may sometimes be accompanied by respiratory distress. Even though less widely reported, contact urticaria syndrome has also been associated with alcohol sanitizer use. It presents as swelling, redness, burning sensation, tingling, and/or itching within minutes (up to an hour) after application of alcohol. This urticarial reaction is localized and is characterized by wheal-and-flare. Research indicates that ethanol tends to be less irritating than n-propanol or isopropanol.
Some studies have also posed the question of possible health effects related to unintentional alcoholization (via inhalation and dermal contact) from frequent professional usage of alcohol-based hand sanitizers. Other studies have also documented measurable alcohol levels in healthcare workers who sanitized their hands 30 times per day. These levels are considered well in the safe zone; however, additional research is warranted to analyze and further evaluate the long-term health risks and effects on the fetuses of pregnant healthcare workers.
Even though not considered a contraindication but alcohol-based hand sanitizers have shown to be inferior to soap and water against certain pathogens. For instance, alcohols have very poor activity against protozoan oocysts, certain non-enveloped (non-lipophilic) viruses, and bacterial spores. Cryptosporidium, a waterborne parasite considered an important cause of diarrheal outbreaks in daycares, is not effectively killed by alcohol. Similarly, alcohol-based hand sanitizers are also considered ineffective against norovirus, a non-enveloped single-stranded positive-sense RNA virus. One study even found an association between the use of ABHS for routine hand hygiene and an increased risk of outbreaks of norovirus. Despite the fact that alcohol-based hand sanitizers are considered relatively subpar against nonenveloped viruses, in-vivo activity against some non-enveloped viruses has been documented. Studies have found that alcohol sanitizers reduce the infectivity titers of 3 non-enveloped viruses namely, rotavirus, adenovirus, and rhinovirus. Studies have also indicated that the addition of acid to alcohol-based hand sanitizers substantially improves the effectivity of ethanol against poliovirus, calicivirus, polyomavirus, and coxsackievirus. Another pathogen that alcohol-based hand sanitizers have proven to be ineffective against is clostridium difficile spores. Bacterial spores are considered some of the sturdiest organisms to kill and studies have demonstrated handwashing with soap to be superior to alcohol-based hand sanitizer use.
Other potential areas of concern with the use of alcohol-based hand sanitizers are the inadequate bactericidal and virucidal effect under long fingernails and visibly soiled hands.
The World Health Organization has recommended two formulations for alcohol-based hand sanitizers keeping in mind its cost effectiveness and microbicidal activity.
Additional chemicals that may be present in some formulations include aloe vera, moisturizers, chlorhexidine, triclosan, acids, and other alcohols.
The efficacy of alcohol-based hand sanitizers is dependent on the technique of application and its usage. Even though there are no strict guidelines, most researchers suggest the application of the sanitizer to the palm and thorough rubbing all over both hands until they are dry. There have been several studies comparing the amount needed to be effective and there have been varying recommendations ranging from 1.1 mL to 3.0 mL. FDA recommends a quantity of 2.4 mL as sufficient. Similarly, the application time also varies from 15 seconds to 30 seconds with most data lying somewhere in the middle. Care must be taken when using alcohol-based hand sanitizers in clinical settings as some pumps do not give out the recommended volume of sanitizer with one use.
A concern regarding the use of alcohol-based hand sanitizers (ABHS) is unintended pediatric ingestions. Ethanol-based hand sanitizers can cause alcohol poisoning if a person swallows more than a couple of mouthfuls. United States, National Poison Data System reports 65,000 incidences of ingestion between 2011 and 2014. Several studies have found that the ingestion of ethanol from hand sanitizers can induce intoxication and hypoglycemia in children. Older children have been known to swallow hand sanitizers to become drunk purposefully as well. The use of alcohol-based hand sanitizers is also associated with a small but measurable risk for fires and burns. Alcohol vapor may be easily flammable and care must be taken to use ABHS away from fire. Additionally, personnel applying ABHS should keep a safe distance from fires application as there is a risk of skin burning. Dermatological complications with the use of ABHS have been written in the section “contraindications”.
The use of alcohol-based hand sanitizers has greatly increased compliance to hand hygiene in healthcare settings. They are efficient, accessible, and take relatively little time to use. Even though there are some situations where they are perhaps less effective than standard soap and water, if using ABHS results in more consistent hand hygiene, it may be worth the trade-off. Guidelines regarding the use of soap and water instead of ABHS can be established keeping in mind the prevalent pathogens in a particular setting.
There is no longer any doubt that hand hygiene can lower transmission rates of pathogens. Hand washing is often not practical, and hence the alternate use of alcohol sanitizers may overcome this restraint. Alcohol sanitizers may be used both outside and inside healthcare facilities as they are effective at killing most microorganisms better than just soap and water. There are several formulas of alcohol sanitizers that are available in gel, foam, or liquid preparations. All healthcare workers should not only use alcohol sanitizers regularly but also educate the public about its benefits. Within a few seconds, alcohol can kill most non-spore-forming bacteria and decrease rates of infections. Data show that alcohol sanitizers definitely improve hand hygiene and reduce transmission of microorganisms in hospital settings. The major problem with the use of alcohol sanitizers is the lack of awareness; thus education and constant reinforcement about its benefits is needed.
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