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In the U.S. and Europe hand sanitizers must be put through regulated lab testing to prove their efficacy. Many of these brands claim to kill 99.9% of all germs and although in a heavily controlled environment these results are achieved, research has proven that hand sanitizers true germicidal effects in everyday life can be significantly less than the figure advertised on the labels. Many times these products are only tested against a few "representative" microbes as well. Factors that can also affect the level of efficiency usually include the amount a type of hand sanitizer used and on how soiled the subject's hand is prior to usage. Alcohol has been proven to be the most effective antiseptic out of all, but even then a kill rate of 99.9% is a far cry from real world effectiveness .
In 1988 the first "no hand washing required" gel antiseptic appeared , PURELL© Instant Hand Sanitizer, revolutionizing the medical and food industry forever. Many other brands have surged since then and nowadays we can place all of these in 1 of 2 categories: Alcohol based, or Alcohol free. And many of these brands, falling in either categories boast the claim that they can kill 99.9% of all bacteria on their labels. Much skepticism though has arisen since then, with the mention of the topic on many blogs and science forums. Even members of the scientific community have approached the topic with doubt and it has driven them to conduct experiments to prove its efficacy .
There also seems to be some controversy about which type of hand sanitizer is more effective,alcohol based or non-alcohol based. For example, Germ X© Advanced Protection Hand Sanitizer ,which contains Benzalkonium chloride, claims to kill 99.9% of all germs in 15 seconds, just as a regular alcohol based Purell hand sanitizer would. And the brand Clean Well© has made hand sanitizers with "no harsh chemicals" and uses thyme extract instead but also claims a 99.9% effectiveness against germs.
Another point worthy of mention, is that not all alcohol based sanitizers are made the same. And it all comes down to the concentration of alcohol present. Despite the FDA's recommendation of using a concentration of alcohol between 60-95% for maximum efficacy, there are many products out there that use as low as 40% but are still claiming a 99.9% kill rate on the bottle, leading many consumers to confusion on whether this claim is true or not.
In the U.S , the FDA regulates the use of antiseptic hand washes, scrubs and rubs. The testing is performed by using a standardized method both "in vitro" and "in vivo" in compliance with the FDA's Tentative Final Monograph for Healthcare Antiseptic Drug Products (TFM). This highly controlled method typically involves extensive hand washing beforehand and the use of artificial contamination, which is where they selectively place certain types of microbes on the subjects hands. Then they place the product in question on the subject's hand and repeatedly reapply until reaching the bacteria reduction necessary to claim 99.9% efficacy. In Europe the testing method used is the European Standard 1500--1997 (EN 1500). Similarly, this method requires prior sterilization and then artificial contamination, in this case the subjects hands are soaked in the broth of a selected pathogen (E.Coli). The CDC (Center for Disease Control) does recognize the flaws in these methodologies though, stating that many of these protocols do not reflect actual usage patterns among healthcare workers and consumers. Clearly, these methods do not simulate a "normal", "everyday" scenario, where we're exposed to millions of different types of bacteria,viruses, dirt and debri and where cleaning habits before application can vary as well.
Microbiologist Jason Tetro of the Ottawa-based Centre for Research on Environmental Microbiology, conducted a study with a group of 8th graders in Ontario to see how effective 3 different hand sanitizers (Purell, President's Choice & Soapopular) were up against the germs found on their hands. The test results were that only 46-60% of all germs were eliminated between the respective brands. However, these companies were quite critical of the results , claiming that the study's methods were "unscientific," "misleading" and not representing their products "true potential". They also questioned if Tetro used the same "controlled protocol" that they use to test their products although clearly, this test wasn't meant to be in a controlled setting , but to see the efficacy of the product in a real life scenario.
The CDC does mention another factor that can hinder the efficacy of hand sanitizer. Hand sanitizers (especially alcohol based ones) work by denaturing proteins, but if there is a presence of grime or dirt on a subjects hand it can serve as a protective layer for the germs , rendering the product less effective. As Tetro summarizes, "Essentially, it's the soiling of hands that can prevent a hand sanitizer from working properly ".
Another contributing factor to the level of efficiency of a hand sanitizing product is the active ingredient and its concentration. According to the CDC, "Many studies have found that sanitizers with an alcohol concentration between 60%–95% are more effective at killing germs than those with a lower alcohol concentration or non-alcohol-based hand sanitizers". Alcohol, unlike other antiseptics, is able to eliminate both gram-negative and gram-positive bacteria. But despite its effectiveness against these organisms, alcohols have very poor activity against bacterial spores, protozoan oocysts, and certain non enveloped viruses. Even then though, many other antiseptics containing other active ingredients such as Chlorhexidine, Triclosan, Benzalkonium or even essential oils claim to also kill 99.9% of all germs. But how is this possible if they have been proven to be even less effective than alcohol based sanitizers? A study in 2016 was conducted at the Department of Microbiology, Government Medical College, Dhule, Maharashtra, India. There they put to the test 4 different brands of hand sanitizers, one of them being PureHands which contained nothing else but plant extracts such as Coriander, Lime and Neem yet still claimed to kill 99.9% of all germs.Purehands though, ended up being quite significantly the least effective out of the 4 tested hand sanitizers and the researchers concluding stating: "Despite the claims of efficacy and 99.9% bacterial reduction by hand sanitizer manufacturers, there still exists a need for verification of these claims by regulatory bodies and higher authorities for the enforcement of good-quality measures." A preliminary study conducted in 2015 by a different researcher with the same products achieved very similar results as well.
In conclusion, the methods used for testing hand sanitizers clearly don't reflect real world usage. As Tetro states, "In a real life situation, we don't know how clean those hands are and so you're not going to see anywhere near the type of results [identified on the bottle]".Many consider that Federal regulations and testing for these products must be revised and updated. In result, the FDA in 2015 has proposed to reform the TFA document from 1994 which includes adding in vivo clinical simulation studies showing that specified logarithmic reductions in the amount of certain bacteria are achieved using the ingredient. Testing in these realistic settings could help us understand more about how these products really work in our everyday life.