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Boston, Massachusetts, USA
December 31
Neuroscience Ph.D. ************************** Passionate about science education and outreach; enjoys a great discussion about the intersection of science and everyday life *************************** Currently a biomedical researcher at a Harvard University hospital - Areas of expertise: endocrinology, appetite and metabolism, neuroscience, biochemistry, molecular biology *************************** Areas of interest: science and art, science and society, science policy, books/films/music, reading great magazines, travel, learning new things and sparking new ideas, gardening/nature *** All Content Copyright Aliquot - do not reproduce without express permission ***

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OCTOBER 28, 2009 10:47AM

hand sanitizers - all they're cracked up to be?

Rate: 6 Flag

You'll find the portable versions in grocery stores and drug stores, and large dispensers are increasingly found in public places.  But are hand sanitizing gels more effective than hand washing?  And how accurate are the claims that these gels can kill 99% of viruses and bacteria found on our skin?

The FDA recommends hand washing with soap and water - with hand sanitizer only as an adjunct.  The CDC recommends a high quality hand sanitizer gel if hands are not soiled, because proteins and fats (or any soiling of hands) can prevent effectiveness of the gels which can't cut through that grime.

The gel manufacturer's test results which claim to kill 99% of bacteria (often tests are carried out on inanimate surfaces) may not be accurate for skin.  And the amount and type of viruses killed are not certain either.  Recent reports suggest certain types of hand sanitizers may be effective in reducing numbers of H1N1 virus, and a 2008 study of a blend of an ethanol-based sanitizer with other ingredients showed improved inactivation of enteric viruses known to cause food-related illnesses (Macinga et al., Appl Environ Microbiol).  However, viruses and bacteria are resilient and not all hand sanitizers will kill all types of viruses or bacteria.  

The concensus advice appears to be: wash your hands with soap and water if you can first - because clean hands respond better to hand sanitizers.  And if you're purchasing a hand sanitizer for personal use, make sure it contains  60-90 percent minimum alcohol concentration (ie: ethanol, isopropyl alcohol), which health officials deem necessary to kill most harmful bacteria and viruses (Emerging Infectious Diseases 2006). 

But since we know not everything will be killed - keep your hands away from your mouth and mucus membranes like your eyes, where harmful germs can enter your body.  The CDC states that influenza virus is destroyed by heat (167-212°F [75-100°C], but in addition several chemical germicides, including chlorine, hydrogen peroxide, detergents (soap), iodophors (iodine-based antiseptics), and alcohols are effective against human influenza viruses if used in proper concentration for a sufficient length of time.  The key part here regarding alcohols (the most common active ingredient in hand sanitizing gels) is PROPER CONCENTRATION for a SUFFICIENT LENGTH OF TIME. 

The Mayo Clinic has a great website outlining proper handwashing techniques, and proper use of hand sanitizer gels (  The key for the hand gels is that they should cover the entire surface of the hand and stay on the hand for 25 seconds or until hands are dry. 

Some studies also suggest that hand sanitizers can kill the good flora living on our skin, however studies are ongoing and currently there seems to be no concensus about whether this would have a harmful effect on health.  Healthy bacteria live in many areas of our body, including the skin and gastrointestinal tract (a great lay article about this is here: 




Another reference from Dr. Sanjay Gupta:




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I'm appaled that you would spout such alarmist nonsense!
I eat that stuff all the time, haven't gotten H1N1 yet!
On the other hand I have no hair....anywhere...anymore.
On the upside I'm very smooth for the pool!

Thanks, Andy... and be careful what you put in your mouth!
Doesn't this obsession with anti-bacterial products ultimately make us less resistant?
Jeff -
In some cases overuse of anti-bacterial products may lead to resistance. However, I didn't find any studies suggesting this was the case for hand sanitizing gels - since the active ingredient is often alcohol and not an antibiotic. But I think its an area worth the research! Will let you know if I find anything further.
Jeff -

The Gupta link includes this quote which may be helpful to you:
"if sanitizers could actually cause antibiotic resistance down the road. Many studies have looked into the issue and all evidence points to the answer being no."

Also - here is an abstract from a paper talking about household anti-microbial agents and resistance:

Microb Drug Resist. 2006 Summer;12(2):83-90.
Triclosan and antimicrobial resistance in bacteria: an overview.

Yazdankhah SP, Scheie AA, Høiby EA, Lunestad BT, Heir E, Fotland TØ, Naterstad K, Kruse H.

Triclosan is a widely used biocide that is considered as an effective antimicrobial agent against different microorganisms. It is included in many contemporary consumer and personal health-care products, like oral and dermal products, but also in household items, including plastics and textiles. At bactericidal concentrations, triclosan appears to act upon multiple nonspecific targets, causing disruption of bacterial cell wall functions, while at sublethal concentrations, triclosan affects specific targets. During the 1990s, bacterial isolates with reduced susceptibility to triclosan were produced in laboratory experiments by repeated exposure to sublethal concentrations of the agent. Since 2000, a number of studies have verified the occurrence of triclosan resistance amongst dermal, intestinal, and environmental microorganisms, including some of clinical relevance. Of major concern is the possibility that triclosan resistance may contribute to reduced susceptibility to clinically important antimicrobials, due to either cross-resistance or co-resistance mechanisms. Although the number of studies elucidating the association between triclosan resistance and resistance to other antimicrobials in clinical isolates has been limited, recent laboratory studies have confirmed the potential for such a link in Escherichia coli and Salmonella enterica. Thus, widespread use of triclosan may represent a potential public health risk in regard to development of concomitant resistance to clinically important antimicrobials.
Interesting post, Aliquot (and follow up response to Jeff).

I discovered your blog after our back and forth on another thread.

I will send a link mom will love this.

-David Logan
I really, really hope posting here will evetually get you a wide audience.

You present your information concisely, calmly and without judgement. You also seem to understand how well-intentioned people can misconstrue all the chatter in the media. You display graciousness and civility even toward people who have taken personal shots at you. (Although I must say Andy makes me laugh, and it looks like you took a while to catch on.)

I also commend you for your policy of keeping your personal life out of your posts -- why cloud the valuable information you are providing?

Anyway, you are doing a great service. I will be directing people your way. There may be occasions when I question what you pose, but know that I will do so with sincere respect.
ruicanuck -
Again, thanks so much for your honesty and kind words.

Yes, at first I did not 'get' Andy - but have come to appreciate his satirical responses! He's making great points behind the sarcasm.

And yes - I hope you do send people this way - thank you! I'm glad you've gathered my intent for being here on OS - I'm hoping to be one scientist attempting to break down the wall between us and non-scientists, so we can openly and honestly communicate. I think there is a lot of mystery about how science operates, which isn't good for anyone.

Please do question me whenever you see fit! I'm here to have discussions, not to lecture.

All best,
Hand sanitizers vs. hand washing has become especially important in hospital settings when dealing with microorganisms that produce a "hardy" spore, such as the bacteria Clostridium difficile, which causes a nasty hospital-acquired disease. The spores are resistant to alcohol and many other general disinfectants. Check it out at:
Thanks Steve and Little House!

Little House - nice to have a concrete example of when the alcohol gels may not be effective!
I do know one thing for a fact, Purel kills sperm! Once I confused it with something else, and boy did it STING but I didn't get pupped. I called my Dr the next day to make sure it wouldn't hurt me (after I realized what I did) and he laughed his ass off, relieved my fears and told me to be more careful next time.

Thanks, LadyMiko.