[Robert Lynn]

Robert Lynn  asked the Naked Scientists:
   
Especially now, with concerns about H1N1, people are using hand sanitizers more often but without "instructions" for their use. Beyond the mechanics, I would like to know how quickly sanitizers work after application and how long they last -- do they kill germs even after the initial application? I have become somewhat compulsive in their use; are there any concerns of overuse?

What do you think?

[Variola]

Unless it is C. Diff.....

Good old  fashioned hand washing with soap and water...can't beat it IMO.

[stereologist]

The appearance of H1N1 and MRSA in our area has prompted some of the businesses to post hand washing charts in the bathrooms. These charts show how to properly wash hands and give times to scrub. I've noticed that almost everyone is doing their part in properly scrubbing. It's good to know that people do take the time to be health sensitive.

[CurLz]

Hand Sanitizers work a little differently than most people think.

Hand Sanitizers kill 99.9% of the bacteria on your hands. The remaining 0.1% are the strongest, most developed bacteria. So, basically you're left with the strongest (worst) possable bacteria on your hands. These few strong bacteria that survive the hand sanitizer multiply until your hands are once again, covered in bacteria, except this bacteria cannot be destroyed by the current hand sanitizer. So, the hand sanitizer developers have to go and create a stronger hand sanitizer...and a stronger one....and a stronger one...etc.

Thus, hand sanitizers (in the long term) make the bacteria situation worse.

[yor_on]

I learnt that a good 'rule of thumb' as we say in Sweden is to assume that you by washing your hands with soap and water will get rid of approximately nienty percent of the germs and bacteria etc. If you then wash them again you will be down to only one percent left, assuming that you air dry them. And that percent won't be the 'meanest ones' as it will be in the example with Hand Sanitizers.

Also i would like to remind you all that as long as you're not doing surgical procedures germs and bacteria is a way to strengthen your immune system. To let your kids play in the dirt and even eat some earth (or other things:) won't kill them, in fact it seems to have the opposite effect, it will protect them as they grow up. There are several studies pointing to that assumption. You need to differ between a sterile environment as a 'operating theater' and what you meet outside it. Soap and water will work every time, and air dry them if you're going to do something 'sensitive'. It's quite enough.

[Bored chemist]

Hand Sanitizers work a little differently than most people think.

Hand Sanitizers kill 99.9% of the bacteria on your hands. The remaining 0.1% are the strongest, most developed bacteria. So, basically you're left with the strongest (worst) possable bacteria on your hands. These few strong bacteria that survive the hand sanitizer multiply until your hands are once again, covered in bacteria, except this bacteria cannot be destroyed by the current hand sanitizer. So, the hand sanitizer developers have to go and create a stronger hand sanitizer...and a stronger one....and a stronger one...etc.

Thus, hand sanitizers (in the long term) make the bacteria situation worse.

Most of these sanitisers us alcohol as the germicide.
As it happens, I'm rather partial to a drink or two on a Friday night. One aspect of this is that I have a rather higher alcohol tolerance than many (I don't know if that's cause or effect- it doesn't matter much here).
So, if the aliens land and pour the equivalent of half a bottle of whisk(e)y down everyone's neck, many people die but I survive.
The question is does this mean that I am in any meaningful sense the "worst possible", or just lucky?
Actually, what it probably means is that because of the damage done acquiring that tolerance or the effort I have to waste maintaining an oversized liver, I'm one of the weaker ones.
Since the body doesn't use alcohol to kill bugs those bugs that are resistant to alcohol have no advantage when it comes to a battle with the body's immune system.

Keep using the hand wash gel.

[CurLz]

Hand Sanitizers work a little differently than most people think.

Hand Sanitizers kill 99.9% of the bacteria on your hands. The remaining 0.1% are the strongest, most developed bacteria. So, basically you're left with the strongest (worst) possable bacteria on your hands. These few strong bacteria that survive the hand sanitizer multiply until your hands are once again, covered in bacteria, except this bacteria cannot be destroyed by the current hand sanitizer. So, the hand sanitizer developers have to go and create a stronger hand sanitizer...and a stronger one....and a stronger one...etc.

Thus, hand sanitizers (in the long term) make the bacteria situation worse.

Most of these sanitisers us alcohol as the germicide.
As it happens, I'm rather partial to a drink or two on a Friday night. One aspect of this is that I have a rather higher alcohol tolerance than many (I don't know if that's cause or effect- it doesn't matter much here).
So, if the aliens land and pour the equivalent of half a bottle of whisk(e)y down everyone's neck, many people die but I survive.
The question is does this mean that I am in any meaningful sense the "worst possible", or just lucky?
Actually, what it probably means is that because of the damage done acquiring that tolerance or the effort I have to waste maintaining an oversized liver, I'm one of the weaker ones.
Since the body doesn't use alcohol to kill bugs those bugs that are resistant to alcohol have no advantage when it comes to a battle with the body's immune system.

Keep using the hand wash gel.

Hmmmm, that's strange.
I aquired the "Hand sanitizers make the bacteria situation worse" theory from a professor at one of Canada's best universities for Biology. The professor had a PhD in Molecular Biology and Genetics. Soooo...ya, I'm assuming that he does infact know what he's talking about.

Where did you gather the information for your theory, "Keep using the hand wash gel"?
...just curious.

[Bored chemist]

You can see my reasoning. Please go and ask the authority to whom you are appealing to do the same.

BTW, appeal to authority as in "this guy has a PhD so he must be right" is a logical fallacy. If you wan to insist on it then I will see  your prof, and raise you the CDC.
http://www.cdc.gov/h1n1flu/qa.htm#e

[Madidus_Scientia]

Curlz I think you're confusing hand sanitizers with anti-biotics.

[yor_on]

Your professor is right when it comes to the operating table. Probably it was this situation that was in his mind, if I remember right though there is a time limit to how long that sterilization will work. But for situations outside that environment considering your general health a little dirt won't harm you Here's a nice description of my view

[Yair Doza]

As it happens I heard the answer on the pod cast of the naked scientist. Some viruses such as the influenza flu virus have an oily coating. The alcohol in the sanitizer dissolves the alcohol 'killing' the virus in 30 seconds. Other viruses as the vomiting bug have hard dry coating so they are not removed by the gel hand wash - soap and water will remove them. To be safe wash your hands and use a gel!

[cheryl j]

The only thing I am aware of that hand sanitizers do not kill are endospore forming bacteria like C. difficile.

[Phil1907]

You need to consider context that bacteria are rarely encountered, beyond the artifical construct of lab cultures, as isolated cells prone to alcohol kill. Hand santizers are qualified on the basis of their kill of freshly applied lab grown single cells cultures on hands.  Bacteria under fingernails in adjacent folds and in soils are not substantially affected.

Vegetative bacteria in biofilm are also not killed even if immersed in alcohol.
Infect Control Hosp Epidemiol. 2004 Mar;25(3):231-9.  Outbreak of Burkholderia cepacia bacteremia traced to contaminated hospital water used for dilution of an alcohol skin antiseptic.