What are the 0.01% of germs that hand sanitizers can’t kill?
In: Chemistry
When I was doing some QC documentation for microbial tests we had something of an argument was to what it meant when there were no colonies found on the Petri dish. Did that mean that the material was perfectly sterile? What if we had tested 10 samples? Or a hundred? Might we have found a growth in just one plate in that number? Could we call the result for the the whole batch of material “zero” or just “less than one per <volume of test sample>”
Statistics get difficult when you are dealing with that sort of problem. So your 0.01% just means that they didn’t find any on test but you can’t be certain that there never will be.
Alcohol-based hand sanitizer kills basically everything it touches, the issue is that there are nooks and crannies in your skin where the hand sanitizer doesn’t reach. Any little microbes that find themselves in those areas can avoid the hand sanitizing effects. Because of this, they can’t say it kills 100% of bacteria because, if tested and any microbes grow, you could put yourself in legal trouble.
There are certain bacteria that are resistant to alcohol. One of the most well – known is Clostridium difficile (C. diff), specifically C. diff spores. When treating patients with C. diff, you’re supposed to take extra precautions to avoid spreading the spores because they are so robust and resistant to sanitization.
Well, first off the 99.99% or similar claims are meaningless and only serve as a marketing gimmick.
The number comes from their own tests in a highly specific laboratory conditions which doesn’t translate to the real world. So they can put that number on their products but what does it mean for you?
It means that they are not guaranteeing that they will kill all your germs, and that’s because it’s virtually impossible. Hands in general are pretty good in retaining germs on them, and when we talk about germs we could be talking about billions of germs.
Those two factors make it extremely hard, practically impossible to kill all of them from your hands, even if you do it over and over again. So you’ll never really be able to kill all of the germs on your hands, hence the not-100% claim (and in the real world, it’s also not going to come close to the claimed percentage either).
The same type that they do kill, they are just stating that in tests where, for example, there are 10,000 organisms, one will likely survive. No sanitizer can claim 100% effectiveness.
I don’t think they are inferring that there are particular germs that are immune to disinfectants. Instead, i think that is the success rate if applied to a surface following the directions for use. Basically, some random germs will make it and survive.
Norovirus is one of the common ones it can’t kill, but there are others, too. And always the potential for something new to show up it can’t kill — just be thankful it does work on the novel coronavirus we’re dealing with now!
**Please read this entire message**
—
Your submission has been removed for the following reason(s):
* ELI5 requires that you *search the ELI5 subreddit for your topic before posting*.
Users will often either find a thread that meets their needs or find that their question might qualify for an exception to rule 7.
Please see this [wiki entry](http://www.reddit.com/r/explainlikeimfive/wiki/how_to_search) for more details (Rule 7).
—
If you would like this removal reviewed, please read the [detailed rules](https://www.reddit.com/r/explainlikeimfive/wiki/detailed_rules) first. **If you believe this submission was removed erroneously**, please [use this form](https://old.reddit.com/message/compose?to=%2Fr%2Fexplainlikeimfive&subject=Please%20review%20my%20thread?&message=Link:%20https://old.reddit.com/r/explainlikeimfive/comments/hicanm/-/%0A%0AThe%20concept%20I%20want%20explained:%0A%0ALink%20to%20your%20search%20for%20past%20posts%20on%20the%20ELI5%20subreddit:%0A%0AHow%20is%20this%20post%20unique:) and we will review your submission.
Latest Answers