"Kills 99.9% of household germs" - is this meaningless?

Sounds good, but does it mean:
• Kills 99.9% of the total mass of germs it comes into contact with?
Or
• Kills 99.9% of the variety of germs? (Possibly leaving just a few invincible species which could make up half of the total mass of germs)
Or
Is it just a marketing slogan that the conglomerates can get away with because no one has called them to prove their claim - which smacks of “spurious precision”?

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The 99.9% effective claim discussion has been aired on this site before. It is used because no absolute (100%) can be guaranteed, particularly so in households where air borne pathogens are always coming into contact with surfaces but this applies to almost everywhere humans or animals are.

What the claim purportedly raises is that the active ingredients are very effective and the claims use what may be termed puffery which again has been raised on this site (Truth in Advertising, should we accept Puffery). Basically it means the Law as it currently stands allows them to get away with it.

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… I remember someone quoting something as ‘unprovably non-disprovable’ or something equally confusing and probably grammatically murderous - maybe it was me, but I’ll not self-incriminate. Short answer - yes, in my view, statistics … :wink:

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There are a few posts in this topic citing 99.9% but the focal point of the topic might be relevant for you.

Getting through much of the chaff, some products are TGA registered and held to some standard regardless of how high (or low), and other products are essentially OTC cosmetics where puffery reigns supreme.

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Without following up the testing regime of any given product it is hard to say. Some may do general plate count of whatever bacteria grow from a given source (off your kitchen bench) before and after application of the product. It may be that some test for specific target species that have commonly available tests such as E.coli.

The claim means that the product has some antibacterial action. It doesn’t mean that under all circumstances it produces this result. It doesn’t really address the question of how valuable this ability may be.

If it kills 99.9% there are still one in a thousand left and if there were a thousand gazzillion in the first place there are still a gazzillion left. Without knowing what the specie is we don’t know if that is enough to be harmful. It is also probable that there are some specific species that are not killed by the product in significant quantities. For example there are groups that are practically speaking immune to 80% alcohol when most are killed.

A great many bacteria that you might get off your kitchen bench don’t do you any harm under normal circumstances. There are those in your gut that are very useful, there is a view that humans are not a single species but a symbiosis between our tissue and that of the bugs in our gut.

Keep in mind that killing all bacteria is neither possible nor desirable. It makes some people squirm but my view is we and our houses and implements only need to be clean enough not perfectly clean. I have no use for antibacterial body wash or surface spray, mostly soap and water does just fine. You will note that doctors ask you to use full body wash the day before you go in for major surgery not every day.

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Useful info. Thank you for taking the time to post it for us.

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It is frightening to see ‘kills 99.9% germs’ because that means helpful natural flora micro-organisms are killed as well, It is like throwing the baby out with the bathwater. Natural defences are lost. Hand sanitizer should not completely replace thorough washing with soap and water. Mobile phones should be cleaned often, they carry huge numbers of bacteria.

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Just as a curiosity point, every time I see the “kills 99.9% of germs”, my mind, being somewhat weird, always wonders how long it would take the 0.1% to reproduce back up to the original number?

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There is movement in sales of cleansers to claim to be germicidal, the makers think that this is attractive to buyers, that the public for some reason wants to disinfect everything in sight. It looks to me that this has become exaggerated since COVID as the more fearful we become and the more the situation appears out of control the more we want quick fixes that we can initiate. Feeling in control is the next best thing to being in control.

You are right that nuking everything in your house and on your person with disinfectant is not useful and may be harmful in some situations. The makers of such products did not create the fear that supports that idea although they do play on it. You will see advertising campaigns showing young mothers doing “the right thing” and being good mothers protecting their brood by using these products.

The real source of the problem though is ignorance. We are brought up on the idea that all microbes are bad and must be eliminated. So much for fermented beverages, many milk products, kombucha, black tea, some cheeses, some pickles, etc etc.

As for teaching that we are walking around with thousands of species of microbes on our skins and in our guts that are highly beneficial, if that is taught in school it doesn’t seem to stick.

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Hand Sanitizers must have 71% alcohol to be effective. This concentration of alcohol and water can dehydrate the gram positive bacteria and gram negative bacteria, plus fungi and fungal spores. If the alcohol is 100% then there is no water present to dehydrate the bacterial cells. Another point gram positive bacteria produce spores that are highly resistant even to heat, eg Clostridium, but when the spore matures and forms the cell structure it is susceptible to 71% alcohol.

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For those who may ponder about the ability of water to dehydrate things it might be clearer to say that 100% alcohol does not cross the membrane as well as 70% and thus the organism may not be dehydrated.

However not all microorganisms are killed by 70% alcohol, bacterial spores and some microbes with resistant coatings survive. There is a growing trend for bacteria to become resistant to alcohol which can be a source of hospital-acquired infection.
To be clear 70% alcohol does kill coronavirus.

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Sorry, but 100% ethanol/alcohol is an extremely good dehydration agent. In fact, it’s used routinely in histology (the microscopic study of tissues), where tissues need to have all water removed before further processing for microscopy. I used to use it all the time, as a former histologist. In technical terms, it’s a fixative, although not one of the better ones, because it kills the cells while preserving (to a certain extent) their structure.

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In the context of extracting water from tissue it is. In the context of microbes that have a coating that needs to be crossed first it isn’t. In this thread we are talking about killing household germs not tissue slices going under a microscope.

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I have noted that people are saying that 70% etc is effective etc. It should always be stated whether it is 70% by volume 70%v/v or 70% by weight 70% w/v which is quite different.

The three measures you give are in fact different. The question is are they different enough to matter? The answer to that is it depends on what you are trying to kill and how long you are prepared to wash with the chosen sanitiser.

For example, the Choice review used a threshold of 60% w/w for adequacy and the USA CDC uses 60% for COVID. Take a contrary example Balnea Instant Hand Sanitiser the Woolies home brand does not specify the content at all on the bottle and I cannot find the details anywhere, yet it is one that claims “kills 99.9%” so you wouldn’t know.

As mentioned above the 99.9% claim is too vague to test without more detail.

Do you have a specific example in mind, have you been caught out by some product that claimed a certain content?

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