What "Kills 99.9% of germs" really means


Shocker: Advertising health claims are often misleading. In this case, it looks like most of the products that tout near-perfect germ-killing abilities are getting those results in trials that aren't exactly designed to mimic real-world conditions. When a University of Ottawa microbiologist ran a more realistic demonstration for Canadian schoolchildren, he turned up VERY different results.

Three popular sanitizers killed between 46% and 60% of microbes on the students' hands, far short of 99.99%. Bugs that aren't killed by sanitizers aren't necessarily more dangerous than those that are. But the more that remain, the greater the chance of infection, doctors say.

The ad writers also benefit from regulations that allow them to claim 99.9% effectiveness without actually killing 99.9% of all germs, all the time. Instead, representative samples can stand in, and there's room for do-overs in the lab, if the first test doesn't work.

Wall Street Journal: Kills 99.9% of Germs—Sometimes

Image courtesy Flickr user If you dream it..., via CC


    1. Yes. Basically, insane clean doesn’t exist outside the lab. Don’t buy the hype. (And, frankly, you don’t really need–or want–insane clean most of the time anyway.)

  1. Come on, this sanitation craziness is stupid anyway.

    The immune system needs some training and occupation to work properly.

    Germs on hands rarely kill anyone. The world isn’t full of bubonic plague bacteria.

    1. I must attest to the fact. I have Crohn’s disease[URL=”http://blog.autoimmunetherapies.com/necator-americanus-superfriend/”]I have Crohn’s disease[/URL]
      , an auto immune disorder, probably the result of an immune system confused by the lack of germs and dirt in my childhood.


  2. What many people do not know is that you need the alcohol based hand sanitizer AND when you apply it, you need to glop it on at least the size of a quarter. The stuff needs to coat your whole hand for it to be effective.

  3. Actually, I’m relieved to see this. Can you imagine the super-race of bacteria that would develop of only the strongest most antiseptic-resistant 0.1% survived to reproduce?

  4. According to some experts, germs are actually good for you, because without exposure to them the body’s immune system would be weaker. Ever noticed that toddlers tend to put everything within arm’s reach into their mouths? Some research has suggested that this behavior functions to build up the body’s defenses.

  5. I think it is pretty well established that most of the germ removal is from rubbing, not the liquid, in either alcohol or soap and water-based cleaning. You are really removing the germs not killing them. Alcohol does kill some by itself, but the nice thing about alcohol is that it evaporates so it is ideal for a handy-on-the-go hand cleaner.

  6. the 0.1% that survive aren’t necessarily tougher, may just reside in protected places like under your fingernails, in fleshy folds, etc.

    And as was said before, just wash well with soap. Do it regularly but not OCD regularly ;)
    And if you need insane clean, then learn how to wash your hands properly (clean room quality, not surgery quality), dry your hands afterwards with single use paper towels by patting the moisture off (not rubbing), and then apply hand disinfectant gel and let it dry.
    You’re almost surgically clean, and way clean enough for any sensitive task. I’ve worked both in a hospital and in pharmaceutical manufacturing, this is the correct way.

  7. I knew intuitively that the 99.9% claim was marketing baloney, but it’s nice to have the confirmation.

    @9 and 10- very true. Some scientists have been raising that very point in commentary on antimicrobial products. Additionally, there’s not a heckuva lot of evidence that these products are actually having an effect on infection rates. I think Dr. Weiss’ point is a good one: I think the public’s awareness of appropriate anti-infection hygiene is very low, and it’s quite possible these sorts of products encourage people to think they can buy a simple substitute for hygiene.

    Think about how many people you encounter who walk out of the restroom without even a hand-rinse; blow their nose or sneeze and go right back to serving food & drinks; put their hands all over bannisters or counters and then touch their faces; “wash their hands” with a cursory 8-second soap-and-rinse. People don’t even think about this stuff, which is why the CDC and other groups spend so much time and effort putting up signs and advisories when flu season comes around.

  8. Individual microbes that survive aren’t necessarily tougher, but they’re certainly more likely to be tougher, and that’s all evolution needs. Even if, say. 99.99% of the selection is just random. Hospital superbugs are a result of this.

    Yup, evolution is annoying.

  9. I’m sure someone mentioned it but some bugs can reproduce like 9999 to the third power in a mater of a few hours.

    Everytime I go for my routine check up at the dentist I ask if there is a cure for cavities. The dentist always jokes “yes brushing”. After probing for a real answer he tells me the microbes that cause cavities also control microbes that could do much more damage but he’s sketchy on the details. After all cavities is their business :) And It’s not the bacteria that causes cavities it’s their poop. I know that certain bacteria are passed down via mom and some cause greater chances of cavities. Just some thoughts.

  10. None of you has ever actually seen a person die from an infection, have you? Or go blind? Or become paralyzed?

  11. 99.9% really means population reduction, not an actual “kill”. To truly disinfect something, a different method must be applied, be it heat, radiation or other chemicals you really don;t want on your skin. Yet, then again, depending on the organism, one method is more effective than others.

    If we are talking about pyrogens (organisms that will give you a fever), dry heat (220F) is the way to go to achieve 99.9%+ organism population reduction.

    That or Chuck Norris, because antibacterial soap may only kills 99.9%, but Chuck Norris kills 100% of whatever he sets his mind on.

  12. So does that mean we don’t have to worry about super bugs? If we aren’t actually killing everything that can be killed by current technology, than are super bugs even being bred?

  13. Hey numbers 17 and 21 – I actually do disinfection experiments an an EPA-funded project. Basically, the 99.99% reduction comes from the EPA rules that say if a disinfectant is successful, there must be a 4-log reduction in virus titer. So you can start with say 6 logs of virus or bacteria, and as long as you go from 1 million bacteria down to below 100 bacteria, you have 4 logs and you meet the disinfection criteria. You aren’t necessarily driving evolution, disinfectants are chemicals, not antibiotics. Yes, in some rare cases bacteria with stronger cell walls might be selected for, but most of the time they already exist in nature anyway, and plain old soap selects for them. Viruses, on the other hand, which is what most ethanol gel products claim to kill 99.99%, do not drive viruses to be “stronger” in any way. It either kills them or it doesn’t. Some virus might survive just because the active agent in the disinfectant is “used up” by killing the other 99.99%. However, it is more likely that the disinfectant killed more than 99.99%, but it is only reported at that because that is the EPA’s approved disinfectant gap. We routinely knock 7 logs of viruses down to undetectable levels with basic chemicals like bleach or citric acid, but they will be reported as a 4-log kill.

    Keep in mind that in the wild on the surfaces of your bathroom sink or toilet, there are not millions of viruses or bacteria lying around waiting to attack you. So as long as there are less than 10,000 infectious particles or bacteria on the surface, the chemical should kill all of it when used as directed.

  14. And one more thing – most hand sanitizers say they kill VIRUSES, not bacteria. In order to test for an unknown virus, this guy would have have to have spent alot of money looking for a hell of alot of viruses by plating the swabs on lots of different types of cell cultures. It would be FAR easier to just plate the swabs on bacterial media plates and see what grew, likely alot of staph and strep that we have on our bodies all the time. And those bacteria are not going to be anywhere near as susceptible to disinfection by ethanol-based hand sanitizers as viruses are. Most viruses are extremely fragile relative to bacteria. A few that are non-enveloped, like adenoviruses, picornaviruses and noroviruses are extremely resistant to soap, so perhaps this is what he is looking for. But that would be stacking the deck, since I don’t see any hand sanitizers claiming to kill these.

    I would be interested in seeing the actual data from this, since the WSJ does not report the agents that were recovered. A pubmed search on the Tetro, J brings up bacteria and virus work, so perhaps it is both. When it gets published, I suppose we shall see.

  15. Advertisers lie or distort the truth? No…I’m going to have to rethink some basic principles.

    Actually, these hyper-disinfect-your-house ads tend to make me want to roll in mud for a while, just to be as far away from their sterile futuristic lifelessness as possible…

    1. Me too.

      An Ad campaign I vaguely remember claimed ‘kills 99% of known germs’. Thereby not killing any of the resistant one percent of known types of ‘germ’, and not killing unknown germs at all.

  16. Water kills 99.9% of all people if you hold them under long enough, that doesn’t mean a rainy day is going to wipe out the species.

  17. MY BAD! I was looking at an old bottle of Purell which stated it killed 99.99% of the flu virus (easy to kill).

    I just found a new bottle of Target generic instant hand sanitizer gel and it says it “kills 99% of germs without water.”

    But reading the back of the bottle it says in the Uses section that it “decreases bacteria on the skin that could cause disease”. It goes on to say “Effective at eliminating over 99.99% of many common harmful germs and bacteria in as little as 15 seconds.”

    I agree. There is much bogosity in these here claims. I wish I could get away with those kid of statements, my lab work would be finished already…

  18. My mother is a nurse and according to her, a proper washing of hands requires THIRTY SECONDS of lathering.

    I generally only indulge in that when I’ve been out shopping and in contact with a lot of surfaces, because I wash my hands so much at work (for non personal safty purposes- I am a printer and the presses are dirty but the paper must be clean so I wash my hands with pumice soap at least once an hour.)

    I’ve always thought the fear of germs-from-surfaces was a bit overblown. Keep your fingers out of your mouth and eyes and you should be fine.

  19. I always thought that the word ‘germ’ was evasive marketing-speak that allowed the ad guys to claim anything they liked, and didn’t map to anything real like virii or bacteria or protozoa or anything!

    Is there any legitimacy to it?

  20. Even if the claims were true, they’re stupid. There are millions of “germs” on your skin. If you kill 99.9% of them, that means you’ve left thousands of them on your body to reproduce without competition, and these are the ones that ARE RESISTANT to the cleanser.

    So the claims could have been true once upon a time, but now the vast majority of microbes will have built up immunity.

  21. The elementary school where I work installed hand sanitizing stations for the kids. The material is in 1 L bags of 70% Ethanol. As much alcohol as a quart of 151 rum. I tested some. It tastes awful and burns like gang busters. I ordered a MSDS for it to see if it was safe to store. Instructions after handling: Wash Hands.

  22. Yogurt makers claim their products contains good bacteria that is good for your stomach. How about a hand wash that contains good bacteria for your hands?

  23. Gee, I am so sick of this national fear epidemic. My GF is getting her little daughter a GERM doll for christmas, it comes with a bottle of hand sanitiser.

    I was introduced to a friends wife last night and she wouldn’t shake my hand, yep you guessed it, I got fisted!
    She called it a “winter handshake”, oh gag.

  24. Your skin is home to good bacteria, too. Sanitizing too much will actually decrease your immune system, as it kills your skin’s natural defensive bacteria. Wash your hands every so often, and avoid touching your face. If you think that you may have been exposed to a bug, remember this: all viruses have gestation periods. If it can’t gestate, it can’t hurt you. Most of the time, invaders gestate in the mucus in your throat and nose, so keeping your nose snot-free and (this is gross) coughing up or swallowing mucus will keep you from getting sick. Almost nothing can survive in your stomach acid. I recommend Neti pots for the nose cleaning (if you can handle it). I can’t, so I just blow my nose really well in the shower.

  25. id like to take this opportunity to thank all the antibiotic hand wash companies and people who use their products religiously. thanks to you we dont have to worry about little old staph infections, we just have to worry about losing a limb from necrosis caused by mrsa

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