# Bacteria in the mouth **URL:** \ **Category:** Factual Questions\ **Created:** [December 22, 2002, 4:43am UTC](https://boards.straightdope.com/t/bacteria-in-the-mouth/144324 "2002-12-22T04:43:07Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![Jude](https://avatars.discourse-cdn.com/v4/letter/j/bc8723/32.png) [@Jude](https://boards.straightdope.com/u/Jude)\ **Post date:** [December 22, 2002, 4:43am UTC](https://boards.straightdope.com/t/bacteria-in-the-mouth/144324/1 "2002-12-22T04:43:07Z")
Are there any beneficial species of bacteria that live in the human mouth? In other words, does any of the bacteria living on my teeth help me digest my food or protect me in some way? Or is all bacteria in the mouth a nuisance? I use Listerine mouthwash, which is antiseptic, and I’m wondering if it’s such a good idea to kill all the living organisms in my mouth. Thanks. ---
**Author:** ![Ice\_Wolf](https://avatars.discourse-cdn.com/v4/letter/i/dfb087/32.png) [@Ice\_Wolf](https://boards.straightdope.com/u/Ice_Wolf)\ **Post date:** [December 22, 2002, 8:55am UTC](https://boards.straightdope.com/t/bacteria-in-the-mouth/144324/2 "2002-12-22T08:55:50Z")
According to [this site](http://www.stanford.edu/dept/news/report/news/december8/mouth-128.html) and others, there are way more beneficial or non-harmful bacteria in your mouth than there are harmful ones, **Jude**. I can’t find any cites for the negative aspects of using mouthwashes, but I’d still use mouthwashes in moderation. If most of the bacteria in the mouth are actually doing their job, why kill them right along with the “villains” unless something has gone drastically wrong? ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [December 22, 2002, 4:29pm UTC](https://boards.straightdope.com/t/bacteria-in-the-mouth/144324/3 "2002-12-22T16:29:03Z")
Use as much mouthwash as you want. You’ll never sterilize the mouth. The number of bacterial killed/removed by using mouthwash, brushing, etc. are not significant, and with the little bugger’s repro rates, they’re back up in population in an hour or two anyway. Plus your breath is minty fresh for at least a little bit. QtM, MD ---
**Author:** ![jenex](https://avatars.discourse-cdn.com/v4/letter/j/71e660/32.png) [@jenex](https://boards.straightdope.com/u/jenex)\ **Post date:** [December 22, 2002, 4:37pm UTC](https://boards.straightdope.com/t/bacteria-in-the-mouth/144324/4 "2002-12-22T16:37:55Z")
I believe it’s when the bacteria grow out of control that the problem starts. Just having a few thousand here and there is okay. That’s what a $200 microbiology class will get ya. ---
**Author:** ![MC\_Master\_of\_Ceremonies](https://avatars.discourse-cdn.com/v4/letter/m/bb73d2/32.png) [@MC\_Master\_of\_Ceremonies](https://boards.straightdope.com/u/MC_Master_of_Ceremonies)\ **Post date:** [December 22, 2002, 4:38pm UTC](https://boards.straightdope.com/t/bacteria-in-the-mouth/144324/5 "2002-12-22T16:38:38Z")
If IIRC bacteria makes up over half of a persons body mass. ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [December 22, 2002, 4:53pm UTC](https://boards.straightdope.com/t/bacteria-in-the-mouth/144324/6 "2002-12-22T16:53:12Z")
> [@](#): > > \*Originally posted by MC Master of Cermonies \* > \*\*If IIRC bacteria makes up over half of a persons body mass. \*\* You don’t recall correctly. ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [December 22, 2002, 4:56pm UTC](https://boards.straightdope.com/t/bacteria-in-the-mouth/144324/7 "2002-12-22T16:56:38Z")
To expand, the only place on people that bacteria live in significant numbers is on the body’s surface and and in the GI tract, along with the nasopharynx and ear canals. Women have bacteria living in the vagina, but it shouldn’t go further than the cervix. If you are particularly full of stool, it’s conceivable that you may have up to a pound of bacteria in your system, but that’s pretty much it. Even in morbid cases where the peritoneum is filled with pus, the bacterial weight is trivial compared to the weight of the white cells and body fluids. QtM, MD ---
**Author:** ![Rysdad](https://avatars.discourse-cdn.com/v4/letter/r/7cd45c/32.png) [@Rysdad](https://boards.straightdope.com/u/Rysdad)\ **Post date:** [December 22, 2002, 5:54pm UTC](https://boards.straightdope.com/t/bacteria-in-the-mouth/144324/8 "2002-12-22T17:54:51Z")
> [@](#): > > \*Originally posted by MC Master of Cermonies \* > \*\*If IIRC bacteria makes up over half of a persons body mass. \*\* He didn’t say a _live_ person. ---
**Author:** ![dqa](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dqa](https://boards.straightdope.com/u/dqa)\ **Post date:** [December 22, 2002, 6:02pm UTC](https://boards.straightdope.com/t/bacteria-in-the-mouth/144324/9 "2002-12-22T18:02:45Z")
In another [thread](http://boards.straightdope.com/sdmb/showthread.php?s=&threadid=130925), it was pointed out that even fecal matter is only 1/3 bacteria. The obvious follow-up question, By weight or volume? was never asked. Back to the OP, my dentist once suggested that repeated drying and irritation of the mucous membrane in the mouth by the alcohol in mouthwash could cause problems over a lifetime of repetitions. This was not something he was confident about, merely a possibility. His solution was to use ½ Listerine and ½ peroxide. Toothpaste with peroxide was not yet available. ---
**Author:** ![Enderw24](https://avatars.discourse-cdn.com/v4/letter/e/ba9def/32.png) [@Enderw24](https://boards.straightdope.com/u/Enderw24)\ **Post date:** [December 22, 2002, 6:29pm UTC](https://boards.straightdope.com/t/bacteria-in-the-mouth/144324/10 "2002-12-22T18:29:40Z")
OK, imagine this hypothetical: a person uses mouthwash for a good minute, twice a day, every day. How soon before they’ve created superbacteria where mouthwash doesn’t work anymore? In other words, can the long term effects of regular use be more harmful than short term minty freshness? ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [December 22, 2002, 6:57pm UTC](https://boards.straightdope.com/t/bacteria-in-the-mouth/144324/11 "2002-12-22T18:57:50Z")
It doesn’t tend to happen, **ender**. It would kinda be like our evolving resistance to being fire-bombed or being dropped in boiling acid rather than being poisoned. ---
**Author:** ![PosterChild](https://avatars.discourse-cdn.com/v4/letter/p/e274bd/32.png) [@PosterChild](https://boards.straightdope.com/u/PosterChild)\ **Post date:** [December 22, 2002, 7:44pm UTC](https://boards.straightdope.com/t/bacteria-in-the-mouth/144324/12 "2002-12-22T19:44:03Z")
**Qadgop** as usual has impecible answers. To add a tidbit- antibiotics are targeted (like poison)- they usually disrupt one or a few metabolic pathways (energy use, cell wall production, etc) which are more amenable to resistance by mutation. Mouthwash is like soaking them in alcohol which is much less targeted (like fire bombing or acid) and much less likely to result in resistance. PC ---
**Author:** ![KidCharlemagne](https://avatars.discourse-cdn.com/v4/letter/k/ed8c4c/32.png) [@KidCharlemagne](https://boards.straightdope.com/u/KidCharlemagne)\ **Post date:** [December 22, 2002, 7:55pm UTC](https://boards.straightdope.com/t/bacteria-in-the-mouth/144324/13 "2002-12-22T19:55:41Z")
While this isn’t a direct answer to your question: Don’t expect Listerine to keep your breath fresh for anything longer than 20 minutes. H20 and Peroxide is a better bet because not only will it kill germs but oxidize the food particles that they feed upon. ---
**Author:** ![MC\_Master\_of\_Ceremonies](https://avatars.discourse-cdn.com/v4/letter/m/bb73d2/32.png) [@MC\_Master\_of\_Ceremonies](https://boards.straightdope.com/u/MC_Master_of_Ceremonies)\ **Post date:** [December 22, 2002, 8:33pm UTC](https://boards.straightdope.com/t/bacteria-in-the-mouth/144324/14 "2002-12-22T20:33:41Z")
> [@](#): > > \*Originally posted by Qadgop the Mercotan \* > \*\*You don’t recall correctly. \*\* Obviously I’m not going to argue the point with an MD, but I do remember reading it in ‘some book’, were they perhaps being very liberal with their methods (maybe they only did on the basis of human cells vs bacteria cells) 😕