# How effective is alcohol in killing germs? **URL:** \ **Category:** Factual Questions\ **Created:** [August 20, 2001, 3:37pm UTC](https://boards.straightdope.com/t/how-effective-is-alcohol-in-killing-germs/77156 "2001-08-20T15:37:05Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![breaknrun](https://avatars.discourse-cdn.com/v4/letter/b/bbce88/32.png) [@breaknrun](https://boards.straightdope.com/u/breaknrun)\ **Post date:** [August 20, 2001, 3:37pm UTC](https://boards.straightdope.com/t/how-effective-is-alcohol-in-killing-germs/77156/1 "2001-08-20T15:37:05Z")
A SD search didn’t turn up anything. A search in google produced [this link](http://www.travdoc.com/articles/art28.html). Quoting from the above link: “Alcoholic beverages straight from the bottle are safe but it is a myth that alcohol kills the bacteria in ice cubes. (Alcohol does kill germs–but only after 24 hours, by which time I would presume the ice has melted!)” ``` I also found a few experiments which seem to show the effectiveness of alcohol inhibiting the growth of bacteria but not killing them outright. Why then do hospitals use alcohol swabs before administering shots and such? Are there other active ingredients in the swab besides alcohol? Related question: If alcohol takes so long to be effective, what would be a better alternative, chlorine bleach? iodine? ``` hydrogen peroxide? Which would be most effective at killing germs on household appliances and what would be best on wounds? I am guessing the answers would be different depending on use. Thanks. ---
**Author:** ![bibliophage](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bibliophage/32/7615_2.png) [@bibliophage](https://boards.straightdope.com/u/bibliophage)\ **Post date:** [August 20, 2001, 6:05pm UTC](https://boards.straightdope.com/t/how-effective-is-alcohol-in-killing-germs/77156/2 "2001-08-20T18:05:58Z")
> [@](#): > > \*Originally posted by breaknrun \* > \*\*Why then do hospitals use alcohol swabs before administering shots and such? \*\* The nurse who used to give me my allergy shots said it was to deaden the pain more than to kill bacteria. I don’t know if that’s true. ---
**Author:** ![cynic](https://avatars.discourse-cdn.com/v4/letter/c/e95f7d/32.png) [@cynic](https://boards.straightdope.com/u/cynic)\ **Post date:** [August 20, 2001, 6:47pm UTC](https://boards.straightdope.com/t/how-effective-is-alcohol-in-killing-germs/77156/3 "2001-08-20T18:47:33Z")
According to [www.childrenwithdiabetes.com](http://www.childrenwithdiabetes.com/dteam/1996-01/d_0d_10w.htm), alcohol is not a particularly effective antiseptic. I suspect that hospitals still use alcohol swabs at injection sites just to fulfill their patients’ expectations. ---
**Author:** ![gorewonfla](https://avatars.discourse-cdn.com/v4/letter/g/da6949/32.png) [@gorewonfla](https://boards.straightdope.com/u/gorewonfla)\ **Post date:** [August 20, 2001, 8:11pm UTC](https://boards.straightdope.com/t/how-effective-is-alcohol-in-killing-germs/77156/4 "2001-08-20T20:11:47Z")
Pre-Louis Pasteur alcholic drinks were the most popular not just because of the buzz, but because they were most healthy. Apparently part of the fermentation process prevents spoilage. ---
**Author:** ![easy\_e](https://avatars.discourse-cdn.com/v4/letter/e/eb8c5e/32.png) [@easy\_e](https://boards.straightdope.com/u/easy_e)\ **Post date:** [August 20, 2001, 10:38pm UTC](https://boards.straightdope.com/t/how-effective-is-alcohol-in-killing-germs/77156/5 "2001-08-20T22:38:42Z")
Any idea at what _concentration_ alcohol becomes an antiseptic? This is because I’ve worked in a couple labs that do cell culture. Part of sterile technique (to insure that you culture only the cells you want and not the bacteria/fungi/etc. floating around in the air) is to spray everything down with 70% alcohol before you put it into a laminar flow hood. It seems that this would be rather pointless if it didn’t do something. Granted, 70% is a lot more than most beverages (unless we’re talking about Bicardi 151). ---
**Author:** ![kniz](https://avatars.discourse-cdn.com/v4/letter/k/c37758/32.png) [@kniz](https://boards.straightdope.com/u/kniz)\ **Post date:** [August 20, 2001, 10:58pm UTC](https://boards.straightdope.com/t/how-effective-is-alcohol-in-killing-germs/77156/6 "2001-08-20T22:58:27Z")
There is some confusion here about the term “alcohol”. There is the kind of alcohol that I like to imbibe in and then there is the kind that is used for an antiseptic. **Grain alcohol** is for drinking and **Wood alcohol** is for swabbing. ---
**Author:** ![light\_strand](https://avatars.discourse-cdn.com/v4/letter/l/a6a055/32.png) [@light\_strand](https://boards.straightdope.com/u/light_strand)\ **Post date:** [August 20, 2001, 11:37pm UTC](https://boards.straightdope.com/t/how-effective-is-alcohol-in-killing-germs/77156/7 "2001-08-20T23:37:52Z")
Alcohol is indeed an effective antibacterial agent. It kills non-specifically by denaturing bacterial proteins, so it’s ideal for hospitals and labs because bacteria can not develop resistance as they can with targeted antibacterial agents like antibiotics. this site has more than would ever want to know about the efficacy of alcohol including those of iso vs etOH [http://www.slackinc.com/general/iche/stor0700/7ed.htm](http://www.slackinc.com/general/iche/stor0700/7ed.htm) **easy e** the site listed above also has a cite for the experiments that were done to show that the maximum efficacy for antibacterial use is at 50% to 70% **kniz** We use a 70% etOH as an antibacterial agent in my lab. However, most swabs are of isopropyl (rubbing) alcohol. We use a 98% etOH mixture for the HPLC because if it were any purer and we would need a liquor license (or so I was told when I ask why HPLC grade was only 98% pure). So technically you could drink the stuff except for the 2% mixtures of methanol and other impurities to keep the lushes away. So **breaknrun** my guess is that the low efficacy rates in the ice cubes is due to the low concentration of the alcohol. ---
**Author:** ![Patty\_O\_Furniture](https://avatars.discourse-cdn.com/v4/letter/p/96bed5/32.png) [@Patty\_O\_Furniture](https://boards.straightdope.com/u/Patty_O_Furniture)\ **Post date:** [August 20, 2001, 11:46pm UTC](https://boards.straightdope.com/t/how-effective-is-alcohol-in-killing-germs/77156/8 "2001-08-20T23:46:54Z")
From [UCSF Boilogical Safety Manual](http://www.ehs.ucsf.edu/Manuals/BSM/APPENDIX%20D.html): > [@](#): > > The disinfectant action of aliphatic alcohols increases with chain length up to 8-10 carbon atoms, above which its water solubility becomes too low. Ethanol and isopropanol are the most common alcohol disinfectants used and they are most effective in 50%-70% aqueous solution, with isopropanol being slightly more potent, less volatile and not subject to legal restrictions. They exhibit little activity against bacterial spores but are otherwise excellent and common laboratory disinfectants. Well if nothing else, the utilization of alcohol to swab the skin prior to injection will increase the index of refraction and thus make the vessels more visible at the skin surface. ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [August 21, 2001, 3:08am UTC](https://boards.straightdope.com/t/how-effective-is-alcohol-in-killing-germs/77156/9 "2001-08-21T03:08:50Z")
> [@](#): > > \*Originally posted by kniz \* > \*\*There is some confusion here about the term “alcohol”. There is the kind of alcohol that I like to imbibe in and then there is the kind that is used for an antiseptic. **Grain alcohol** is for drinking and **Wood alcohol** is for swabbing. \*\* Wood alcohol is a common name for methanol, CH3OH. Grain alcohol is good old ethanol, CH3CH2OH. “Rubbing” alcohol is isopropyl alcohol, CH3CHOHCH3. Isopropyl alcohol is what is commonly used as a topical antiseptic, not methanol. ---
**Author:** ![OcularGold](https://avatars.discourse-cdn.com/v4/letter/o/3e96dc/32.png) [@OcularGold](https://boards.straightdope.com/u/OcularGold)\ **Post date:** [August 21, 2001, 4:15am UTC](https://boards.straightdope.com/t/how-effective-is-alcohol-in-killing-germs/77156/10 "2001-08-21T04:15:05Z")
we use 95% ethanol in our lab for sterilization. > [@](#): > > if it were any purer and we would need a liquor license eh? i doubt that. we also have 100% ethanol. its used to dissolve certain materials that will eventually be ingested/taken in by living organisms (there cant be impurities thatll kill the plants/mice/whatever we’re working with). ---
**Author:** ![choosybeggar](https://avatars.discourse-cdn.com/v4/letter/c/8c91f0/32.png) [@choosybeggar](https://boards.straightdope.com/u/choosybeggar)\ **Post date:** [August 21, 2001, 10:17am UTC](https://boards.straightdope.com/t/how-effective-is-alcohol-in-killing-germs/77156/11 "2001-08-21T10:17:45Z")
[continuing EtOH purity hijack] We can get 95% EtOH or 100% EtOH from the stockroom. 95% is the highest purity achievable by simple fractional distillation (the remaining impurity being H2O). To make 100% EtOH, a quantity of benzene is added during distillation. Benzene combines with the water, and boils off as an azeotrope (sp?) at a temp below the boiling temp of EtOH. A small quantity of contaminating benzene remains in the 100% EtOH. Therefore, while 100% EtOH is preferable for certain applications, the 95% EtOH is what we use to spike the punch at our departmental holiday party.[/continuing EtOH purity hijack]