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Why is 70% isopropyl alcohol a better disinfectant than 99% isopropanol?
- TomMarius 6y agoI am not sure if this is the case, but disinfectant that is too aggressive will slowly but surely destroy your skin's top layers.
- pitaj 6y agoThe top layers of skin are already dead though. You're much more likely to break them down while washing your hands.
- masklinn 6y agoThey don't destroy the cells themselves, but they wash away oils and significantly dry the skin, quickly leading to skin irritation and potentially cracking. This is why hand sanitiser usually have some sort of moisturiser as part of the solution, and why if you wash your hand a lot you'll quickly get irritations and worse if yon don't also moisturise them regularly.
- jszymborski 6y agoThis is why you shouldn't just be dousing your hands in EtOH/IPA regularly, even if it's 70%. Either use hand sanitizers that have e.g. ethylene glycol to simultaneously moisturize and protect your dermis, or use latex/nitrile gloves when handling dangerous things, sterilize those with alcohol, and wash your hands with hand soap.
- blattimwind 6y agoI would have thought the fact that splashing IPA over your skin makes it turn white-ish and gives it a weird texture should be a pretty big pointer for people to not do that but I guess people are people.
- masklinn 6y ago> Either use hand sanitizers that have e.g. ethylene glycol to simultaneously moisturize and protect your dermis Ethylene glycol is a dessicant, and moderately toxic. You really don't want to add that to hand sanitiser, or to rub ethylene glycol on your skin after 70% alcohol as a moisturiser. You might be thinking about polyethlylene glycol. Or possibly glycerol (a humectant and moisturiser) but that's less likely.
- jszymborski 6y agoMy bad, I was definitely thinking of Caprylyl Glycol!
- amelius 6y agoIsn't the skin rebuilding itself every [small number] days? Is the alcohol interfering with this process? Does it have an irreversible effect?
- TomMarius 6y agoSkin also contains oils etc that have a part in the correct and healthy functioning.
- prmph 6y agoI fear I may have done this to my hands out of ignorance; after frequently assaulting them with alcohol-based sanitizer and dishwashing soap while on lockdown, they now get pruney very quickly when they come in contact with water. Is this situation irreversible?
- projektfu 6y agoWith moisturizers, somewhat. The best hand sanitizers (Avagard, for example) are good at preserving the skin texture. The lipids can be replaced with typical moisturizing lotions. Dish soap is probably not more effective than Dove soap, so use milder soap.
- adrianN 6y agoNo, skin is regenerated regularly. You need to destroy it pretty deeply to permanently disrupt this mechanism.
- jszymborski 6y agoWhat's been working for me has been keeping a bottle of skin lotion (Lubriderm has been working well) next to the sink. I wash my hands, dry thoroughly, and apply lotion. I do this at every washing, to assure that my skin is protected after all the oils are stripped by the detergent. I'm not a dermatologist, however, so consult a medical professional if problems persist.
- mthoodlum 6y ago"The presence of water is a crucial factor in destroying or inhibiting the growth of pathogenic microorganisms with isopropyl alcohol. Water acts as a catalyst and plays a key role in denaturing the proteins of vegetative cell membranes. 70% IPA solutions penetrate the cell wall more completely which permeates the entire cell, coagulates all proteins, and therefore the microorganism dies. Extra water content slows evaporation, therefore increasing surface contact time and enhancing effectiveness. Isopropyl alcohol concentrations over 91% coagulate proteins instantly. Consequently, a protective layer is created which protects other proteins from further coagulation." Many viruses have a hydrophilic outer membrane and the water helps the alcohol to penetrate the virus.
- nodesocket 6y agoThank you, I immediately hit back when I saw how long that article was.
- PostOnce 6y agoThe second sub-heading asks the question, and answers it in the first paragraph, so you can gain the answer without reading the entire article; if it grips you, then you can keep reading.
- penguin_booze 6y agoI relate with you. I wish articles also published a TLDR version. Personally, I've trouble focusing if the content is less engaging, or am there just to know the gist. I suspect I've ADD-like traits - when I see an article beginning like "it was a warm sunny day in...", I say, "OK, maybe later". I however do appreciate long read articles have their place. So far I've noticed only Business Insider does this on their articles.
- debian3 6y ago« It was a warm sunny day in... » and i saw your comment on ADD, i was thinking it’s not really how or it works. It’s that you can’t focus on what your are reading. You start thinking about something else while reading and you don’t even notice it. « ...the end. » damn it. Let’s read it again « It was a warm sunny day in... » and I’m telling you it’s the worst thing ever because you can’t control it, no matter how hard you tell yourself I need to focus on it. It’s not a conscious decision to procrastinate. « ... the end. » Shit, again? At least that’s how it is for me.
- jszymborski 6y agoThe explanation I was always given when taking my biohazard/biosafety courses was that concentrations of EtOH or IPA greater than 70% evaporated too quickly to have the contact time you needed to sterilize e.g. work surfaces or (even worse) your gloved hand. Apparently here they mention that higher conc. of water make it a better solvent... which I buy, but alcohols still aren't the worst solvent for e.g. hydrophillic membranes, so I think other factors like contact time are likely in play.
- lifeisstillgood 6y agoThe interesting one is solutions >91% - they kill cells immediately- but this coagulates the cell proteins forming a protective layer - dropping time to disinfect from ten seconds to over two hours. It's fascinating how deep one can dive in any subject and still produce useful actionable insights :-)
- thatcat 6y agoYea, I mean that is crucial information for using the product. You would think they would explain some of this on the bottle.
- jcims 6y agoI wonder if they call this passivation like they do in chemistry - https://youtu.be/2yE7v4wkuZU?t=394 https://youtu.be/2yE7v4wkuZU?t=394
- hanniabu 6y agoIf you feel dumb it means you're learning
- selimthegrim 6y agoAnd here I thought the 'acid to water' rule was only so you would have water splashing instead of acid. TIL (and I was a chemistry undergrad)
- lonelappde 6y agoWhat do you mean? How does the order of adding ingredients influence passivation? You should create an acid water mixture before adding the mixture to another chemical.
- selimthegrim 6y ago"Do what you oughta, alway add acid to water" instead of water to acid is a safety mantra taught in high school and undergrad chemistry labs. You are correct but if you add the water to acid in the situation they'd shown the acid would be too concentrated as well.
- mslack616 6y agoWow... I used to watch a youtuber clean his tools with a bottle labeled as "Isopropyl Alcohol, AKA IPA" I always thought he was making fun of IPAs as in the beer style. I feel so dumb hahaha x_x
- smnrchrds 6y agoWait until you hear about International Phonetic Alphabet.
- gumby 6y agoWe need to expand the TLA space. The only options I can think of are increasIng the number of letters and redefining “T” to “tetra” or even “thirty”. Time to get started on a new RFC
- stickfigure 6y agoPerhaps consider a FLAX? Four letter acronym, experimental.
- gumby 6y agoThat will only work until the RFC is approved, at which time the X will be dropped.
- mkr-hn 6y agoYou can never have too many The Last Airbender spinoffs.
- foolmeonce 6y agoI guess I'm still not getting TLA, since my Temporal Logic of Actions model says there should only be 17 valid spinoff states.
- Sharlin 6y agoETLAs got you covered: https://wiki.c2.com/?ExtendedThreeLetterAcronym https://wiki.c2.com/?ExtendedThreeLetterAcronym Although I'd like to see something like XTLAs, for eXtensible Three Letter Acronyms.
- senectus1 6y agoWhy water is so "sticky" is a very interesting subject https://www.exploratorium.edu/ronh/bubbles/sticky_water.html https://www.exploratorium.edu/ronh/bubbles/sticky_water.html
- jcims 6y agoI think our personal every day experience with water dulls the intrigue around one of the more remarkable and unique substances on the planet.
- dylan604 6y agoMy favorite is Ultrapure Water (UPW) [0]. It's so pure, that it is used a a stringent. I watched video about one of those underground subatomic particle experiments where they use UPW. One of the technicians accidentally let his hair get wet, and it immediately "bleached" his hair. [0]https://en.wikipedia.org/wiki/Ultrapure_water https://en.wikipedia.org/wiki/Ultrapure_water
- azinman2 6y agoI don’t understand why it would bleach the hair? Theoretically couldn’t you drink this? It’s just water that’s free of contaminates like viruses, bacteria, etc?
- wombatpm 6y agoUltra pure water generates a very strong osmotic gradient in that it will simultaneously explode cells as the pure water rushes in to reduce particle count inside a cell while at the same time drawing out any free particles. Another way to think about it is that UPW is an acid with a concentration of 55 Moles/liter.
- ivalm 6y agoStringent just means something is strict, as in the standards for making UPW. Nothing is “used as a stringent.” UPW also doesn’t immediately bleach hair, it would have to be a pretty prolonged heavy stream. Mostly UPW is pain in the ass because it corrodes metallic pipes, but is pretty harmless to people unless you really have massive amounts. One of the reasons it’s harmless is because the moment it touches you it isn’t really ultra pure anymore, it really takes parts per million to become not UPW.
- ck2 6y agoyeah but here's the thing, is that bottle of alcohol made in china actually 70% or did they decide to save 5% costs even usa is not immune to corner cutting, there's no government oversight or inspection, everything is defunded or regulations completely eliminated
- steve_adams_86 6y agoWhen it comes to medical solutions I'd think it's more than frowned upon to mislabel things... I've had some bad products from China (and many other places) but largely in consumer spaces where people won't care too much and consequences aren't significant. When it comes to lab or medical equipment, does this practice actually occur? It completely defeats the intent and would lead to a total loss of business, wouldn't it?
- blub 6y agoWestern companies check the wares they import, or at least that's the idea. Buying directly from China is a fool's errand. The EU is finding a shocking amount of dangerous substances in China imports.
- alexbanks 6y agoTrying to steer a conversation about science into a conversation about politics. Stay classy.
- rootusrootus 6y ago> there's no government oversight or inspection Aside from the FDA and the TTB, you mean.
- coronadisaster 6y agoThey don't even have the resources to check the food supply in the US... olive oil, fish, are often not what they claim. So that would not surprise me.
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- cashsterling 6y agoAt work, we already use technical grade 99.8+% IPA for various things and have a bunch on hand. so we have been prep'ing 70% with RO water and wiping down high touch surfaces. 70% IPA in water is the go-to cleaning/sanitizing agent for most pharmaceutical cleanrooms. They also use other agents, 0.2-0.5% bleach, low pH cleaners, peroxides, etc... but IPa is the mainstay.
- StavrosK 6y agoAlso, why does alcohol easily kill microorganisms but doesn't destroy skin cells?
- compsciphd 6y agoouter skins cells are already dead....
- oliveshell 6y agoAlso, alcohol will certainly leave your hands dry and cracked given prolonged contact. (I used to refurbish old PCs and we used isopropyl alcohol liberally as a cleaner.)
- masklinn 6y ago> Also, alcohol will certainly leave your hands dry and cracked given prolonged contact. Indeed, alcohol will dry the hell out of the skin, which is why alcoholic hand sanitiser have some sort of moisturiser included (e.g. glycerol).
- rootusrootus 6y agoAnd sanitizers are usually mostly ethyl alcohol, for the same reason.
- Wistar 6y agoEven with the moisturizer, hand sanitizer will cause my knuckles to become so chapped they cracked and bled within a few days with just a few applications per day. I had to stop using it as I began to fear infection.
- masklinn 6y agoYes, the moisturiser mitigates the issue but will not solve it. If you need to sanitise your hands a lot and they’re sensitive you may want to use or switch to disposable gloves.
- elsjaako 6y agoCan someone link to a study that shows this is the case for virusses also? The example listed in the article, Staphylococcus Aureus, is a species of bacteria. Last time I had this discussion they linked to a study that said that for viruses, higher concentrations are better. (Epidemiologic Background of Hand Hygiene and Evaluation of the Most Important Agents for Scrubs and Rubs Günter Kampf and Axel Kramer)
- giarc 6y agoLikely depends on the type of virus. There are two types, enveloped and non enveloped. The enveloped would likely act similar to bacteria whereas the non-enveloped would likely suffer more from higher concentrations of alcohol.
- EForEndeavour 6y agoAnd the coronavirus is enveloped. https://theconversation.com/vodka-wont-protect-you-from-coronavirus-and-4-other-things-to-know-about-hand-sanitizer-133593 https://theconversation.com/vodka-wont-protect-you-from-coro...
- draugadrotten 6y agoand soap is both sufficient and great at destroying the coronavirus. https://www.engineering.com/DesignerEdge/DesignerEdgeArticles/ArticleID/20146/A-History-of-ViolenceHow-Soap-Attacks-a-Coronavirus.aspx https://www.engineering.com/DesignerEdge/DesignerEdgeArticle...
- elsjaako 6y agoDo you happen to know of any peer-reviewed sources stating this? Up to now I've not been able to find any.
- achillesheels 6y agoI’m working on a nebulized ethyl alcohol biocidal therapy for SARS-CoV-2 and had to research this (plz see my Twitter for a chronology @jhazani). I’m disappointed the link abstracts the actual mechanism of action, other than a hypothesis that evaporation time and contact time makes a difference. It still does not explain distinctly the effects of contact time, which principally involves the polarity of alcohol which disrupts the viral envelope and “denatures” proteins according to the CDC [1] and their arcane reference text you can only find in a medical school library [2]. In other words, the hypothesis is there is electrostatic attractive forces that rip the buggers apart, in which this “pressure” is quantitatively stronger in the presence of molecular hydrogen bonding, ie greater dipole moments between the aqueous solution and the virus. (PS our study design will rely on 200 proof absolute ethanol for go-to market simplicity and for lowest surface tension deposition into the alveolar pulmonary region to promote alveolar stability) [1] https://www.cdc.gov/infectioncontrol/guidelines/disinfection/disinfection-methods/chemical.html https://www.cdc.gov/infectioncontrol/guidelines/disinfection... [2] Ali Y, Dolan MJ, Fendler EJ, Larson EL. Alcohols. In: Block SS, ed. Disinfection, sterilization, and preservation. Philadelphia: Lippincott Williams & Wilkins, 2001:229-54.
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- azinman2 6y agoIf I have a 91% currently, can I just add water to dilute it? Do I need some kind of special water vs what’s from my tap?
- tldmanagement 6y agoIt’s preferable to used sterile distilled water or water that has been boiled according to the WHO. https://www.who.int/gpsc/5may/Guide_to_Local_Production.pdf https://www.who.int/gpsc/5may/Guide_to_Local_Production.pdf
- azinman2 6y agoThank you!
- deleted 6y ago[deleted]
- p1mrx 6y agoIf you mix cheap booze (e.g. 40% vodka) with 91% isopropyl, you can make a larger quantity of 70% sanitizer than you could with pure water. Mixing on a scale can be pretty confusing, though, because the percentages are (I think) by volume, and water and alcohol have different densities.
- mdturnerphys 6y agoIt can also be confusing if you check the volumes after mixing, since the water-alcohol interaction decreases the molecular spacing and the total volume. V_(water + alcohol) < V_water + V_alcohol. https://en.wikipedia.org/wiki/Alcohol_by_volume#Volume_change https://en.wikipedia.org/wiki/Alcohol_by_volume#Volume_chang...
- hutzlibu 6y agoAny booze you buy has a huge tax on it, so you would be better of, with cleaning alcohol.
- noncoml 6y agoNot being able to clean my electronics from flux has been a collateral damage of Covid-19. I wish this article was more popular so people would stop hoarding 99% isopropyl.
- jki275 6y ago99% from electronics supply houses has been the only IPA available for a while. Newark had it in stock the other day, I bought some for my electronics work. The wife borrowed half a bottle to make her sanitizer with though lol.
- coronadisaster 6y agoI had more luck going to a small rural town
- chasd00 6y agothat's what I have been doing. I live in Dallas and head an hour or so East for items I know are going to be out of stock locally.
- coronadisaster 6y agoOne downside is that they dont take as much precautions in my experience.... Almost none had masks for example.
- alister 6y agoSince we're talking about counterintuitive things related to the coronavirus crisis, I was surprised to learn that N95 masks, that remove 95% of particles of size 0.3 μm, are even more efficient with smaller particle sizes. In turns out that 0.3 μm is the hardest particle size to filter--they call it the most penetrating particle size--hence filter testing is done at this worst-case size. The reason is that filters work due to several mechanisms which dominate at different particle sizes according to a curve: "For very small particles, less than 0.1 μm in diameter, the primary filtration mechanism is diffusion and the filter is very efficient. For particles between approximately 0.1 and 0.4 μm the filter is less efficient as the particles are too large for a great diffusion effect and too small for a large interception effect. Particles above approximately 0.4 μm enter the region where interception along with inertial impaction are predominant and the filter is very efficient again."[1] So if your filter is 95% efficient at 0.3 μm, it's even better at bigger and smaller sizes. The SARS-CoV-2 virus is 0.05 to 0.2 μm in diameter, so an N95 mask will be substantially better than 95% for coronavirus. [1] https://www.tsi.com/getmedia/4982cf03-ea99-4d0f-a660-42b24aedba14/ITI-041-A4?ext=.pdf https://www.tsi.com/getmedia/4982cf03-ea99-4d0f-a660-42b24ae...
- whatever1 6y agoSame reason that we care about the concentration of PM2.5 particles in the atmosphere. Once we inhale them they manage to reach the very end of our lungs.
- EForEndeavour 6y agoIs it? That's different from the counterintuitive N95 filtration efficacy. PM2.5 designates particles of diameter 2.5 microns and smaller, and I've read nothing that implies particles smaller than 2.5 microns are somehow easier for the respiratory tract to keep out of the lungs. The graph of filtration efficacy as a function of particle size is U-shaped for N95 masks, but not for the human respiratory tract.
- henvic 6y agoYou might find it interesting to know too that HEPA filters get more effective as they approach end-of-life.
- diebeforei485 6y agoAt first glance, I thought they were comparing two different chemicals. To minimize confusion, the title could be changed to: Why Is 70% Isopropyl Alcohol (IPA) a Better Disinfectant Than 99% IPA?
- tgsovlerkhgsel 6y agoFor me, the site only shows a multi-step hCaptcha. I solved it the first time, then the page reloaded and showed me the second one, which after two puzzles told me to try again.
- robbrown451 6y agoMy understanding is that soap and water is even better for coronavirus. Not just to wash it away, but to actually destroy is because it has a very fragile lipid layer.
- remote_phone 6y agoIt’s not even better. Washing with soap and water is effective but rubbing alcohol (Both 70% and 99%) takes seconds to kill coronavirus. It is almost instantaneous in terms of effectiveness. Soap and water take a few mins to reach the same level of effect as rubbing alcohol. There was a recent study by Stanford that measured the effectiveness of various cleaning methods.
- gojomo 6y agoPer the article, which seems thorough & authoritative, calling 73%-100% isopropyl alcohol solutions ‘rubbing alcohol’ is a misnomer. (This was news to me, but seems a precision important to respect when making hygienic recommendations.)
- robbrown451 6y agoThat's not what I get from these articles, which say it takes 30 seconds for alcohol to kill it (on surfaces), while soap and water (with scrubbing) will do the trick with 20 seconds. https://www.uchealth.org/today/why-soap-and-water-work-better-than-hand-sanitizer-to-remove-the-coronavirus/ https://www.uchealth.org/today/why-soap-and-water-work-bette... https://www.uchealth.org/today/ins-and-outs-of-disinfecting-coronavirus/ https://www.uchealth.org/today/ins-and-outs-of-disinfecting-... https://www.marketwatch.com/story/deadly-viruses-are-no-match-for-plain-old-soap-heres-the-science-behind-it-2020-03-08 https://www.marketwatch.com/story/deadly-viruses-are-no-matc... If you've got a better reference I'd be interested in seeing it, but this is what I've found.
- remote_phone 6y agohttps://www.thelancet.com/cms/10.1016/S2666-5247(20)30003-3/attachment/bfda5654-ca06-42d3-8beb-5f3aa5fc2df0/mmc1.pdf https://www.thelancet.com/cms/10.1016/S2666-5247(20)30003-3/... Table C lists the various disinfectants they tried including ethanol at 70%. All of them found undetectable levels of SARS-CoV-2 after 5 mins except hand soap, which took between 5 mins and 15 mins. I was off in my recollection that the study showed that alcohol killed the virus immediately. I may have confused that with a press conference several weeks ago but that data is probably suspect. All we know is that within 5 mins alcohol killed it to undetectable levels. Also note that the 20 second rule has never been tested. There is some value in washing in a sink with running water since it is physically removing the virus off your hands. And it’s been socialized that is will work in general for bacteria but no one has actually tested to see if 20 seconds of hand washing with soap will clean you of coronavirus specifically. The study above actually tested for coronavirus although I don’t think the soap test was for running water.
- aaron695 6y agoWhat does it mean for viruses? Covid-19 is number one issue...then let's work down. This matters because we need to keep it simple. If you run around telling people 99% is bad for C19 when it isn't, you are ruining peoples solutions when you don't have to. Sorry but these factoids are the fking issue. Telling people soap is better when hand sanitizer is clearly a better real world solution has caused lots of issues. Does 99% work worse on a virus like C19 by a significant amount?
- godelmachine 6y agoWhile we are discussing this, please don’t mind if I ask which is more effective - 70% ethyl alcohol vs 70% isopropyl alcohol? I am using the hand sanitizer by 3M which has 70% ethyl alcohol.