Some quick notes on hand hygiene

by willbradshaw2 min read6th Feb 202052 comments

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CoronavirusPractical
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I always wash my hands but typically not very well; I never worked in healthcare and never got trained. Given the current situation I decided to actually research how to do it properly.

Different sources differ slightly in their recommendations but the basic gist is the same. Some takeaways:

  • Washing your hands should take ~ 20-30 seconds. If it's taking you much less you're not doing it right.
  • Make sure you actually get all your hand surfaces, including your nails and between your fingers. The WHO guide has a good protocol that's probably worth memorising.
  • If possible, try to dry your hands with a single-use towel, or air-dry somehow; not much point washing your hands and then drying them on a dirty towel.
  • Good hand sanitiser (>60% alcohol) is a good substitute if your hands aren't visibly soiled, but you still have to do the all-surfaces routine and it should still take ~20 seconds.

For those of you who use Anki, ankifying this is probably among the most valuable things you could ever use it for. Especially in the early days of a maybe-pandemic! Ditto for those of you who use TAPs. My read of the various health authorities is that good, regular hand-washing is way ahead of gloves and masks in terms of keeping you and your loved ones safe.

Other things that now would be a good time to hammer into your head if (like me) you didn't already: coughing into your elbow, sanitising your doorknobs and light switches, and not touching your face. These are all a good idea anyway during flu season, but you should use the impetus of the current situation to actually do them , rather than just vaguely intending to learn how to do them like everyone else.


In the interests of reducing the number of people who read this, nod, vaguely intend to get better, and do nothing, here's an itemised checklist of concrete things you can do.

  1. Read the The WHO guide and memorise/Anki the hand-cleaning/sanitation. Here is a little minideck of cards I made for my own practice.
  2. Go to Walgreens/Boots/some other drug store and buy lots of little bottles of hand sanitiser (with alcohol!). Failing that, buy some big bottles off Amazon and aliquot them into smaller containers for use on the go.
  3. Order some alcohol in a spray bottle you can use to clean your light switches and doorknobs (I have no particular opinion on isopropanol vs ethanol for this, if somebody does then please comment and let me know).
  4. If you have trouble touching your face, order some of that anti-nail-biting stuff people use to train their kids and use it until your brain gets the message. Chili powder might work even better; if people try either of these (or something else) and it works well for kicking the habit I'd love to hear about it.

If anyone on here disagrees with any of this, please do comment and let me know. Other than the WHO, you can also find guidance from the CDC, the Mayo clinic and the NHS, among others. And here is some other guidance on staying safe in outbreaks (though note that the author's position on both gloves and masks is somewhat controversial).


ETA: Some more quick notes on when to wash/sterilise your hands. Broadly, the answer seems to be "much more often than you're probably doing it". Whenever you use the toilet, before you ever eat food, after touching dirty things, and after coughing/sneezing/blowing your nose are good TAPs to install (though note that you should not be coughing/sneezing into your hands). If you wash your hands super-often you're likely to have issues with your skin, but this is much less true of hand sanitiser, so use that to fill in the gaps.

This part is a little crude but probably important. I've previously gotten into a couple of arguments about whether you should always wash your hands after peeing, given that (i) your junk probably isn't that dirty and (ii) there's lots of things in your house / around town that are more dirty that you don't wash your hands after touching. I think argument (ii) is valid but more of an argument for cleaning your light switches/bathroom surfaces than for not washing your hands. It's also important to note that when you pee, and especially when you flush, you create a fine mist of very-much-not-clean toilet water that covers everything in the bathroom, including your hands.

But probably the strongest argument for always washing/sterilising your hands thoroughly after peeing is that you probably pee fairly regularly and don't wash your hands enough, and so instantiating a "wash your hands after peeing" TAP ensures you're washing your hands at least that often.

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What's missing for me here is a quantitative argument for why this is actually worth doing. Washing your hands more often would reduce risk, but is it actually worth the effort? (And for me there's also the problem that my doctor literally instructed me to wash my hands less often because of a skin infection thing.)

This seems like an easy thing to do a rough cut on.

Benefit:

" Adults average about 2 to 4 colds a year" - https://www.webmd.com/cold-and-flu/common_cold_overview

" People usually recover in seven to ten days" - https://en.wikipedia.org/wiki/Common_cold

Assume your productivity is halved (Mine is far worse, since ~90% of the value of my time is when I'm operating at peak, which I can't do at all when sick.)

"Handwashing can prevent 21% of respiratory sicknesses" - https://globalhandwashing.org/about-handwashing/why-handwashing/health/

So handwashing would save an average of 0.2*8.5*3*0.5=2.55‬ days of productivity.

Cost:

30 seconds per handwashing * 15 times per day * 365 days / 18 waking hours per day = 2.5 days of time.

So as long as you're completely neutral to the externality costs like making other people sick, don't mind the physical unpleasantness of getting sick, and there's no scary superbug going around, this seems like, well, a wash.

If you have kids, you'll get sick more, and washing has correspondingly higher benefits. And if you come into contact with the elderly, very young, or the otherwise sick, the externality costs are far higher, and you're a jerk for not doing this.

Bottom line: yes, it's only marginally beneficial. But if 2019-NCoV is at all worrying, it likely tips the balance. Now instead of arguing about the exact numbers here, i.e. justifying your inaction by explaining to the world why the costs are higher and the benefits are lower, go wash your hands.

I notice that you only compare time spent hand washing to time spent debilitated by respiratory illness, but hand washing also reduces likelihood of other ailments, eg gastric infections due to fecal or other bacterial contamination, and intestinal parasites (especially threadworm if you have kids...).

Even without specific numbers on the time that these might rob you of, hat would seem to push the balance in favour of hand washing.

Apart from anything else, being ill or having a high parasite load is just plain unpleasant, and long periods of illness (even if few and far between) are more damaging to sense of wellbeing than short periods spent on a menial task multiple times a day.

We should take into account the welfare of others, too. Besides protecting me from disease, washing my hands prevents me from transmitting it to someone else. It's pretty much analogous to vaccines.

Yes, it was a quick and in some ways worst case / pessimistic analysis.

Cool to see that they're in the same ballpark.

“Handwashing can prevent 21% of respiratory sicknesses”—https://globalhandwashing.org/about-handwashing/why-handwashing/health/

Do they say which conditions are being compared? Is it no handwashing at all vs 30 seconds 15 times per day, or something else? (I would look myself, but I can't find the quote with cmd-f.)

I'd guess that washing your hands has some diminishing marginal returns, so if washing your hands for 30 seconds 15 times a day is approximately as good as not washing your hands at all, you can probably do better than both by being somewhere in the middle (e.g. washing your hands for 20 seconds at the 10 points during the day when they're most dirty).

I'd guess that washing your hands has some diminishing marginal returns, so if washing your hands for 30 seconds 15 times a day is approximately as good as not washing your hands at all, you can probably do better than both by being somewhere in the middle (e.g. washing your hands for 20 seconds at the 10 points during the day when they're most dirty).

My personal guess would be that if you want to minimise the time cost of hand washing your best bet would be to really drill in (a) always washing your hands before touching food, and (b) not touching your face. If you can be very confident in those two things you can probably let up on the general hand hygiene slightly. I was going to say that this applies if you don't care that much about externalities, but to be honest if you always wash your hands before touching communal food you'd already be doing much better than most people.

(ETA: Also see David's other comment below)

You mean this one? Yeah, that does suggest that there are increasing marginal returns to time spent per hand-washing session, at the typical level of effort.

Good post. I would actually argue that the cost of many second activities is much lower than the cost of one block of seconds, because taking small breaks in between work isn't zero value.

I agree. It is very common for field experts and authorities to issue directives without considering the associated time costs, especially when these costs are small when measured relative to the relevant behavioral unit (e.g. 30 seconds per hand washing). If you consider each directive individually, it often seems that the benefits justify the costs. But when both costs and benefits are aggregated over time, a different, more pessimistic picture often emerges. I wash my hands ~10 times per day, and so invest ~30 hours per year on this habit. Is this sacrifice worth it? It isn't obvious to me that it is.

I am reminded of that satirical post where Rob Wiblin describes his "daily routine for maximum productivity", comprised of dozens of activities many of which seem individually worth doing. Clearly, however, the routine as a whole is a net waste of time, since it would require a large fraction of the day to complete, thereby decreasing productivity overall. This suggests that our "micro intuitions" aren't very reliable, and that we should check them by considering the big picture.

I don't have a long reply to this yet since I didn't get the chance to look up actual data (as opposed to recommendations) but I'd be interested to

Insofar as a health intervention is ineffective it could be for one of three reasons:

  • The base rate of the thing it prevents is low
  • The intervention is not good at preventing the thing
  • The thing is not that bad even when it does happen

Which is your main sticking point here?

I'm not sil ver, but as a casual coronavirus watcher (in part because I live significantly closer to affected areas than most), my instinctive doubts are mostly 1 and 3. What numbers are you using for those to base the claim "ankifying this is probably among the most valuable things you could ever use it for."?

Yep, as always context matters. Have you been doing something that puts stuff on you hands that is no already spread everywhere you are and will touch or for some reason has caused a significantly higher concentration on your hands versus the environment?

As the OP points out, after washing actions matter too. But it more than merely the act of drying your hands.

Last, to some extent your hands are well prepared to deal with a lot of stuff -- that is exactly what our skin evolved to too: protect our internals from the external. So a good part of the hygiene is also about just where you put your hands on your own body. Rub your eyes a lot? Perhaps better than washing would be using a clean tissue, then throw it away. Byte your fingernails, or stick you fingers, hands on/in you mouth a lot? Stop or be aware of what you've been touching since the last cleaning (were you just cutting up the raw chicken that you will cook for dinner?)

Have you been doing something that puts stuff on you hands that is no already spread everywhere you are and will touch or for some reason has caused a significantly higher concentration on your hands versus the environment?

Don't think so.

Bite your fingernails, or stick you fingers, hands on/in you mouth a lot? Stop or be aware of what you've been touching since the last cleaning.

That's not at all practical, though. Changing a habit such as biting fingernails is extremely difficult, and definitely not worth it to reduce the risk of getting a virus.

Bite your fingernails, or stick you fingers, hands on/in you mouth a lot? Stop or be aware of what you've been touching since the last cleaning.

That's not at all practical, though. Changing a habit such as biting fingernails is extremely difficult, and definitely not worth it to reduce the risk of getting a virus.

I was pretty surprised to see "definitely" here. If it significantly reduced your risk of getting a serious respiratory infection I'd expect it to be worth the effort.

Well, the "you" in the first bit was the universal "you" not Sil ver specifically. I think we're in agreement that thinking about the underlying risks and the benefits matter regarding the "wash your hands" -- but that is also a rather low cost prevention. But the point, which I think you were making and I was supporting, was that the policy should be understood in the contexts of what the underlying risk is and what risks the policy solution can actually address.

That type of question, is it worth it, seems to be more applicable to the get a mask, and particularly one of the type we always see in the media. It is my impression that the experience from SARS was that the direct contact was the largely transmission mechanism and hands are the primary vehicle that moved the virus to an entry point (mouth, eye).

I agree that habits can be very hard to break -- reinventing ourselves is hard. That said, being aware of our habits and what the implication are just makes some sense in the context of getting less wrong I would suggest. Again, it gets back to the context. Are you in a situation where paying attention to your habits makes a difference? If so make an effort at least on some habit hiatus or take the extra steps of washing/sanitizing your hands, in the case of biting fingernails.

Studying this with Anki is a waste of time in my opinion. Just execute the instructions three times and you're good to go. Physical skills are best learned physically.

Aside from that: Strong upvote!

Strange thing about the WHO guide: The nail area/tip of the thumb doesn't get much friction. Step 7 appears to address the space under the fingernails (which should be short anyway). But at least the lateral half of my thumb tip doesn't touch anything when I try it. Hm, maybe in step 6.

Studying this with Anki is a waste of time in my opinion. Just execute the instructions three times and you're good to go. Physical skills are best learned physically.

So this particular physical thing has one big advantage, in that you can go through the motions of it anywhere without much inconvenience or embarrassment. I think that makes at least a basic "practice this" card useful as a reminder. I'd predict that someone who had a periodic ping to check on/practice the habit would be more likely to keep it; do you disagree?

BTW, regardless of my skepticism on what is the perfect balance balance of time spent hand-washing, I will note that this post and discussion has done at least two things:

1) caused me to increase my hand-washing by about 75% (spending about 33% more time, about 33% more often).

2) spent more time in reading and thinking about it than just washing my hands a lot more would have taken in a year.

So, I'm either more knowledgeable and safer, OR wasting even more time than I otherwise would. Thanks?

Hey, at least (2) is good rationality practice. :P

My read of the various health authorities is that good, regular hand-washing is way ahead of gloves and masks in terms of keeping you and your loved ones safe.

From this 2014 meta-analysis:

The combination of hand hygiene with facemasks was found to have statistically significant efficacy against laboratory-confirmed influenza while hand hygiene alone did not.

I haven't looked into the paper carefully to see if it has any methodological issues etc., but this is consistent with what I've read elsewhere and common sense (i.e., masks filter out droplets and help prevent touching one's mouth and nose). The opportunity cost of wearing masks seems low enough that it's very likely a net positive.

masks […] help prevent touching one's mouth and nose

I agree in the case of someone who knows what they're doing. For many, however, a mask does the opposite. Yesterday I went out for two hours and saw someone re-pinching the wire above the nose, someone pushing the mask around their face, and someone taking the mask off and putting it in her pocket.

The latter seems innocuous, but think about it: Taking the mask off, she touched the outside, which had caught all the nasty viruses. Thereafter she ate lunch. Then, coming back from the cafeteria and after touching many shared surfaces, she probably put the mask back on, touching the inside in the process. Then the inside touches her face.

I came to the comment section expecting to see someone pointing out that not washing out your hands so much could improve your immune system by exposing you to more germs, pathogens, etc.

Well, since nobody did. I'm pointing it out. The argument seems sound to me. Is there something to be said against this perspective? Or something more in favor of it?

This argument has always seemed suspicious to me from a rationality perspective. Do you take other steps to deliberately expose yourself to pathogens (e.g. playing in the mud, or deliberately dropping your food on the floor before eating it, or licking unsanitary surfaces, or seeking out coughing/sneezing people to be close to)? If not, why not? Do you have some reason to believe the current level of exposure you get from not washing your hands is optimal (or at least close-to-optimal) from the perspective of improving your immune system through exposure?

The above paragraph probably sounds uncharitable. I can think of ways the "improve your immune system" argument might be true. There is an argument that early-life exposure to germs might strengthen the immune system and decrease allergies (the "hygiene hypothesis"). But it does seem to prove too much, especially given the vast and obvious gains in public health through hygiene and sanitation over the past 150 years. And it should seem especially suspicious when you're (a) going against a very strong expert consensus, in favour of (b) being lazy about something everyone kinda wishes they could just be lazy about.

It doesn't have to be optimal, the question is whether it is better. Is it better to wash all the time (as described in the post), like most people (let's say before eating and after using the bathroom), once-twice a day, or not at all (hands only washed during showers)? I'm not quite sure that "all the time" is better (it could be, but I'm not sure).

There is clearly a phenomenon of adapting to pathogens. I've heard it firsthand from at least two people who worked in less sanitary areas (South-American slums and Center-African countryside). There is no doubt to me that they were better off going through a bit of sickness in order to avoid the overheads of constant hand-washing.

I've also never heard heard about the gains in public hygiene due to hand washing in the general public (I mean that literally, I'm pointedly not saying they don't exist!). In a medical context, sure, the last thing we want is medical personnel spreading pathogens to vulnerable people.

Let me steelman the argument.

The first defense against outside germs is our microbiome. I do take steps like not using shampoo to avoid damaging my microbiome.

If the microbiome on your hand is already full of bacteria who live in happy coexistince with you it's harder for new pathogens to attack you then if you regularly kill the protective layer of the microbiome.

Beneficial effects of plant-associated microbes on indoor microbiomes and human health argues that if you put plants which aren't sterile into hospitals that has benefitial health effects because it results in a better ratio of harmless/harmful bacteria even if it raises the total amount of bacteria.

when you flush, you create a fine mist of very-much-not-clean toilet water that covers everything in the bathroom, including your hands.

This is why I always close the lid, if there is one, before flushing.

I don't know if you have it, or if I could find it, but there was a great time laps YouTube on that very thing. Lead me to try remembering to do the same (but is not as big of a deal as I live alone and rarely entertain at the house).

This one?

I hadn’t realised this was an issue but I’m definitely going to be remembering this in future!

Yes. I had forgotten about the tooth brush!

Good article, but pee-related note should probably be amended to add that women should clearly wash their hands after peeing, since we touch roughly the same number of of bathroom surfaces whether doing #1 or #2.

It seems like the recommendation is about preventing dirt on your hands to enter your body. If the hands of a woman are contaminated with a virus washing hands after going to the toilet instead of before poses the risk that the virus enters the body.

On the other hand unless you are currently ill, the pee will unlikely be a vector for viruses.

This part is a little crude but probably important. I've previously gotten into a couple of arguments about whether you should always wash your hands after peeing, given that (i) your junk probably isn't that dirty and (ii) there's lots of things in your house / around town that are more dirty that you don't wash your hands after touching.

There might actually be a stronger case to be made for washing your hands before peeing.

I don't want to come down against good hygiene practices, exactly, but my prior is that this is a completely unimportant change for most people to make. The waterline of sanitary practices in Western nations is high enough that increasing the frequency and thoroughness of the average person's handwashing seems likely to be subject to serious diminishing returns.

Consider that we're starting from a status quo where most people's hands are washed 3-5 times a day, even if lazily. Yeah it's not 100% effective, but I don't think it has to be in most circumstances.

Is there good epidemiological data that estimates how many disease transmissions have insufficient hand hygiene as an important/necessary vector? Because I would bet that outside of unusual cases like food service and medical workers, the number is low.

> Consider that we're starting from a status quo where most people's hands are washed 3-5 times a day, even if lazily.

Disagree, many people probably fall below this.

"it's not 100% effective, but I don't think it has to be in most circumstances."

Ineffective handwashing is basically useless other than removing visible dirt. The difference between doing a good job and doing a typical job is the difference between actually getting rid of the germs and preventing and infection or not.

"Is there good epidemiological data that estimates how many disease transmissions have insufficient hand hygiene as an important/necessary vector?"

Yes, and that's why epidemiologists and health economists keep recommending people washing their hands, putting up posters to that effect, etc.

"Because I would bet that outside of unusual cases like food service and medical workers, the number is low."

Yes, for food workers (who also do a bad job washing, and can't/don 't take time off when sick,) the impact is far worse.

Source: Forthcoming paper I wrote with Dave Denkenberger.

There's enough variance that relative recommendations ("more often", "more completely", "more time spent") are difficult to take seriously.

I wash my hands maybe 2-3 times per day and apply Purell (the brand provided at work) another 1-2. I don't spend over 10 seconds, though I do try to get all surfaces. Will the marginal improvement of adding one instance or 5 seconds of additional scrubbing noticeably reduce my risk? I can't find any study that has this level of granularity.

Is there good epidemiological data that estimates how many disease transmissions have insufficient hand hygiene as an important/necessary vector?

As opposed to what? Direct airborne transmission via breathing in droplets?

My model of the spread of colds and flu and so forth is that it is primarily down to bad hand hygiene. I'd predict (with pretty low confidence) that more people get infected through getting virus on their hands and then onto their face / into their mouth than by breathing in virus directly. I'll look into this more when I get the chance, though, since lots of people are asking about this.

Droplets would be number one on my list of transmission vectors for people other than the hand hygiene intensive cases I mentioned, yes.

Droplets don't usually float around very long. It seems most transmission would still require something going into a person's mouth. A small portion of these droplets hang around in the air and can be breathed in, but poor hygiene seems like a far bigger issue given how often people touch their face, mouth, and food.

Also worth noting that, depending on the virus, particles outside a host can often survive for hours or sometimes days. To get infected by direct inhalation you'd need to be fairly close to a sick person when they were shedding virus into the air – i.e. to be very close to them in both space and time. To get infected through surface contamination the time requirement is much less stringent: you only need to be where an infected person was fairly recently. If you don't have good hand/face/mouth hygiene, they can infect you without your ever seeing them or knowing they were there.

I 've seen somethings concerning how dirty cellphones are - and how they can worsen interpersonal disease transmission. I wonder if there's any advice on how to keep it clean (and how useful would it be).

Yeah, this is something I worry about as well. It's probably a good idea to clean your phone with hand sanitiser regularly, but unless you're doing it multiple times per day (which nobody is) it's still going to be a big problem. AFAICT most people never clean their phones at all.

If you are the only person touching your smart phone and not give it to other people that should reduce a lot of the potential of them as a vector. If you in addition don't press it against your face, it's not clear to me why it would make sense to worry about it.

If you grab your mobile with your dirty hands, then wash them, and then use your device again, you just recontaminated them; and if you never clean its surface (how do we do it effectively?), it'll accumulate pathogens. This seems to be a serious problem in hospitals.

(I'm not sure if I follow your reasoning; it apparently implies that, if you never shake hands with someone else, you never have to worry about washing them. Of course, it does reduce the potential for transmission.)

You aren't just touching other peoples hand directly. You are usually touching doornobs, light switches and other objects that other people are also touching.

There's a nice way to combine the WHO guide with the trick of singing "Happy birthday" twice to time the ~20 seconds that handwashing is supposed to take. You do steps 1 and 2, then sing "Happy birthday to you" while doing step 3, then sing "Happy birthday to you" while doing step 3 with reversed hands, then sing "Happy birthday to meeee" while doing step 4, etc.