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Is hand-washing after urination and defecation merely a product of social norms, or is there a health-related reason that we wash our hands after going to the bathroom? Or is there some other reason altogether?

Oddthinking
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Cory Klein
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    Offered without evidence: Just one of the reasons to wash your hands after using the bathroom, is that proximity to a hand-basin offers a good opportunity to wash your hands several times a day, which is good hygiene practice in itself. – Oddthinking Jul 17 '12 at 02:23
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    In one Southpark episode it is said that it would make more sense to wash your hands before you go to the toilet, because your hands are probably much dirtier from all the stuff you touched than they can get from touching yourself. – Baarn Jul 17 '12 at 12:46
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    I suspect that this is going to be somewhat dependent upon what you are doing in the bathroom and how you go about doing it. I've heard that for males that hand-washing is effectively unnecessary, assuming that they don't touch any of the bathroom surfaces due to the fact that urine is sterile. – rjzii Jul 17 '12 at 12:51
  • Forgive me if I misunderstand but, are you asserting that wiping your own feacal matter across your face carries no inherent risk to health? – Jodrell Jul 17 '12 at 15:40
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    @Jodrell If the amount of fecal matter is miniscule to where it is difficult to see with the unaided eye, which is often the case, I think this is a valid question. Am I going to catch a disease from myself? I don't think so, because then I would already have it. – Cory Klein Jul 17 '12 at 15:44
  • I honestly can't say for sure but I do know I'd prefer to be in the control group. Maybe the matter could act as a substrate for bacterial growth. – Jodrell Jul 17 '12 at 15:53
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    @Cory From yourself – no. But potentially from other people who you touch – either indirectly or via touching the same objects as them, and who failed to wash their hands after getting into contact with pathogens from the urinary or intestinal tract. – Konrad Rudolph Jul 17 '12 at 20:40
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    Just based on this example: http://en.wikipedia.org/wiki/Cysticercosis#Life_cycle not washing your hands can make you sicker/cause more problems. (if you have already been infected through food) – Stefan Jul 17 '12 at 21:39
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    @RobZ: I don't know about you, but I don't touch the urine itself when in the washroom, so it's a moot point whether it's sterile. I do, however, end up touching parts of my own body which are in close proximity to, and share an undergarment with, the place where the poop comes out. So I think it's safe to assume some minuscule fecal transfer must happen. – Larry Gritz Jul 19 '12 at 18:32
  • In the US there are signs in restaurant bathrooms that say "Employees Must Wash Hands Before Returning To Work." When I was unemployed I thought, 'well, that is one less thing to worry about!' I saw once where someone wrote on the sign "Everyone is an Employee" which is not quite true. So, watch out for retired and unemployed people in the US! –  Mar 09 '16 at 02:10

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Without washing your hands after going to the toilet, you are running the risk of E. coli enteritis. E-Coli can lead to severe illness or even death. Keep in mind, every time you flush the toilet that a plume of water droplets can spread by up to a couple of metres, coating tooth brushes and such in contaminant. This is also backed up here.

In response to OddThinking: If you were to only touch yourself I would reason that the risk remains. As noted above, everything within a few metres of the loo is likely to be swimming in bacteria, especially if the lid was not closed when it was last flushed. So just entering the bathroom is problematic.

Furthermore, people fart about a litre of gas a day. Since farts contain bacteria, you can pretty much assume your clothes and body are also contaminated. This was posted on Dr Karl's site. The Naked Scientist tested the effect of clothing on bacterial content of farts and found the clothes (jeans + undies) seem to absorb the bacteria.

Taking this further: can you make yourself sick with your own facel material? Given that 20% of food poisoning occurs at home, I would think so.

dave
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    Your references seem to (quite rightly) recommend washing your hands to avoid contaminating others. However, this doesn't address the question - can you make yourself sick? – Oddthinking Jul 17 '12 at 02:27
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    @Oddthinking - updated. I'm still not 100% convinced though. Certainly my cat seems to suffer no ill-effects from self cleaning, and (please) let's not talk about 1 cup 2 girls. – dave Jul 17 '12 at 02:52
  • I think this answer might be on the right track, but may need to address the biological differences between men and women as it relates to urination. As I noted in a comment on the question itself, there tends to be a belief among men that hand-washing is largely unnecessary following use of a urinal as long as they don't touch anything in the bathroom. – rjzii Jul 17 '12 at 12:53
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    Isn't the fart-bacteria you mention "good" bacteria in the digestive tract? Is it actually harmful? And even if it is harmful bacteria, then you're not going to make the situation worse by making your clothing or epidermis "contaminated" when it is already existing inside you in abundance. Am I wrong? – Cory Klein Jul 17 '12 at 15:45
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    Also, you link "20% of food poisoning" to the wikipedia article for flatulence, which provides no reference to food poisoning, and specifically mentions that flatulence is not poisonous. – Cory Klein Jul 17 '12 at 15:53
  • @CoryKlein - Good bacteria in the digestive tract(colon) becomes bad bacteria in the lungs, mucus membranes, or on your skin, not to mention other organs it should never get access to. – Chad Jul 17 '12 at 16:13
  • @CoryKlein - 20% reference fixed. – dave Jul 17 '12 at 20:29
  • @RobZ - Given the proximity of the penis to the anus, I'd say its fair to assume that the penis is likely to be covered in the bacteria emitted from flatulence. – dave Jul 17 '12 at 20:34
  • @Oddthinking Where in the question do you see that it asks whether you make yourself sick? – Konrad Rudolph Jul 17 '12 at 20:43
  • @dave - I still haven't seen anything to back up the "flatulence contains bacteria" claim, but I did find an article on [The Straight Dope](http://www.straightdope.com/columns/read/1043/why-are-men-supposed-to-wash-their-hands-after-urination) that covers hand-washing for men and also effectively provides an answer for women well. Briefly, coliform bacteria are present from mid-thigh to belly button regardless on cleanliness due to their presence in the pores so hand-washing is needed to get rid of ones that are picked up though surface contact with any part of that region. – rjzii Jul 17 '12 at 21:58
  • An episode of mythbusters disproves your claim that everything around the toilet is contaminated. They tested a number of locations around a shop and surprisingly the place where the least bacteria was located was actually next to the toilet. Myth busted! – Dunk Jul 17 '12 at 22:54
  • @Rob Z: Dr Karl posted an experiment on farts [here](http://www.abc.net.au/science/k2/homework/s312551.htm) showing bacterial content. The [Naked Scientist](http://www.thenakedscientists.com/HTML/content/interviews/interview/917/) also did tests on bacteria and farts with pants on and pants off. – dave Jul 18 '12 at 01:59
  • @Dunk: It's not actually my claim about toilet contamination. [This](http://www.dailymail.co.uk/health/article-2081680/How-leaving-toilet-lid-flushing-aid-spread-winter-vomiting-bug.html) has a bit of research behind it. As you noted, the Myth Busters concluded the toilet had the least bacteria - that's not the same as none. – dave Jul 18 '12 at 02:07
  • @Konrad: Um, the 2nd sentence. I am trying to see a second interpretation, but can't. This probably makes the claim non-notable. (Who is making it?) – Oddthinking Jul 18 '12 at 02:25
  • @Oddthinking The answer to that sentence is: yes, it’s still medically indicated because you make *others* sick, even if not yourself. – So I don’t think it’s only talking about making yourself sick. Actually, the second sentence doesn’t mention making yourself sick at all. – Konrad Rudolph Jul 18 '12 at 07:05
  • @Konrad: If the question is "Should I wash my hands?", let's simplify the verbiage. If the question is "Can I get sick if I don't come into contact with anyone else, and I don't wash my hands?" lets close the question as non-notable. – Oddthinking Jul 18 '12 at 07:33
  • @Oddthinking I’m very much in favour. Can you come up with a better formulation? I’m unfortunately a bit short on time since my qualifying seminar for the thesis proposal is tomorrow. – Konrad Rudolph Jul 18 '12 at 08:39
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    @KonradRudolph and Oddthinking - I think maybe we are reading a bit too deep into the question here. What inspired this question for me was that most of the physical objects I touch in the bathroom are used specifically for washing and drying my hands. After pooping I touch the toilet paper, but then it goes in the toilet. So to me it seems that the process of washing hands introduces more touch surfaces, and that additional risk may be obviated by just not washing at all. So everyone says we should wash our hands when using the restroom, but is that really true? Does that really help us? – Cory Klein Jul 18 '12 at 15:00
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    @Cory: Signs saying "Wash your hands to prevent the spread of disease" are notable. Signs saying "Wash you hands to protect *yourself* from the surfaces you touched since you entered the bathroom." are not (it appears to be just your speculation.) Answering the first claim will be much easier than answering the off-topic, speculative claim that no-one has made. – Oddthinking Jul 19 '12 at 11:21
  • @Oddthinking I had understood that placing these signs in the bathroom implicitly added that specification to the claim. Besides, I didn't learn just from signs to wash my hands when I go to the bathroom, but it is a widespread social reinforcement that has been communicated verbally as well, often including the "bathrooms have germs that you need to wash off 'cause you touched them" specification. Does that not qualify it as being notable? – Cory Klein Jul 19 '12 at 17:32
  • @Oddthinking, sorry, I know I'm new to skeptics, and I tend to be an argumentative personality in general, but I'm not intentionally trying to be difficult. Maybe we just need to discuss this privately so I can understand what's going on better. – Cory Klein Jul 19 '12 at 17:37
  • People, please move this to the [chat] if necessary. I will clean this thread later on. – Sklivvz Jul 19 '12 at 19:02
  • Well... But how to wash properly? And if not washed properly, is it still better than not washing? Finally, isn't it more important, then, to wash it regularly rather than "after the bathroom"? I mean, dangerous bacterias are everywhere and we never really know where. A clean bathroom might be much less dangerous than a dirty room. – cregox Sep 15 '15 at 20:02