I was talking to my sister yesterday, and we somehow got onto the subject of washing hands before eating or handling food. She is of the opinion that hand sanitizers do more harm than good. They may not remove such pathogens as e-coli, but they might remove beneficial germs that we need in our diets.
Huh?
I pressed her for details, but she can’t seem to remember where she heard it. She reads a lot of medical journals, but she also hangs around with a a lot of people to whom facts mean very little.
I’m not sure that our hands have different bacteria from the rest of the world around us but us humans (and many other animals) rely on huge amounts of bacteria to allow our bodies to do their job properly - the majority of which are in the gut. There is no doubt in my mind that companies play on a largely unfounded fear of bacteria encouraging the public to over-sanitise surfaces that just don’t need it. And in probablity, it does slightly more harm than good.
The parent who surgically cleans their child’s environment is probably not doing them any favours.
Someione from the medical profession should be along shortly to confirm, refute or eleborate on my reply…
I’m well aware of the amount of bacteria we need in our guts to digest food. It just never occurred to me that they might get there because of our hands. :eek:
I read recently (on these boards, maybe?) that newborns don’t have that internal bacteria. How does it eventually get into us?
One way in which our natural skin flora benefit us is that they consume resources that would otherwise be available to allow pathogenic organisms to get an easier foothold.
I’d like to see some cites for the dangers of over-sanitized environments. One of my friends has two eight-month old infants, and she raises them in an environment that approaches a Silicon Valley clean room, going so far as to keep them off the floor at all times, for fear they’ll contact bacteria that someone brought into the house on their shoes. I’ve told her I’m concerned they’ll have problems developing their immune system, but she’s extremely protective, fearing that the kids will get sick if they come into contact with any germs.
Seems to me like she’s conflating several unrelated ideas.
First, there’s the idea that probiotics are important in a healthy diet. Basically we have a vast and amazingly diverse set of bacteria growing in our gut, and they provide many health benefits to us. Some provide nutrients, and generally a healthy gut flora will keep our digestive system running smoothly and prevent nastier bacteria from colonizing. Witness, for example, the extreme … intestinal discomfort … that is a common side effect of treatment with powerful antibiotics. In our diet, we can use foods like yogurt and other dairy products with live cultures of certain bacteria as probiotics. IMO, the benefits have been exaggerated by advertisers, but there’s good medical evidence.
However, the bacteria that live on our hands are NOT considered useful probiotics. One of the most common skin bacteria, staphylococcus, is usually harmless but it’s very opportunistic. Certain strains in particular can cause nasty infections given the opportunity (such as a cut or abrasion). The more benign strains will happily colonize your skin and prevent large-scale establishment of more aggressive strains. But even the benign species can cause unpleasant cases of food poisoning. It’s not that they’ll easily infect your digestive system (staph is effectively killed by the acidity in your stomach), but rather that your immune system detects a common invader and triggers the “emergency purge” response".
So there is some valid concern about killing off all of your skin bacteria, similar to concerns about killing off the gut flora. But this is mostly a problem for the elderly and immunocompromised. Besides, even a thorough scrubbing with soap or alcohol-based hand sanitizer won’t sterilize your hands – you’ll still be left with enough bacteria to re-colonize.
What hand sanitizer or hand washing in general WILL do is prevent the spread of many diseases. Viruses and bacteria are effectively killed by either (though antibacterial soap is no better than regular soap). So if you don’t wash your hands before cooking, you’re much more likely to spread a cold or flu virus, and you’ll inoculate the food with a larger amount of bacteria that will cause food poisoning (if you give them a chance to grow). And you’re also increasing the likelihood that you’ll spread a rare but nasty disease, such as that O157 strain of e. coli* that likes to colonize meat from poorly managed meat packing plants.
*though I want to emphasize that ordinary, garden-variety e. coli is nothing to fear. It’s living in your gut right now, and on your skin, and every surface you’ve touched. But it won’t make you sick because essentially you’re already as infected as you can be, and it’s one of the helpful bacteria in your gut. The real problem is that there are a few nasty pathogenic strains out there that can be life threatening.
There’s no conclusive evidence on this topic, though personally it’s an idea give a lot of credence. The term to look for is the hygiene hypothesis. Basically the idea is that a too-clean environment won’t challenge the immune system properly. A child in that environment won’t gain immunity to various common diseases, and might be more susceptible to them when they are older and their immune system isn’t quite as flexible. Chicken pox is a fairly concrete example of this idea, but we don’t know how well that extends to more common and less serious diseases. Also, given a lack of challenges from actual pathogens, it’s thought that the immune system will start attacking more benign “invaders” like pollen or pet hair, giving us allergies. Or even our own body, given rise to autoimmune disease. Wiki has a pretty good summary of the hygiene hypothesis.
The evidence from this primarily comes from large-scale epidemiological studies. Basically, kids that grow up on farms, particularly those that take care of a variety of livestock, tend to have a lower incidence of allergies and asthma compared to kids growing up in urban (presumably cleaner) environments. Also, kids that have a large number of siblings around (presumably exposed to more pathogens) also tend to have fewer allergies. In lab animals, mice that are raised in a completely sterile environment (no easy task!) are less healthy than animals that aren’t. But there’s no clear evidence for a causal relationship in humans – just lots of very intriguing correlations.
To expound upon the hygiene hypothesis, there is some evidence that asthma and allergies occur because the immune system is not “primed” enough when the child is young. One study showed that a non-specific immune stimulator in BCG vaccine seemed to be protective for asthma.
And while I can’t find the link, I did see a paper that reported that both parasitic worms and TB infection in early childhood was protective against allergies and asthma.
We need normal flora to compete with pathogens and we need exposure to moderate pathogens to develop healthy immune systems against bad pathogens.
The naive immune systems of the Original Peoples of the Americas is thought to have been a contributor to their deaths from diseases to which the invading Europeans were relatively immune…
Although I think the theory is completely plausible and reasonable, the problem with the above is that the rats you capture from the sewers might just be fitter because the ones that weren’t fitter died early in their lives and so were not there to be captured.
I await the second part of the research with bated breath:
“Parker said he hopes to build a 50-foot artificial sewer for his next step, so that he could introduce the clean lab rats to an artificial dirty environment and see how and when the immunity was activated.”
That would be a great grant proposal:
“We will need funds to build a 50-foot sewer and volunteers to create the sewage…”