Another look at soap and science


Earlier today, guest blogger Sean Bonner posted a study that he said supports his decision to live a soap-free lifestyle.

Now, I don't really care too much about the soap/no soap debate one way or the other. Although I have not personally met him, Xeni assures me that Mr. Bonner really is pleasant to be around, without any funky odors to him. And, regardless of his success, I'm not likely to give up things like shampoo and apricot scrub anytime soon, due to my own personal experiences managing my hair and skin.

But, I thought it would be interesting to do a Google Scholar search, and try to get an idea of what the scientific literature, as a whole, says about the value of soap. Or lack thereof. Before you read on, please note that I'm not sure how applicable this information will be to the specific soap/no-soap partisan divide here on BoingBoing. Most of the research I found was either studying handwashing practices among health care workers, or sanitary precautions in parts of the world that have ongoing problems with some nasty communicable diseases that aren't really a big deal in the United States and Europe.

That said, here's what I found:

•So, first off, the study that Sean Bonner cites isn't necessarily a great argument for the superiority of water-alone washing. Only about 40% of healthcare workers comply with handwashing guidelines (yipes, right?), so people are constantly looking for ways to reduce disease carrying. The idea behind this study is that, even if the soap-and-water method works best, it doesn't help much if people don't do it. If they will use a squirty gel thing, even if it it kills fewer germs than the soap, maybe you're still better off in the long run. The goal wasn't to prove what cleaning option was best, but to see how well the non-washing-based options did, with the idea of choosing one to use as a realistic alternative to handwashing. You'd want to set up a different sort of study to test the question of whether people are better off without soap.

This study ran two sets of trials using a bacteria in one and a virus in another, with 14 different cleaning options, including the two controls—water alone, and soap and water. With the virus, after 10 exposures, water alone was killing the most bugs, followed closely (closely enough that you can't really say water alone was absolutely better) by plain soap and water. But with the bacteria, the situation was different. After 10 exposures, water and soap-and-water were again running neck and neck, but they were both at the bottom of the pack. Soap with 2% chlorhexidine gluconate won the day.

Basically, this one study doesn't tell us much about soap vs. no soap.

• I didn't find any studies that directly compared whether washing with soap or washing without soap killed more germs. Doesn't mean they aren't out there. This was kind of a cursory scan. But it's safe to say that this question isn't of the utmost importance to most public health researchers.

• One of the reasons healthcare workers don't wash their hands as often as they should is because of soap-induced irritation of the skin. There are lots of studies addressing this problem. But, again, healthcare workers are outliers. If you aren't a healthcare worker, and you're washing your hands as often as they are—often enough to get serious skin irritation—you might want to try less frequent washing before shifting toward giving up soap entirely.

• A systematic review of the literature on handwashing and diarrhoeal disease (meaning that the researchers reviewed and compiled data from every study done in a specific way, on this specific topic) found that "washing hands with soap can reduce the risk of diarrhoeal diseases by 42-47% and interventions to promote handwashing might save a million lives." Again, bear in mind, this is talking about developing countries, and it doesn't tell you whether washing without soap would have done better. But it does seem like there is some value to soap.

• I saw a study called "Soap May Seriously Damage Your Health", and thought I'd hit a jackpot. Turns out, it's actually about soap operas. Apparently, there's a correlation between the popularity of a specific suicide method, and whether a TV character has used that method to kill themselves recently.

• Not washing your hands after using the bathroom, and not washing dishes and utensils thoroughly, has been associated with an increased risk of diarrhea among American wilderness hikers. One study specifically called out the use of soap as a protective behavior. Apparently, previous research has shown that you need to use some kind of rubbing agent (soap, ash, or dirt, in the case of campers and backpackers) if you want to actually get fecal matter and the contaminants it carries off of your skin. Which, you know, you do.

Bottom line: I can't conclusively say whether soap is better than no soap. And it seems like the no-soap option is significantly better than no washing at all. But there is, at least, some research out there suggesting that soap is better—in certain situations—at preventing diarrhea.