Bacterial showers?

Along the lines bs king’s comment about teaching high schoolers how to spot bad science reporting, how about a step by step walkthrough of a science claim?

”I have not taken a shower in over 12 years,” says Dave Whitlock, a chemical engineer and MIT grad who says he doesn’t miss bathing at all. “No one did clinical trials on people taking showers every day. So what’s the basis for assuming that that is a healthy practice.” So . . .

In fact, what Whitlock does believe is healthy is restoring good bacteria to our skin that our ancestors enjoyed long ago and that has slowly been stripped away by excessive cleaning. To prove his theory, he helped found AOBiome, a company based in Cambridge, MA.

Maybe your BS meter pegged already, but just for the sake of the exercise let's see what simple searching does for us.

We are fortunate to have search engines to help us.(*) One of the first things that pops up for "skin bacteria" is Wikipedia’s “skin flora” And one of the first sentences is “Many of them are bacteria of which there are around 1000 species upon human skin from 19 phyla.” You can also read about fungi, and note that there are skin diseases. That 1000 is an interesting number—it isn’t gigantic, but it isn’t tiny either. We’ll get back to that. Notice that the term “hygiene” turns up. And “damaged skin.”

First we pick one of the random organisms mentioned (this one inhabits frogs): Batrachochytrium_dendrobatidis. The article contains a lot of $40 words, a few of which you can piece out, but a couple of things strike your attention. It was first discovered in 1998, and only recently was found to be a number of different varieties. And the references listed at the bottom show a lot of different authors—I quit counting at 21 and guess there were more like 50-60. All for one variety or set of varieties of organism. The first article says there were 1000 bacteria types, let alone the fungi.

How many people do you need to study all 1000? Or better, how many man-years of study? 50,000?

Second we take warning from the fact that skin diseases exist, and start our search again for skin diseases. One of the early ones that pop up on the list is candidiasis (acne we won’t worry about). Funny how the term “hygiene” keeps showing up. Warm moist undisturbed areas help the fungi grow. And also notice that among the contributing causes is “taking antibiotics that kill normal flora.”

That last sentence sets up another warning flag. The bacteria and fungi interact. So we don’t just have to study each of the bacteria in isolation, we have to study them in combination. So we have not 1000 bacteria, but 1000*999 pairs to study—not to mention triples. (That’s about 50 million man-years to study the pairs, for those counting.)

I’m certain there aren’t a million researchers in the field, so I conclude that we don’t completely understand all the interactions of skin flora with our bodies or with each other.

But do we understand it “well enough?” (We don’t thoroughly understand metals and concrete, but we can build a bridge that can last a century of heavy use.)

What research is Dave Whitlock building his model on? Unfortunately looking him up brings up a more famous fly fisherman and race car driver. The Daily Mail's report has a little more detail on the man than the CBS story, including these bits

Although he doesn't shower, Whitlock does take an occasional sponge bath to clean the grime off of his skin.

And

The scientist got the idea about 'good bacteria' when a woman he was dating asked him why her horse liked to roll on the ground and the dirt during the summertime, the New York Times reported.

Whitlock said: 'The only way that horses could evolve this behavior was if they had substantial evolutionary benefits from it.'

According to the company: 'Modern hygiene has selectively depleted the natural balance of the skin microbiome particularly affecting AOB.

The company web site includes this “We are developing a new class of transformational products based on the use of beneficial ammonia-oxidizing bacteria (AOB). AOB are naturally occurring bacteria that metabolize the ammonia found in sweat, creating both nitrite and nitric oxide, two critical building blocks of good health.”

What I don’t find (maybe your search would be more productive) is any links to any research showing that having nitrites form in your sweat is good for the rest of your body. I’d think that sweat is mostly a one-way phenomenon, though I’ve heard many times of things being absorbed through the skin. Maybe you’d stink less—ammonia is kind of acrid, and if some bacteria destroy it that might be good.

He’s a chemical engineer and not a biologist, but a gifted amateur can do a lot, so I won’t count that for or against his claims.

Let’s score the findings.

On the plus side, he claims that the skin flora can be disrupted by washing. This we know to be true about antibiotics, and soap also has an antibiotic aspect. In addition, though he isn’t quoted as mentioning it, damage to the skin can cause opportunistic infections by otherwise benign bacteria (from that first Wikipedia article), and aggressive scrubbing can damage the skin. (Why do people exfoliate anyway?)

On the minus side, we know that we don’t fully understand bacterial/fungal interactions on our skin. And he doesn’t cite any research explaining how any of this works.

On the minus side, he doesn’t have any of our ancestors handy to take skin bacteria cultures from. The next best thing would be to find some people who don’t use soap back in the jungles, and take some samples from them. And maybe see if they are more or less susceptible to skin diseases. (In the tropics there turn out to be a lot of endemic diseases, so maybe that’s not a fair comparison.) But once again, not a peep.

Minus again: no mention of whether this prevents athlete's foot. Washing regularly does help.

On the “Hey Wait A Minute” side, I can’t find out whether he recommends washing your hands after using the toilet. I hope he does, and that the reporters simply never had the wits to ask, but that’s an obvious case where washing matters.

Summing up: I don’t know if he is right, but he hasn’t given me any reason to believe that either

1. The rebalancing of flora that results from washing is in any way bad for us
2. His bacterial spray rebalances in a beneficial way

Not proven, and if he wants me to buy his product or cheer him on, he needs to show some evidence. Let’s see some of those clinical trials he was talking about. Blinded, with controls.

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(*) Wikipedia has some good math articles, and in science it's generally OK, but don't trust it for anything controversial.