When Did You Last Clean Your Showerhead?

It could be time to get to work.

Apparently it was the Greeks who started it all. Part of an ancient Greek’s daily bathing routine consisted of emptying a jug of water over their head or, if they were wealthy, having a servant do it for them.

These days, of course, you don’t need a jug. It’s common to take a shower, and according to a 2016 survey by the market research company Euromonitor, around 70% of Americans start with one every single morning.

Surprisingly however, we aren’t quite as dedicated to our showers in the US as those in Colombia and Brazil, where just about 100% of adults make their way into the spray every morning.

Many hygiene experts say this may actually be overdoing it, though, as there’s some suggestion that daily showers rob our skin of important oils.

But there’s another reason to think twice about showering, which is that your showerhead might just be harboring bacteria, then blasting it onto your body, and possibly even into your lungs. This is one of the reasons why a study led by North Carolina State University is asking 500 people in the US and Europe to send them samples of the gunk they’ve collected from inside their showerhead.

Nicola Twilley, writing recently in The New Yorker, described what she found when she removed the faceplate of her own showerhead in order to participate in the study. It was “a slimy, slightly clotted dark film, covering the stainless steel interior.”

Nice.

The North Carolina study is being run out of The Rob Dunn Lab, Rob Dunn being a professor of applied ecology at North Carolina State.

His website explains that microbes can colonize the insides of showerheads, raining down on you as you shower.

But showers also produce an aerosol effect – resulting in minute particles becoming suspended in the air, from where they can readily enter your lungs.

However, the site goes on to explain, there’s an enormous difference between the amount of gunk (biofilm is actually the scientific term) found from one showerhead to another. Appearances can be deceptive.

While some generously ooze with biofilm inside, others have none – and this can even apply, in the lab’s own words, to “old, gunky, terrible-looking ones of the sort you might find in the hostel of your nightmares.”

The researchers believe that some of this difference may be down to the municipal water shooting through the showerhead, but it’s thought that climate can also play a part.

Showerheads, of course, are wet at certain times, then generally dry out completely before their next use, and this wet/dry regimen can favor the growth of unusual sorts of microbes.

The lab says it is even possible that some showerheads may contain bacteria-eating amoeba which keep the plumbing clean.

One of the team’s researchers, Jennifer Honda, a microbiologist from University of Coronado Anschutz Medical Campus, will be looking for non-tuberculous mycobacteria (NTM), a pathogen that can cause lung disease in individuals with compromised immune systems.

She will be testing the hypothesis that NTM will be more likely in tropical climates than in temperate ones.

In tropical conditions, she explains, the showerhead has less of a chance to dry out.

If the genus Mycobacterium makes you think vaguely of mushrooms, that’s not an entirely misplaced idea.

“Myco” is Greek for “fungus,” and the genus was given its name because Mycobacteria tend to grow in a fuzzy, mold-like fashion.

Another study, involving a species from this genus – again involving showerheads – was carried out at the University of Colorado in 2009 by Dr. Norman Pace, a professor of molecular, cellular, and developmental biology.

In this case, he was interested in Mycobacterium avium, one of a collection of microorganisms that can cause pulmonary (lung) disease.

Dr. Pace explained that as well as those microbes that accumulate in the showerhead, others are continuously added via the water supply.

His research showed, however, that whereas Mycobacterium avium may be present at levels of 0.1-1% in the water coming into the shower, it may make up to 70-80% of the biofilm in the showerhead itself.

What about chlorine in the water supply? Shouldn’t this kill bacteria?

Well, some, but not all, since Mycobacterium avium is actually fairly resistant to chlorine.

In a 2009 interview, Dr. Pace suggested that breathing in this particular bacteria could cause a “low-grade cough that persists for months,” making you feel “lousy, weak,” and leading to, perhaps, “breathing difficulties.”

Dr. Pace explained that Mycobacterium avium pulmonary disease is “very undiagnosed” and is a condition that isn’t nationally reportable by the CDC.

If you are concerned about the possibility of Mycobacterium avium, Dr. Pace suggested you might think about taking a bath rather than a shower, significantly reducing the possibility of aerosolization.

Of course, as in all matters bacterial, there are both bad guys and good.

In fact, Rob Dunn’s research will also explore the possibility that shower-delivered bacteria might actually benefit us by introducing microbes that strengthen the human immune system.

The study’s website points out that showerheads are one of the few places from which we can get exposed to lots of weird microorganisms, which can be a good thing.

Rob Dunn seems to have built a career out of exploring the wilder side of micro-life.

His past work has involved: a study of bellybutton microbial diversity, looking at the population dynamics of facial mites, and a multi-year survey of household dust.

Alongside his showerhead research, he has also recently launched a study of sourdough bread, prompting him to conflate the two into the “Showerdough Project.”

Rob Dunn suggests that one possible reason for the belief that females make better-tasting bread than men is that their hands could be colonized with lactobacilli (which are more supportive of fermentation) originating from their own vaginas.

This fascinating reflection led one online commenter to claim, “I’d eat the vagina yeast bread, but I wouldn’t want to lick a showerhead.”

Quite.


Further reading

Bacteria May Lurk on Your Showerhead

No one escapes the microbiome

Opportunistic pathogens enriched in showerhead biofilms

Personal Appearances: Global Consumer Survey Results on Apparel, Beauty and Grooming

Rob Dunn

Showerhead Microbiome Project

What’s Lurking in Your Showerhead

What’s Hiding In Your Showerhead

Which Country Takes the Most Showers?

4 thoughts on “When Did You Last Clean Your Showerhead?

    1. Gae Seal

      How do you clean your shower head? Do you remove it entirely to soak it in vinegar or do you have a way to suspend the vinegar solution around the existing shower head?

  1. Pingback: Microbiome Awareness Month – Showering in Microbes! – uBiome Blog

  2. Kathy

    My son already had tuberculosis, took a year to cure that and this left him with one lung that wasn’t in the greatest shape itself, then he gets MAC, mycobacterium avium complex. We aren’t sure how, but this could be why, an old shower head, almost killed him as he was already compromised.

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