Showers: A dirty business?

In the movie Sex and the City germaphobic Charlotte forgets herself and sings in the shower while in Mexico -- accidentally swallowing some bad water -- which to the amusement of her friends, causes her to have a little, uh, 'accident'.

Now scientists say you don't need to be in an exotic location to experience unhealthy side effects of a shower. Recent tests conducted in nine US cities showed that dirty showerheads harbour bacteria called Mycobacterium avium (M.avium), which can cause lung disease.

In the analysis, the levels of M.avium were 100 times higher than those found in typical household water supplies.

"If you are getting a face full of water when you first turn your shower on, that means you are probably getting a particularly high load of Mycobacterium avium, which may not be too healthy," lead researcher Professor Norman Pace from the University of Colorado at Boulder said in a statement.

For the study, published in the National Academy of Science, researchers tested 50 showerheads from nine cities across the country, including New York City, Chicago and Denver. They found that 30 per cent of the devices posed a potential risk.

Showers: a dirty business?

M.avium forms a biofilm that clings to the inside of the showerhead -- which means that hot, relaxing shower can distribute bacteria-filled droplets that are easily inhaled into the deepest parts of the lungs. In the past, showers have also been found to spread other infectious diseases, including a type of pneumonia called Legionnaires' disease and chest infections with a bacterium called Pseudomonas aeruginosa.

These findings may explain why there have been more cases of these lung infections in recent years, linked with people who tend to take more showers and fewer baths, the study authors say.

So is it dangerous to take showers? "Probably not, if your immune system is not compromised in some way," said Pace. "But it's like anything else -- there is a risk associated with it."

Apparently infection is rarely a problem for most healthy people. At higher risk are those with weakened immune systems, like older people, pregnant women or those who are fighting off other diseases.

Symptoms of a lung infection caused by M.avium include fatigue, a persistent, dry cough, shortness of breath and weakness.

What can you do?

So can you clean your showerhead? Professor Pace and his team tried that, but ironically, the effort seems to have made it worse. Cleaning a showerhead with a bleach/chlorine treatment led to a three-fold increase in the bacteria several months later.

He does, however offer this tip: Go with a metal showerhead, since the plastic ones appear to "load up" with bacteria-rich biofilms.

It's also a good idea to let the shower run for a few seconds before stepping in. And, oh, close your eyes -- and forget singing in the shower.

Sources: University of Colorado news release; National Academy of Sciences; BBC.

Photo ©iStockphoto.com/ Natthawat Wongrat

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