First it was Alfred Hitchcock's film, Pscyho, that had us all terrified of the shower. This time the University of Colorado researchers are the purveyors of fear.

Researchers from the University of Colorado at Boulder found the levels of bacteria in shower heads were 100 times higher than those found in typical household water.

In researching 50 shower heads, 30% were found to have dangerously high levels of bacteria--and of most concern 20% were found to have dangerous levels of Mycobacterium avium, which is linked to pulmonary disease and lung infections, and can cause symptoms such as a persistent dry cough, breathlessness and fatigue. Mycobacterium avium most often infects people with compromised immune system but it can occasionally infect healthy people.

"Researcher Norman Pace said research at the National Jewish Hospital in Denver found that increases in pulmonary infections in the United States in recent decades from so-called "non-tuberculosis" mycobacteria species like Mycobacterium avium may be linked to people taking more showers and fewer baths." --Reuters

The shower head converts water droplets into smaller-sized particles which are suspended in the air. Due to their small size, they are easily inhaled into the deepest part of the lungs and absorbed. The heat and steam from the shower, once thought to be of health benefit, magnify the absorption rate of the bacteria; those deep breathes taken to clear the lungs are actually filling them with contaminants.

The inside of a shower head is a perfect breeding ground for bacteria, offering a moist, warm, dark haven where bacteria can form sticky "biofilms" that allowing them to breed.


"While chlorine bleach is almost universally thought of as a one-stop shop for killing harmful bacteria, using it to clean shower heads in the study had almost the opposite effect. In Denver, one shower head was cleaned with a bleach solution in an attempt to eradicate it. Tests on the shower head several months later showed the bleach treatment ironically caused a three-fold increase indicating a general resistance of this type of bacteria to chlorine." --Wallet Pop

As far as cleaning, removing the shower head and washing with a stiff brush may offer some help, but it will not eradicate the bacteria once they have taken hold.

Researchers are quick to say that showers do not pose a health threat for most healthy people with a well-functioning immune system.  However people with HIV, a compromised immune system, or taking immune-suppressing drugs should avoid showers.

Researchers suggest the only solution is to replace shower heads more often.  Once or twice per year is optimal.  Metal shower heads are preferred over plastic ones, as metal is more resistant to bacteria growth.


Most importantly, each time you take a shower: let the water run for a several minutes with the bathroom ventilation fan running (and you out of the room) before stepping into the shower. The highest concentrations of bacteria are always found in the water that comes out of the shower during the first couple minutes of use.

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This article was originally featured on RioDancesOnTheSand.com, a blog for the thinking person... Written by Rio Denali, a 30-something with peculiar curiosities, who makes the observations that many of us avoid. Full of useful links and entertaining articles, it is a fun favorite for the intelligent reader. For more great articles like this, please visit RioDancesOnTheSand.com.