“Run your shower for a minute or so before you get in, otherwise you’ll get a face full of bacteria.” That’s the advice of microbiologist Norman Pace, who has had the unenviable task of analysing the film of microbes that builds up within shower heads at 45 sites in the US.

Pace and his team from the University of Colorado, Boulder, found significant loads of nontuberculous mycobacteria (NTM), particularly Mycobacterium avium, at levels 100 times as high as those found in drinking water.

M. avium is responsible for a type of pulmonary disease more prevalent than TB in developed countries, cases of which have risen in parallel with the rise in showering, says Pace. “For most people, taking a shower is not dangerous, but if you are immune compromised, such as the elderly or pregnant, it could be,” he says.

His advice is to not use shower heads made of plastic. “If it has little crusty deposits, throw the sucker away. Have a bath.”


NTM expert Joseph Falkinham of Virginia Tech in Blacksburg says this type of data is needed to prepare a risk assessment, but we also need to know how many NTM of each species and type are needed to cause disease. “That is unknown for humans and not well established for laboratory animals either,” he says.

Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0908446106