Your showerhead may deliver more than a refreshing spray of water. New research suggests disease-causing bacteria hide out inside showerheads, hitching a ride to your face and body inside water droplets.

The grimy results come from genetic tests run on samples from 45 showerheads in homes, apartment buildings and public places from nine U.S. cities in five states: New York, Illinois, Colorado, Tennessee and North Dakota.

About 20 percent of the showerhead swabs harbored significant levels of Mycobacterium avium, bacteria linked to pulmonary disease that most often infects people with compromised immune systems, said lead researcher Norman Pace of the University of Colorado, Boulder.

Pace and colleagues found that M. avium and related pathogens were clumped together in slimy biofilms that coated the insides of the showerheads at more than 100 times the levels found in municipal waters that are the origins for the showers' water.

Once the pathogen-laden water spurts from showerheads, the bugs can suspend in the air where showering individuals can easily inhale them into the deepest parts of the lungs, Pace said.

For those with immune-compromised systems, Pace recommends changing out your showerhead regularly. Sufficiently cleaning showerheads may prove difficult as they are full of hard-to-reach nooks and crannies. While chlorine-bleach products may remove some bacteria, mycobacteria are resistant to chlorine. He added that microbes attach more easily to plastics, so an all-metal showerhead might be a good investment for the immune-compromised.

At the end of the day, Pace doesn't recommend steering clear of the shower. "It's like anything else — there is a risk associated with it," Pace said

The study, detailed in the Sept. 14 online edition of the journal Proceedings of the National Academy of Sciences, was funded by the Alfred P. Sloan Foundation and the National Institute of Occupational Safety and Health.