Shower heads are a perfect environment for a dangerous bacteria related to tuberculosis. Mycobacterium avium thrives in wet, dark environments and can invade the lungs when sprayed from a shower head.

While healthy people are not at risk, the microbes can be dangerous for pregnant women and people with weakened immune systems, says the National Academy of Sciences.

“Unfortunately, shower heads have nooks and crannies that make
them hard to clean. Products with bleach can temporarily remove many
microbes, but they just grow back,” researcher Leah Feazel said.

Feazel recommends changing shower heads two to four times a year or switching to a metal shower head and letting the water run a few minutes to flush out pathogens. Bathing is a option because the water droplets are too large to penetrate the lungs, she said.