A recent study by researchers at the University of Colorado—published in the Proceedings of the National Academy of Sciences—revealed that showerheads can act as incubators for biofilm, a bacteria-saturated goop that builds up over time and contaminates shower water with thousands of germs. As the water passes through a showerhead, it picks up the bacteria—as much as 100 times more bacteria than in water that has not touched biofilm—and sprays it directly on your body or sends it flying into the air to be ingested into your lungs.
The good news is that, for people with normal immune systems, biofilm poses little health risk. However, it's hard to not to have your shower ruined by thoughts of microscopic bacteria all around. To cut down on the bacteria in your bathroom, try switching from a plastic to a metal showerhead. Plastic can serve as a bacteria breeding ground.
Meanwhile, research has long suggested that the dirtiest place in your house isn't even in your bathroom—it's your kitchen sink. If your coffee mug has been sitting in your sink, it could be swarmed with hundreds of thousands of bacteria.
Unlike a showerhead, a dirty sink actually could make you sick. Cut down on the thriving bacteria in your sink by replacing the sponge frequently—or permanently. Dish rags dry faster than sponges and harbor less bacteria. Also, a rag can be machine washed in hot water to kill even more germs.
Consider making a switch to green cleaners.