A study from researchers at the University of Colorado at Boulder found that 30% of showerheads contained high levels of bacteria that can lead to lung infections. While the level of bacteria in most showerheads does not pose a serious threat to a healthy adult there is some risk to individuals with lowered immune systems.
Water filters are available for your showerhead that can filter out harmful bacteria as well as chlorine and other particles.
The bacteria found in your showerhead are not a major concern for generally healthy people, but using a shower filter still has substantial benefits. The softer water you get by removing the chlorine from your shower is better for your hair and skin and can even help increase respiratory health.