Unfiltered shower water can contain an array of chemicals like chlorine as well as bacteria and fungus from the shower head.
The skin is much more than just a covering for the body. It is the largest organ and is responsible for important functions like vitamin d creation and synthesis. It also has the ability to absorb much of what it comes in contact with and we are learning that it has its own unique and important microbiome!
This is why topical magnesium oil works so well and why sunlight is so important.
It is also why a shower filter is so vital:
Chlorine is effective at killing pathogens in the water, but the properties that make it able to do this may affect the skin microbiome and the delicate balance of bacteria on the skin.
 
We May Absorb More Chlorine Through Showering than Through Drinking Water