I tried this when it made the HN rounds about a year ago. My results were over about three months and my primary reason was to assist treating moderate eczema. I stopped using all soap and shampoo and just stuck with hot-as-hell water. My skin did get better, but after about two months my hair began to naturally dread. After I looked back on my notes of this endeavor I decided to use some scent-free shampoo to prevent dreads. I use soap to clean up when I finish painting/working on a car or other dirty project. I also use it before I prepare food for my family and friends. My hair did never really 'feel' right, much more like a dogs fur than clean hair. It didn't smell bad it just felt different and didn't behave.

The interesting thing that came out of my tracking this impromptu 'shower log' of no soap use - I was able to correlate my severe eczema outbreaks with inhaling allergens. In my case, breathing in pine dust & glue particulate causes outbreaks. I now wear my painting respirator 75% of the time in the shop and have very few incidents.