My daughter learned that lesson when she was around 3 years old, the first time we let her shower by herself. She washed her long hair with her wash cloth. It was a miserable night for everyone that night.

But yes, I love discovering something that you feel is something you should have already known. I had a realization in my 30s that maybe not everyone gets little sores all over their body all the time... I changed my body wash and the problem went away. I feel like most people would have known that was a problem much sooner.