When I was about 19, I figured out you could soap up in the shower and Oh Yeah Baby....but the soap was down so I used shampoo instead and worked it for maybe 30 minutes solid.
By late that evening, I was the most scared I have ever been in my life before or since as my Modestly Endowed Unit pruned up and got all dry and scaly. I could scrape off dried skin for an hour and I really, really thought I had killed Little Stevie.
It was three days before He got back to normal and I've always kept shampoo to my top head only every since.
And we all lived happily ever after
The End