My hair grew back fine. I didn't let this recent cowashing experiment continue on long enough for my hair to be noticeably thinner. I think in my case the extra manipulation required to get my hair clean is the culprit. When I use shampoo, I gently massage it for only a few seconds into the scalp area. I don't massage the length. The suds travel down my length as I'm rinsing it out and that gets my length very clean without any dryness. It works for me.