Most shampoos do a decent job of cleaning the hair shaft. But if you keep dealing with flakes, an itchy scalp, or that persistent oily feeling, the problem likely isn't your hair. It's what's happening underneath.

Most shampoos do a decent job of cleaning the hair shaft. But if you keep dealing with flakes, an itchy scalp, or that persistent oily feeling, the problem likely isn't your hair.…

We spend a lot of time thinking about our hair: the right conditioner, the right oil, the right treatment. But the thing that actually determines how your hair looks and grows? It…