Nooo this is not it. Sebum is a fatty oil and it can't be cleaned with just water. Water does not wash away oil, it sits on it. The point of shampoo is to remove sebum. If you don't remove sebum, it just accumulates on your scalp and makes everything worse. People with seborrheic dermatitis have too much oil production which is why they get dandruff and need to wash frequently. The whole thing has to do with hormones that your body produces. That's why little kids pre-puberty never have dandruff or oily hair and don't have problems with shampoo until after puberty. All shampoos also have conditioning agents which are meant to moisturize your hair after. It's ok to experiment with milder shampoos if need be, but just not washing your hair...no