The concept of water-only hair washing dates back hundreds of years. Our ancestors didn’t have man-made chemicals to wash their hair with; and instead they cleansed their bodies and washed their hair with rough brushes and good old hot water. This abrasion technique breaks up all the dirt and oil on our skin and in our hair and the hot water rinses it away. Chemically-enhanced shampoo on the other hand, strips not only the dirt and bad oils, but also the good oils, known as sebum. Without these natural oils, our scalp produces more sebum than it actually needs, which is what makes our hair greasy and oily.