Human hair and skin become soiled due to its contact with the surrounding environment and from the sebum secreted by the scalp.
The soiling of hair and skin causes it to have a dirty feel and an unattractive appearance. Shampooing cleans the hair by removing excess soil and sebum. However, shampooing can leave the hair in a wet, tangled, and generally unmanageable state. Once the hair dries, it is often left in a dry, rough, lustreless, or frizzy condition due to removal of the hair's natural oils.