Advocates argue that commercial shampoo is an unnecessary expense and may contain harmful ingredients.
[4] From a clinical point of view, "the main purpose for a shampoo is to cleanse the scalp", not to "beautify the hair".
[1][6] Following a 2007 radio interview with Matthew Parris (a Times columnist "who hadn't shampooed for more than a decade"), Australian radio presenter Richard Glover challenged his audience to try going without shampoo for six weeks.
[7] Some proponents argue that by removing the natural oils (sebum) produced by the scalp, commercial shampoo creates a vicious circle of increased oil production and more frequent hair washing,[2][8] which can take up to six weeks to break.
[6] Alternatively, the hair can be washed with baking soda, followed by an acidic rinse such as diluted apple vinegar.