Daily shampooing became the norm in the USA in the '70's and '80's, but shampoo was never intended to be used every day
Synthetic shampoos were only introduced onto the market in the 1930’s and it was available for almost 40 years before daily shampooing of hair became a norm in the USA.
It was only in the 1970’s and 1980’s that Americans began washing their hair on a daily basis.
Now, however, there is widespread belief that it is, in fact, very bad for the hair and the scalp to shampoo every day because shampoo removes the natural oils (sebum) produced by the scalp.
This causes the scalp to produce more oil to compensate, and a vicious circle ensues.
Some dermatologists say that it is best to gradually increase intervals between washes to allow the sebaceous glands to produce at a slower rate, thereby normalizing the body’s natural rate of sebum production.
It is not certain why the American public started the practice of daily shampooing, because even early shampoo manufacturers made it clear that it should not be a daily practice.
According to an article published in the ‘New York Times’ in 1908, “hair specialists recommend the shampooing of the hair as often as every two weeks, but from a month to six weeks should be a better interval if the hair is in fairly good condition.”