Paradoxically it’s greasy hair that could benefit the most from giving up shampoo. The theory behind the ‘no-poo’ method is that shampoo strips the hair of its natural oils, which prompts the scalp to generate more oils to replace them. This results in oil overload – greasy hair – which we then attempt to ‘fix’ with more shampoo. It’s a vicious circle and quite a brilliant coup for the shampoo industry, because the more shampoo you use, the more you need to use and the more frequently you need to use it.