Dry shampoos carry several benefits for certain patients, but it's not a replacement for liquid shampoo. Here is the advantage.
Dry shampoos were very popular and actually developed prior to the modern liquid shampoos. They were used when warm running water was not available in all homes and most women wore long hair styled into a variety of buns. The advantage of the dry shampoo was preservation of the hairstyle and odor control. Dry shampoos are used today for much the same reason.
With the new popularity of dyed hair, dry shampoos prolong the life of the hair color since permanent and semipermanent dyes fade with water contact. The use of elaborate hair extensions, discussed previously, also last longer when hair water contact is avoided.
Dry shampoos are dusted on the scalp and are a fragranced powder. The powder absorbs sebum and is then brushed out of the hair. It does not replace shampooing, but can prolong the interval between shampooing. Dry shampoos are not recommended for persons with seborrheic dermatitis or other scalp infections. Dry shampoos do appear to give the hair more body, however, as the unremoved particles increase friction between the hair shafts allowing the hair to stand further away from the scalp appearing more abundant. Many mature women who do not wish to have a wet head after shampooing prefer dry shampoos, since their sebum production is reduced and the dry shampoo can be used in between visits to the hair salon.