A. This is an excellent question. Hair spray is traditionally a liquid that is aerosolized for application to the hair as a fine droplet film to increase the ability of the hair to stay in place. Many years ago shellac-like chemicals were used, which did not wash out with shampoo. There are also reports in the literature in the 1960s of lung disease, known as thesaurosis, resulting from the use of hair spray; however, modern formulations are safe for use and are designed for shampoo removal to a greater or lesser degree.