This paper examines some of the existing methods for colouring the hair and skin using natural material (such as henna) and proposes a parallel technology that exists in the dyeing of wool and fabrics to extend the colour range. Many of the listed plants and their derivatives are not found in Annex IV of the Cosmetic Directive and may not be used as colours, however, they do have other properti...

There's little study-based evidence of anyone getting gray hair from dyeing his or her hair over and over again. However, some studies have suggested that heavy use of hair dye might cause cancer [2] in some people (both in people who are dyeing their hair, and in colorists whose livelihood depends upon providing the coloring process). The connection to cancer needs more research, but it's enou...