Some interesting ideas are coming out of further investigations of the biochemistry of greying hair: "Intriguingly, the continuous melanin synthesis in the growing (anagen) hair follicle generates high oxidative stress. We therefore hypothesize that hair bulb melanocytes are especially susceptible to free radical-induced aging. ... We found evidence of melanocyte apoptosis and increased oxidative stress in the pigmentary unit of graying hair follicles. The 'common' deletion, a marker mitochondrial DNA-deletion for accumulating oxidative stress damage, occurred most prominently in graying hair follicles. ... We conclude that oxidative stress is high in hair follicle melanocytes and leads to their selective premature aging and apoptosis. The graying hair follicle, therefore, offers a unique model system to study oxidative stress and aging and to test antiaging therapeutics in their ability to slow down or even stop this process."