Why gray? Why salt & pepper?

Scientists are working to unlock the mysteries of gray hair:

What’s intriguing about skin and hair cells is that while most of the body’s cells are programmed to turn themselves off when exposed to harmful stresses, certain skin and hair cells are much tougher. A few years ago, Harvard researchers reported that graying occurred when the stem cells that govern hair coloring lost their hardiness and shut down. The hope is that research into those cells may ultimately lead to treatments for melanoma, a skin cancer that can be fatal.

One of the many mysteries of gray-hair research is why some people have salt-and-pepper hair. “If it was purely based on one’s antioxidant system or the ability to handle oxidative stress, then you still have to explain why some follicles can produce perfectly pigmented hairs in a sea of white hairs,” said Desmond J. Tobin, associate dean of research and knowledge transfer at the University of Bradford.

Dr. Tobin notes that the skin is the only major organ that is directly exposed to environmental stress outside the body and the changing environment inside the body.