Scientists may have figured out why hair actually turns gray, and their finding may open the door to new anti-graying strategies.

New Research shows that hair turns gray as a result of a chemical chain reaction that causes the hair to bleach itself from the inside out.

The process starts when there is a dip in levels of an enzyme called catalase.  That catalase shorfall means that the hydrogen peroxide that naturally occurs in hair can't be broken down. So hydrogen peroxide builds up in the hair, and because other enzymes that would repair hydrogen peroxide's damage are also in short supply, the hair goes gray.

Putting the brakes on that chemical chain reaction "could have great implications in the graying scenarios in humans," write the researchers, who included Karin Schallreuter. a professor clinical and experimental dermatology at England's University of Bradford.

The study appears online in the FASEB Journal; the FASEB is the Federation of AMerican Societies for Experimntal Biology.

Senile graying of human hair has been the subject of intense research since ancient times. Reactive oxygen species have been implicated in hair follicle melanocyte apoptosis and DNA damage.  Ere we show for the first time by FT-Raman spectroscopy in vivo that human gray/white scalp hair shafts accumulate hydrogen peroxide (H2O2) in millimolar concentrations.  Moreover, we demonstrate almost absent catalase and methionine sulfoxide reductase A and B protein expression via immunofluorescence and Western blot in association with a functional loss of methionine sulfoxide (Met-S=O) repair in the entire gray hair follicle. Accordingly, Met-S=O formation of Met residues, including Met 374 in the active site of tyrosinase, hte key enzyme in melangenesis, limits enzyme functionality, as evidences by FT-Raman spectroscpy, computer simulation, and enzyme kinetics, which leads to gradual loss of hair color.  Notably, under in vtro conditions, Met oxidation can be prevented by L-methionine.  In summary, our data feed the long-voiced, but sufficient proven, concept of H2O2-induced oxidative damage in the entire human hair follicle, inclusive of the hair shaft, as a key element in senile hair graying, which does not exclusively affect follicle melanocytes. This new insight could open new strategies for intervention and reversal of the hair graying process. - Wood, J.M.,Decker, H., Hartmann,H.,Chavan,B., Rokos,H., Spencer,J.D., Hasse,S., Thornton,M.J. Shalbaf,M.,Paus,R., Schallreuter,K.U. Senile hair graying: H2O2-mediated oxidative stress affects human hair color by blunting methionine sulfoxide repair.

Article by Mirand Hitti - WebMD News Reviewed by Louise Chang, MD Feb 25, 2009.