Hair’s dark strands go white because of a buildup of the same compound people use as an all-purpose bleaching agent, hydrogen peroxide, according to research findings published online in The FASEB Journal, a publication by the Federation of American Societies for Experimental Biology.

Scientists reached this conclusion when they examined cell cultures of human hair follicles and found that hydrogen peroxide increased when an enzyme the body produces decreased.

That enzyme, called catalase, separates hydrogen peroxide into its primary components—water and oxygen.

Scientists also found that hair follicles could not preserve their dark color because of low levels of other enzymes (MSR A and B) that defend against hair graying.

In addition, researchers noticed that the high amount of hydrogen peroxide versus the low amount of these enzymes stopped the production of another enzyme called tyrosinase. Tyrosinase sparks hair follicle production of melanin, the pigment that makes hair, skin and eye color dark.

“All of our hair cells make a tiny bit of hydrogen peroxide, but as we get older, this little bit becomes a lot,” said Gerald Weissmann, MD, editor-in-chief of The FASEB Journal. “We bleach our hair pigment from within, and our hair turns gray and then white. This research, however, is an important first step to get to the root of the problem, so to speak.”

Read more about what causes us to go gray here.