Mice without a certain gene have more harmful molecules in their hair color stem cells when their hair is growing, which might be why these cells get damaged.

When a certain gene is turned off in mice, it damages the stem cells that give hair its color—but not the regular color-making cells—so the hair gradually loses pigment and turns gray or white.

When a certain gene is turned off in hair color cells in mice, their fur starts to gray early because the cells die off — but the ones that survive can still make pigment just fine.

Giving an antioxidant called NAC in drinking water helped slow down hair greying in mice that were genetically prone to it, possibly by reducing harmful molecules in their bodies.