Also, hydrogen peroxide undergoes photochemical reduction yielding highly reactive hydroxyl radicals (OH.) and hydroxyl ions (OH-) mainly by the Haber-Weiss reaction. Hydroxyl radicals are capable of bleaching constitutional melanin and cause membrane lysis through lipid peroxidation reactions. Hydroxyl ions increase the pH in the epidermis, and as a consequence glutathione reductase activity is increased in patients with vitiligo compared to controls. Based on these new results, together with the previously reported calcium transport defect, a new hypothesis has been formulated for the pathogenesis of vitiligo.