We have studied the spectroscopic properties of hair (white, blond, red, brown, and black) under illumination with visible light, giving special emphasis to the photoinduced generation of singlet oxygen ( 1O 2). Irradiation of hair shafts (λ ex > 400 nm) changed their properties by degrading the melanin. Formation of C3 hydroperoxides in the melanin indol groups was proven by 1H NMR. After 532-nm excitation, all hair shafts presented the characteristic 1O 2 emission (λ em = 1270 nm), whose intensity varied inversely with the melanin content. 1O 2 lifetime was also shown to vary with hair type, being five times shorter in black hair than in blond hair, indicating the role of melanin as a 1O 2 suppressor. Lifetime ranged from tenths of a nanosecond to a few microseconds, which is much shorter than the lifetime expected for 1O 2 in the solvents in which the hair shafts were suspended, indicating that 1O 2 is generated and suppressed inside the hair structure. Both eumelanin and pheomelanin were shown to produce and to suppress 1O 2, with similar efficiencies. The higher amount of 1O 2 generated in blond hair and its longer lifetime is compatible with the stronger damage that light exposure causes in blond hair. We propose a model to explain the formation and suppression of 1O 2 in hair by photosensitization of melanin with visible light and the deleterious effects that an excess of visible light may cause in hair and skin.