In order to investigate the relationship between breaking stress and whiteness in a bleaching treatment with laccase, hair samples from three biogeographically distinct populations were characterized by various chemical and physical techniques. Factors affecting whiteness and breaking stress were investigated by attenuated total reflection infrared spectroscopy, atomic absorption spectroscopy, X-ray diffraction and scanning electron microscopy. The results reveal that whiteness and breaking stress after bleaching are primarily influenced by the diversity of concentration of metal ions and functional groups in the hair. The hair samples with lower content of metal ions obtain better whiteness and higher stress retention. The presence of OH functional group increases the final whiteness of the hair sample, while lack of that not only decreases the whiteness but also leads to more stress loss. In addition, the presence of the C-C functional group also decreases the whiteness.