Diverse causes of extrinsic damage to the hair shaft have been documented and can be roughly divided into physical and chemical causes. Chemical causes of hair damage include bleaching, hair dyeing, and perming.


The goal of this study was to investigate differences in patterns of serial damage in Asian, White European (WE), and African hair after chemical stress imposed by straightening and coloring treatments.


Hairs were divided into control and treatment groups (straightening, coloring, and a combination of straightening and coloring). At 24 hours after the final treatment, patterns of hair damage were evaluated using transmission electron microscopy (TEM) and lipid TEM. Grades of hair cuticle and cortex damage were evaluated by three dermatologists.


In the TEM examination, the cuticle of Asian hair proved to be resistant to damage caused by straightening treatments, whereas the WE hair cuticle and cortex were relatively susceptible to stress imposed by coloring treatments. In the combination treatment of straightening and coloring, African hair emerged as the most resistant to stress. In the lipid TEM examination, no notable differences in cell membrane complex damage were observed among the three groups of hairs.


The present study suggests that WE hair is relatively susceptible and African hair is more resistant to chemical stresses, such as those imposed by straightening and coloring.