The cuticle of Chinese hair is more sensitive to physical and chemical treatments
The cuticle is the hair’s first line of protection against external stresses
such as brushing and combing, which cause the hair to age.
Studies of Chinese and Caucasian hair, both natural and chemically
treated, found that the cuticle of Chinese hair is broken down into smaller particles than that of Caucasian hair. This would appear to be due to geometric characteristics rather than ethnic origin.
The two geometric characteristics of human hair — the distance between scales and the angle of the scales — are directly related to the diameter of the hair, not to ethnicity. Since Chinese hair is thicker on average, its scales
are closer together and more angled. In addition, the cuticle of Chinese
hair appears to be more sensitive to chemical treatments particularly
straightening, as compared with Caucasian hair .
The degree of curl influences how hair behaves under different treatments
The properties of curly hair from different countries were assessed using a laser scan micrometer, tensile tests and 2D electrophoresis. The results showed that the characteristics of the hair are affected by the degree of curl. For example, the curliest hair tends to be the most fragile. In addition, differential scanning calorimetry (DSC) and 2D electrophoresis have shown that the thermal behaviour and protein markers of hair differ depending on its origin. These variations could potentially have an impact on how hair responds to treatments .
African hair is drier
Infrared microspectroscopy was used to measure cross-sections of hair
taken from the heads of Caucasian and African American subjects. An assessment of lipid content showed that Caucasian hair often contains lipids located inside the medulla and, to a lesser extent, within the cuticle. African hair, on the other hand, has a lower lipid content and a different distribution pattern: there are no lipids in the medulla and very irregular distribution within the cuticle. This results in drier, more fragile hair that is harder to style .
 Galliano A, et al. Resistance of human hair cuticle after a shaking
process in wet conditions: comparison between Chinese and Caucasian hair. Int J Cosmet Sci. 2010; 32: 356–368
 Porter CE, et al. The behavior of hair from different countries.
J Cosmet Sci. 2009; 60: 97–109
 Kreplack L, et al. Profiling lipids across Caucasian and Afro-American
hair transverse cuts, using synchrotron infrared microspectrometry.
Int J Cosmet Sci. 2001; 23: 369–374