It is often claimed that Asian skin is different from Black or Caucasian skin. This claim is so persistent throughout Asia, particularly East Asia, that it leads one to think there must be a physiological basis for it. Recent reviews such as the keynote presentation by Tony Rawlings at the 2005 IFSCC Conference1 provide a good overview of potential differences, but before discussing these, it would be beneficial to compare human skin with animal skin first.
Pig (ear) skin is generally believed to be the best model for human skin2 since its skin penetration characteristics and many other physiological parameters are roughly the same, or at least not very different. Table 1 lists some of these physiological characteristics; based on this work, the authors concluded that “the results obtained (on pig ear skin) are similar to those of human skin, indicating the suitability of this porcine tissue as a model for human skin.”
Of course, skin is more than a series of external observations. As shown in Figure 1, the skin lipid composition (qualitative and quantitative) and its packing are important for optimal barrier function.3 Early work by Bouwstra et al. has indicated that pig skin exhibits liquid and hexagonal packing,4 yet the orthorhombic stratum corneum (SC) lipid packing phase has been identified as being critical to human skin barrier function.5 Nevertheless the barrier function of the two has been described as quite similar. In a recent review, Barbero and Frasch found that when the in vitro permeability of pig and human skin were compared, the correlation coefficient r was 0.88 (p < 0.0001) for the 41 compounds studied.6 They also found that the coefficient of variation of skin permeability (i.e., standard deviation divided by the average) was 21% for pig and 35% for human skin.
