The Reactivity of Human Hair. A Review

Investigation of nail permeation enhancement by chemical modification using water as a probe

“…Amino acid derivatives: the molecule chosen for these studies was N‐(2‐mercaptopropionyl) glycine (MPG, Tiopronin), which has the structure shown in Figure 1. MPG has a molecular weight of 163.20, and is classified as a hepatoprotectant, mucolytic agent, and antidote to heavy metal poisoning,5 and does not infringe on the patent of Sun et al2 Mercaptan compounds have been established to reduce keratin in human hair via a sequence of two reversible, nucleophilic displacements 6,7. High concentrations of the mercaptan and alkaline pH favor the forward reaction due to the increased formation of the mercaptide anion required for reduction 8,9…”

“…10 The zinc (ZnPTO) and sodium (NaPTO) derivatives of pyrithione (Figure 2) possess fungicidal activity and ZnPTO is commonly used in antidandruff preparations. Compounds containing a SH group are themselves oxidized while reducing disulfide linkages in nail keratin 6,7. For PTO, such self‐oxidation would result in the formation of the dimer (dipyrithione).…”

“…Terpenes are known to be effective skin penetration enhancers, and menthone, in particular, has been found to enhance penetration of several different drugs across skin 11,12. 1,4‐Dithiothreitol (containing two SH groups), has been shown to be a particularly effective reducing agent, because this molecule can undergo rapid autocleavage during the reduction process to form a sterically favored cyclic disulfide as the end product 7. To investigate the effect of multiple SH groups on reduction of disulfide bonds, meso‐2,3‐dimercapto succinic acid (Succimer) was investigated.…”

Hair cuticle differences between Asian and Caucasian females

“…Little information is available on how scalp hair cuticles differ between Asians and Caucasians 1–3 . The aim of this study was to clarify precisely cuticle differences between these two groups.…”

Ethnic characteristics of eyelashes: a comparative analysis in Asian and Caucasian females

“…Human hair is categorized into three major distinct groups according to ethnic origin: Asian, Caucasian and African 1 . Although the protein and amino acid compositions of scalp hair are similar in different races, hair physical properties are not identical 2–4 . Compared with the scalp hair of Caucasians as determined by cross‐sectional electron microscopy, that of Asians is thicker and has a more circular geometry, and hair shafts are straighter and more cylindrical 3,5 .…”