According to physical investigations on human hair, a correlation
exists between the amount of IHL and the moisture content in
the hair [26]. A reduction in the amount of lipids by solvent
extraction [27] and oxidative damage during chlorine bleaching of
wool [28] or during permanent waving of hair [29] favor the
diffusion of foreign materials into the fiber [30]. Photochemical
changes can occur in IHL as well as in hair protein and hair pigment
[31]. Hoting [32] have shown that the CMC lipids of hair fibers are
degraded more by visible light but also by UVA and by UVB light,