Chapter 15 519 expect that such thin layers could provide any intervention against the extremely high temperatures encountered during heat styling. UV adsorbers may be included in formulations, but with seemingly little efficacy. Nonetheless, it may still be gratifying to learn that conventional products do not indeed aggravate this occurrence. Figure 19. Color fade in permanently dyed hair as a function of treatment with a straightening hot iron Figure 20. Color fade in permanently dyed hair as a function of hair condition