Background: Chemical hair straightening becomes popular for managing frizzy hair.
Keratin in hair care products can penetrate the cortex of the hair fiber improving
the mechanical properties of damaged fibers and promote a surface coating that
prevents or decreases water diffusion through the hair fibers. This may have beneficial
effects on the hair structure; however, the side effects and safety of this treatment
have not yet been completely evaluated.
Aims: To evaluate the efficacy and safety of chemical hair straightening application
on the hair shaft.
Subjects and Methods: Thirty female subjects older than 15 years with hair curl
types III–V were included. They were subjected to full history taking and dermatologic
examination of hair and scalp prior to and after application of chemical hair
straightener. To detect the presence of transverse fissures, split ends, or possible
side effects, the distal 3‐5 cm of hair fibers were cut before and after the last step
of chemical hair straightener application for light microscopy examination. Three
randomly selected samples were examined by transmission electron microscope.
Results: Chemical hair straightening led to significant decrease in the degree of hair
curl and increased hair smoothness and shine. The treated hair fibers showed significant
repair of the broken cuticle (P < 0.001), while no significant improvement was
observed regarding transverse fissures or split ends (P 0.60 and 0.74, respectively).
Conclusion: Although chemical hair straightening application has a beneficial effect
on hair shafts, some side effects may occur after. Hence, it is necessary to develop
a more safe tool.