Hair coloring and bleaching can permanently break down hair protein and temporarily change its properties.
October 2015 in “Cosmetic Dermatology” Hair straightening changes hair structure and can cause damage if done wrong, but improvements in the methods are expected to continue.
3 citations,
January 2021 in “ScienceAsia” Using an enzyme and keratin treatment can significantly repair and strengthen damaged hair.
11 citations,
April 2022 in “Biophysical Journal” Disulfide bonds in keratin fibers break more easily under stress, especially when wet, affecting fiber strength.
May 2024 in “International Journal of Cosmetic Science” Disulfide bonds are crucial for hair's strength, especially when wet.