Oxidized hair can naturally regain strength and stability over six months.
Hair coloring and bleaching can permanently break down hair protein and temporarily change its properties.
13 citations,
March 2019 in “Journal of cosmetic dermatology” Heat damages hair, with Asian hair losing more protein than Caucasian hair.
28 citations,
December 2011 in “Biocatalysis and biotransformation” PDI helps restore over-bleached hair's strength and structure by attaching special peptides.
March 2010 in “Cosmetic Dermatology” Hair straightening methods have advanced to improve effectiveness and reduce damage, but still rely on heat and chemicals.