Reduction of Hair Damage by Biomimetic Amino Acids and Wool Keratin Pretreatments

Hair care pretreatments may limit the structural changes caused by chemical, thermal, and ultraviolet (UV) damage. We examined whether biomimetic amino acid (AA) and wool keratin (WK) pretreatments reduced these forms of hair damage. Virgin black human hair fibers were treated with 1% (w/w) AA or WK, washed with sodium laureth sulfate, and then subjected to oxidative bleaching, flat-iron treatment, or UV irradiation. Cuticular morphology was examined by scanning electron microscopy (SEM) and graded using a damage score. Cortical ultrastructure was assessed by transmission electron microscopy (TEM), and the cortical void-like area fraction was measured by quantitative image analysis. Across the three exposure protocols, fibers pretreated with AA or WK showed more continuous cuticular coverage and lower SEM damage scores than non-pretreated fibers exposed to the same conditions. Their cortical matrices were also more continuous, and their cortical void-like area fractions were lower (adjusted p < 0.05). Together, these findings indicate a reduced severity of cuticular and cortical changes relative to the corresponding damage-only group.