earticle

영어

Purpose: We aimed to investigate the relationship between hydrogen peroxide (H₂O₂) concentration, the number of non-thermal bleaching sessions, and their effects on hair lightness and cuticle damage. This study seeks to establish a scientific foundation for safer bleaching protocols, particularly for fragile or chemically treated hair. Methods We conducted repeated non-thermal bleaching using 3%, 6%, and 9% H₂O₂ on a total of 46 human hair tresses. Each concentration group included three sets of five tresses (total n=45), and one untreated virgin hair tress was used as a control. Hair lightness was measured using a standardized 20-level chart, and cuticle damage was assessed via FE-SEM (× 2,000). Damage types—lifting, fragmentation, and dissolution—were classified morphologically. Results We observed that as H₂O₂ concentration and bleaching frequency increased, hair lightness rose, but so did the severity and extent of cuticle damage. Notably, the 9% group reached Level 19 lightness by the third session but exhibited widespread cuticle dissolution. Conversely, the 3% group reached only Level 17 after five repetitions and showed milder damage. At similar lightness (Level 17), the 6% group showed more severe cuticle degradation than the 3% group. This reveals that concentration plays a more critical role than frequency in determining damage severity. Conclusion: We confirmed that equivalent levels of lightness can mask significantly different levels of cuticle integrity depending on the bleaching protocol. Relying solely on lightness as a damage indicator is insufficient. Our study highlights the importance of morphological analysis of the cuticle to assess structural damage and supports the use of low-concentration H₂O₂ with controlled repetition in professional settings. We propose further research using image quantification and diverse hair types to improve generalizability and reproducibility.