Thermal cycling with focused airflow prevents α-keratin denaturation and structural damage in human hair in Korea:an ex vivo study
- Author:
Tae-Rin KWON
1
;
Doohyun HAN
;
Jungwook KIM
;
Hyoung Jun KIM
;
Byung Ho YOON
;
Dong Wook MOON
;
Jungkwan LEE
;
Kwang Ho YOO
Author Information
- Publication Type:Original article
- From: Medical Lasers 2025;14(3):168-174
- CountryRepublic of Korea
- Language:English
-
Abstract:
Background:Excessive heat from household styling devices denatures α-keratin, damages the cuticle, and degrades overall hair quality. Conventional blow-dryer temperatures often exceed 90°C, surpassing the safety threshold for keratin fibers. To determine whether combining focused airflow with rapid thermal cycling (peak temperatures ≤60°C) attenuates multiscale hair damage compared with continuous-heat drying.
Methods:Human-hair tresses were assigned either to a focused-flow dryer operating in alternating cool/warm cycles or to a continuous-heat mode. Jet characteristics were quantified using planar particle-image velocimetry, and airflow temperatures were recorded using micro-thermocouples. Post-treatment analyses included scanning electron microscopy (cuticular surface roughness, Ra), single-fiber tensile testing, crosssectional densitometry (fiber compactness), and confocal Raman spectroscopy (α-helix/disulfide bond integrity).
Results:Thermal cycling with focused airflow increased the central-core flow fraction from 37% to 64% and confined hair-surface peaks to 58°C-60°C. Alternating hot-cold drying reduced cuticlar surface roughness by approximately 7.3%, whereas continuous hat air drying increased roughness by 4.9%. Ultimate tensile strength was essentially preserved (–0.4%) under cycling but fell by 9.4% with uninterrupted heat (p = 0.003).Compactness loss was limited to 33% vs. 50%, and the S-S disulfide bond (~510 cm –1 )/C-H bending vibration band (~720 cm –1 ) ratio decreased by only 11% (vs. 19% under continuous heat).
Conclusion:Brief cooling intervals, when paired with a confined airflow, effectively prevented α-keratindenaturation and structural collapse. These findings support a clinically relevant approach to preserving hairfiber integrity during routine hair care and styling.
