Applying heat via a blowout enhances the hair and is the secret to making hair look particularly beautiful.

noli's read

Aesthetically, the heat from a blowout works by temporarily breaking and reforming the hydrogen bonds in the hair fiber to smooth it, which aligns the cuticles and allows for better light reflection. Surprisingly, an experimental comparative study conducted by Lee et al. (2011) in the *Annals of Dermatology* demonstrates that moderate blow-drying (at 15 cm with continuous motion) preserves the internal cell membrane complex of the hair better than passive air-drying, because prolonged moisture weakens the fiber structure. However, the idea that heat in itself is an absolute factor for embellishment is exaggerated. Physical structural analyses (such as the in vitro thermal study by Bories et al., 1984) prove that beyond a critical threshold situated between 140°C and 180°C, heat irreversibly denatures keratin. At these high temperatures, the cuticle cracks, which destroys the natural shine. There is no evidence that high heat provides any biological benefit; without the use of a heat-protectant product to diffuse the temperature, it causes deep dehydration of the fiber.

the sources

No named source held this one up — that absence is part of the verdict.