A Study of the Photolightening Mechanism of Blond Hair with Visible and Ultraviolet Light
September 2004
in “
International Journal of Cosmetic Science
”
TLDR Blond hair lightens more with visible light directly, while ultraviolet light lightens it after washing by damaging other hair parts.
The study explored how visible (VIS) and ultraviolet (UV) light contribute to the lightening of blond hair and found that they do so through different mechanisms. VIS light significantly lightens blond hair directly, whereas UV light only causes lightening after the hair is washed, suggesting UV light damages hair tissues other than melanin granules. Both types of light similarly lighten isolated melanin granules, but VIS light also destroys their structure, unlike UV light. The findings suggest that while melanin granules are equally sensitive to both VIS and UV light, blond hair is more sensitive to VIS light, and UV light's lightening effect is due to its preferential damage to hair tissues other than melanin, which becomes evident after washing.
