About Photo-Damage of Human Hair

This paper reviewed the knowledge about human hair photodamage and the proposed photodegradation mechanisms, highlighting several unanswered questions. It noted a lack of understanding of hair structural changes caused by different radiation wavelengths and controversies regarding sun exposure effects on various hair types. While explanations often focused on melanin type and amount, the absence of detailed knowledge about melanin structure and standardized methodologies for human hair studies hindered reaching a consensus.