Chapter 38: Singlet Oxygen in Hair

The damage in hair properties (color, structure, elasticity) caused by light exposition is still not well understood. Hair is specially positioned and pigmented to protect against solar radiation, water and heat loss, also exerting an important role in visual perception. Melanins are the main hair chromophores, conferring more than a beautiful and wide scenario of colors and also exerting the protective role against solar radiation. However, under certain circumstances these pigments can engage in excited-state reactions, damaging itself and the surrounding tissues. In this chapter we will explain how singlet oxygen is generated and eliminated in hair emphasizing the effect of visible light. Starting with a review of hair composition in terms of proteins, structure and micro/macro-organization, we will exploit the main chromophores that are present, emphasizing the ambiguous role of melanins as potentially damaging (singlet oxygen generators) and protecting (singlet-oxygen suppressor) agents and the effect of visible solar radiation. Details of the molecules that are damaged by singlet oxygen in hair and some protection strategies will be given and discussed. Understanding the mechanisms of generating and suppressing singlet oxygen in hair is essential to create new technologies for hair products.