Most consumers are aware that exposure to UVB and UVA radiation accelerates skin aging and increases the risk of skin cancers such as melanoma. Therefore, agents for protecting the skin against UV radiation are not rare guests in consumers’ cosmetic bags; however, fewer individuals have awareness or concern that their hair is also affected by UV radiation.
Scientific and popular literature associate UV hair damage with dryness, increased breakage and split ends, lower luster and increased surface roughness 1—and all of these changes do not appear immediately or all at once in the same place. UVB radiation affects hair approximately 5 µm beneath the surface layer.2 For healthy hair, this is mainly the cuticle layers. For hair that has already been significantly damaged, i.e., due to intense bleaching and heat treatments, cuticles may already be missing. In this case, the cortex would be affected by UVB as well. UVA radiation is less intense but is capable of deeper penetration, thus the entire cortex may be affected.
Different hair properties can change at different rates. As such, in order to test preventative hair care treatments, sensitive techniques are required to detect low levels of damage that have not yet been translated into measurable changes in the mechanical properties of hair.