The personal care industry has focused heavily on how UV damages skin, but not specifically on how UV affects the mechanical integrity of skin. At least, according to Guy K. German, an assistant professor Binghamton University.
As a recent EurekAlert! explained, a new study by Zachary W. Lipsky, a biomedical engineering Ph.D. candidate at Binghamton University overseen by German, assistant professor of biomedical engineering, sought to answer just that. More specifically, to answer what kind of UV radiation is the worst for skin, and how exactly the sun damages it.
UV Types and Damage
The study, to be published in the December 2019 Journal of the Mechanical Behavior of Biomedical Materials, sought to quantify how exposure to different UV ranges and doses impacts the mechanical and structural properties of human stratum corneum (SC).
According to the article abstract, mechanical testing revealed irradiation of isolated human SC to UVA (365 nm), UVB (302 nm), or UVC (265 nm) light at levels of up to 4,000 J/cm2 altered the elastic modulus, fracture stress, fracture strain and work of fracture.
For equal incident doses, UVC degraded SC the most, although after accounting for reflectance and transmittance, a general scaling law emerged that indicated no one UV range was more damaging than another; instead, the magnitude of the absorbed UV energy dictated the damage.
Additional structural studies were then carried out to understand the cause of this mechanical degradation. Also according to the article abstract, it appeared that UV absorption scaled with the spatial dispersion of desmoglein 1, a component of corneocyte cell-cell junctions, away from intercellular sites. Or, put another way by EurekAlert, UV weakened the bonds between cells in the SC by affecting the cells that aid in cohesion.
For more information, see the Journal of the Mechanical Behavior of Biomedical Materials.