Effect of UV on SC lipid packing. Exposure to UV leads to disruption in the lipid organization in the skin. The red colours in the infrared image indicate a shift to “looser” packing of lipids, which increases with UV exposure time. Infrared imaging is a powerful tool to study the molecular organization of the skin non-invasively.
The in vivo SPF test is widely used to evaluate how well sunscreen products protect the skin from erythema (redness and inflammation). However, UV exposure does more than cause a sunburn. Scientists at TRI Princeton have shown that UV exposure can alter the internal structure of the stratum corneum (SC), thus affecting the overall barrier function of the skin. This insight gives rise to a new kind of UV protection study and evaluation of new benefits from sunscreen products.
TRI protocols for the measurement of SC lipid barrier organization, using FTIR spectroscopy, are used to measure UV effects. Our methods clearly show an increase in lipid disorder with increasing UV exposure and can be used to screen sunscreen effects. Our methods can be applied to ex-vivo skin and to in vivo skin in pre-clinical or clinical tests.