Optical coherence tomography and reflectance confocal microscopy can be used to non-invasively to visualize deep into the skin. Using these techniques we can actually see changes in the structure of the skin and its cells.
This group of researchers with funding from La Roche Posay used the imaging techniques to compare the effect of UVB exposure on skin protected with a high SPF and UVAPF sunscreen and skin that wasn’t protected.
What they found was that doses of UVB that caused long-lasting erythema (redness) caused morphological changes in the skin. Changes observed were spongiosis (abnormal accumulation of fluid), microvesicles, sunburn cells, and blood vessel dilation. None of these were observed in skin that was protected by the sunscreen.
A minimal erythemal dose or MED is the amount of UV energy that causes long-lasting redness in the skin. Just 1 MED was enough to cause morphological changes and 2 caused significantly more. This also relates to SPF. An SPF of 2 would provide enough protection to protect an average population against 2 MEDs.
If reducing your risk of developing skin cancers and preventing photoaging are a goal of yours – this is a great reminder and justification to wear your sunscreen daily!
Antonio Gomes-Neto, Paula Aguilera, Leonor Prieto, Sophie Seité, Dominique Moyal, Cristina Carrera, Josep Malvehy, Susana Puig, Efficacy of a Daily Protective Moisturizer with High UVB and UVA Photoprotection in Decreasing Ultraviolet Damage: Evaluation by Reflectance Confocal Microscopy, Acta Dermato-Venereologica (2018), DOI: 10.2340/00015555-2736