Sunscreen remanence on the skin: a noninvasive real time in vivo spectral analysis assessing the quenching of specular ultraviolet A light reflectance.

BACKGROUND

Under specific light illumination, particularly ultraviolet radiation (UVR), the skin produces both specular light reflectance and, possibly, specific fluorescent emission. A quenching effect of fluorescence is observed following the application of sunscreens active against UVA radiations.

AIMS: To assess noninvasively in a real-time process, the potential sunscreen remanence/substantivity after application on the skin.

METHODS

The Visiopor® device was used in a real-time procedure after application of sunscreens to the skin. A quenching effect of follicular fluorescence due to bacterial porphyrins was evaluated at 30-min intervals. The Visioscan(®) device was used as a distinct UVA emitter in a control procedure of spectral analysis of specular UVR emission and reflectance by dermal fibers.

RESULTS

Under UVA-1 irradiations, facial skin produced different patterns of specular UVR reflectance and fluorescent emission as well. The porphyrin-related follicular fluorescence was instantly abated by UVA blockers present in suncare products. The potential sunscreen remanence/substantivity was assessed by the follicular and interfollicular fluorescence recurrence all along the next hours.

CONCLUSIONS

All UVA blocker-containing suncare products exhibited a similar overall quenching effect on porphyrin-enriched facial hair follicles and dermal fibers. This effect lasted for a few hours. Differences in the fluorescence recovery were likely related to the amount in suncare application and the nature of the formulation components.