An evaluation of the course of facial sunscreen coverage and sustainability over an 8-hour workday among outdoor workers.

Background Reapplication of sunscreen every 2 hours is recommended, especially after swimming, sweating, or working outdoors. However, the sustainability of sunscreen during the workday among outdoor workers is still unclear. Objective To evaluate the course of facial sunscreen coverage and sustainability over an 8-hour workday among outdoor workers. Materials and methods This open-label trial included 20 healthy subjects who spend at least 80% of their workday outdoors. All volunteers applied 2 mg/cm2 of provided broad-spectrum sunscreen mixed with the invisible blue fluorescent agent to all parts of their face in the morning. A VISIA-CR camera was used to capture facial fluorescence intensity every 2 hours, and digital image analysis software was used to quantify fluorescence intensity at six areas of the face at each time point for 8 hours. Results Sunscreen coverage declined most rapidly during the first 2 hours with a mean reduction of 18.31%. By the end of the 8-hour study workday, the mean decrease in sunscreen coverage was 31.63% (range: 17.39%-45.29%). Conclusion Reapplication of sunscreen is essential among outdoor workers. After 4 hours, the amount of sunscreen remaining on the face may not be sufficient for protecting the skin from harmful ultraviolet radiation.