The facial red fluorescence of ultraviolet photography: is this color due to Propionibacterium acnes or the unknown content of secreted sebum?

Background/purpose: Red fluorescence of the face induced by ultraviolet light is thought to be due to Propionibacterium acnes . However, recently there are reports correlating this red fluorescence with the amount of facial sebum secretion. This study was performed to investigate the relationship between the areas of facial red fluorescence with culture results of P. acnes and the amount of sebum secretion. Methods: Nineteen patients with acne were included. P. acnes cultures were done on specimens obtained from areas with red fluorescence. In addition, the amount of facial sebum secretion and the skin surface pH (SSPH) were measured. Correlation analysis of these parameters and the culture results were performed with the image analysis data from the red fluorescence of the face. Results: P. acnes was cultured in 36.5% of cases. The correlation of the culture rate with the red fluorescence areas was not significant. After classifying the patients into high‐sebum and low‐sebum groups, there was a significant difference in the red fluorescence areas. In addition, the red fluorescence area correlated with the SSPH. Conclusions: The red fluorescence area showed a stronger correlation with sebum secretion than with the presence of P. acnes . This finding suggests that the red fluorescence is affected by sebum not just P. acnes .