Site-specific variations in cutaneous autofluorescence revealed by excitation-emission matrix spectroscopy

Background and Purpose Although cutaneous autofluorescence has been utilized for evaluation of skin conditions, there is a paucity of data on normal human skin autofluorescence and its dependence on anatomical site. The objective of this study is to use excitation-emission matrix spectroscopy to quantify and characterize skin autofluorescence at different body sites. Methods Ten anatomical sites from 30 healthy volunteers were measured with a double-grating excitation-emission matrix spectrofluorometer. Results For the 10 body sites evaluated, there were four overall patterns of autofluorescence: skin from the head and neck exhibits high superficial and low bilayer fluorescence; the dorsal forearm and dorsal hand have both low superficial and bilayer fluorescence; the upper inner arm and back have high superficial and intermediate bilayer fluorescence; while the palm and thumbnail have both high superficial and bilayer fluorescence. The corresponding fluorescence excitation-emission peaks for these patterns were as follows: head and neck, 3 peaks at 290-300/330-350, 360-380/460-485, and 380-420/610-630 nm; dorsal forearm and dorsal hand, 2 peaks around 295-300/345-360 and 385-395/460-485 nm; upper inner arm and back, 3 peaks around 295-300/335-355, 335-340/390-410, and 375-390/455-480 nm; palm and thumbnail, 3 peaks around 285-300/345-355, 335-345/390-410, and 365-390/450-480 nm. Conclusion Cutaneous fluorescence varies in distinct patterns according to anatomical site, due to the component fluorophores present, skin thickness, and the degree of melanization and long term sun exposure. These EEM patterns for normal skin should be accounted for when interpreting fluorescence signals from disease states and can also be used to guide the selection of optimal wavebands when applying this optical modality.