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Impact of epidermal thickness on purpura from the pulsed dye laser
M Haedersdal1, N Bech-Thomsen, P Therkildsen
1Department of Dermatology, Bispebjerg Hospital, University of Copenhagen, Denmark.
Background And Objective:
To clarify whether epidermal thickness is of importance to the purpuric reaction from treatment with the pulsed dye laser (PDL).
Study Design/Materials And Methods:
Fifteen fairly pigmented volunteers were laser treated in two test regions of varying epidermal thicknesses: normal buttock skin and ultraviolet B (UVB)-exposed buttock skin. Laser treatments were performed with the flashlamp-pumped PDL (585 nm). Fluences ranged from 3-6.5 J/cm2, spot size was 7 mm, and each volunteer received at least six fluences in each treatment region. Assessment of the response was based on clinical evaluation (threshold dose to purpura 10 minutes and 1 day after treatment) and skin reflectance-evaluated redness (1 and 6 days, 2 and 6 weeks after treatment).
Results:
The total epidermal thickness differed between the unexposed buttock skin (median, 72.7 microm) and the UVB-exposed buttock skin (87.2 microm) (P < 0.01). There was no correlation between the epidermal thickness and the threshold dose to induce purpura 10 minutes and 1 day after laser exposure. Skin reflectance revealed no correlation between the epidermal thickness and the skin reflectance evaluated redness on 1, 6 days, and 2 weeks postoperatively. A dose-response relation was seen within the two test regions; 6 weeks after laser exposure, there was no remaining laser-induced skin redness.
Conclusion:
The epidermal thickness is unimportant to the purpuric reaction after PDL treatment.