Skin pigmentation kinetics after UVB exposure.
There have been few previous studies of the kinetics of pigmentation following ultraviolet B (UVB) exposure, and these have included only fair-skinned persons. The current study investigated pigmentation increase to steady state and fading in 12 Scandinavians and 12 Indians/Pakistanis. Over a period of 3 weeks the subjects were UV-irradiated 6 times on the right side of the back and 12 times on the left side using a Solar Simulator and narrowband UVB with equal sub-Minimal Melanogenesis Doses (individually predetermined). Pigmentation was measured from skin remittance at 555 nm and 660 nm (allowing correction for erythema). The absolute pigmentation increase was independent of pre-exposure pigmentation, therefore the percentage pigmentation increase was higher in fair-skinned volunteers. The UV dose to minimal pigmentation was higher in darker-skinned persons for single and multiple UV exposures for both UV sources. Going from a single exposure to 6 and 12 exposures, the required dose to minimal pigmentation was reduced by factors of 2 and 3, respectively, for both UV sources, thus reducing the risk of sunburn, but the cumulative dose increased 3- and 4-fold, respectively. This result was independent of skin type and pre-exposure pigmentation. Fading took 4-5 months and was not related to frequency of UV exposure or to ethnic origin.
Ravnbak
Mette H
MH
Department of Dermatology, Bispebjerg Hospital, University of Copenhagen, Denmark. mette@ravnbak.dk
Philipsen
Peter A
PA
Wiegell
Stine R
SR
Wulf
Hans C
HC
D000328:Adult; D004781:Environmental Exposure; D005006:Ethnicity; D005260:Female; D006801:Humans; D007194:India; D008297:Male; D010154:Pakistan; D011829:Radiation Dosage; D012537:Scandinavian and Nordic Countries; D012880:Skin Pigmentation / Q000528:radiation effects*; D013057:Spectrum Analysis; D014466:Ultraviolet Rays