BACKGROUND: The dynamics of ultraviolet (UV)-induced melanogenesis have been well characterized for single UV exposures. However, our knowledge of the effects of repeated UV exposures on the development of new pigmentation is limited. OBJECTIVES: To characterize the dynamics and dose dependence of pigmentation induction by repeated UV exposures using two different UV sources. METHODS: A total of 40 healthy subjects participated in the study: 21 were exposed to a 5% UVB/95% UVA source and 19 were exposed to a 2% UVB/98% UVA source. Skin phototypes 2-3 were represented. Subjects were exposed one to three times per week. The minimal erythemal dose and minimal melanogenic dose of all subjects were determined, and both visual and instrumental observations of the development of pigmentation and erythema were recorded. RESULTS: Dark-brown pigmentation could be produced by a cumulative UV dose of 4200 J m(-2) given as 10 exposures over 5 weeks. However, comparable pigmentation could also be induced by a cumulative dose of 2900 J m(-2) given as eight exposures over 4 weeks. The lowest cumulative dose of 1900 J m(-2) given over 4 weeks produced moderate pigmentation. The 2% UVB source led to earlier and darker pigmentation than the 5% UVB source did for equally erythemogenic doses. CONCLUSIONS: These observations show that the dynamics of melanogenesis induced by repeated exposures depends on UV dose, dose interval and emission spectrum. They also indicate that increasing the UV dose above a certain level of cumulative exposure does not significantly increase the level of UV-induced pigmentation.
BACKGROUND: The dynamics of ultraviolet (UV)-induced melanogenesis have been well characterized for single UV exposures. However, our knowledge of the effects of repeated UV exposures on the development of new pigmentation is limited. OBJECTIVES: To characterize the dynamics and dose dependence of pigmentation induction by repeated UV exposures using two different UV sources. METHODS: A total of 40 healthy subjects participated in the study: 21 were exposed to a 5% UVB/95% UVA source and 19 were exposed to a 2% UVB/98% UVA source. Skin phototypes 2-3 were represented. Subjects were exposed one to three times per week. The minimal erythemal dose and minimal melanogenic dose of all subjects were determined, and both visual and instrumental observations of the development of pigmentation and erythema were recorded. RESULTS: Dark-brown pigmentation could be produced by a cumulative UV dose of 4200 J m(-2) given as 10 exposures over 5 weeks. However, comparable pigmentation could also be induced by a cumulative dose of 2900 J m(-2) given as eight exposures over 4 weeks. The lowest cumulative dose of 1900 J m(-2) given over 4 weeks produced moderate pigmentation. The 2% UVB source led to earlier and darker pigmentation than the 5% UVB source did for equally erythemogenic doses. CONCLUSIONS: These observations show that the dynamics of melanogenesis induced by repeated exposures depends on UV dose, dose interval and emission spectrum. They also indicate that increasing the UV dose above a certain level of cumulative exposure does not significantly increase the level of UV-induced pigmentation.
Authors: Sharon A Miller; Sergio G Coelho; Barbara Z Zmudzka; Janusz Z Beer Journal: Photodermatol Photoimmunol Photomed Date: 2006-04 Impact factor: 3.135
Authors: Yuji Yamaguchi; Sergio G Coelho; Barbara Z Zmudzka; Kaoruko Takahashi; Janusz Z Beer; Vincent J Hearing; Sharon A Miller Journal: Exp Dermatol Date: 2008-03-23 Impact factor: 3.960
Authors: Leticia U Colmenares; Sergio Coelho; Sharon A Miller; K B Boomer; Janusz Z Beer Journal: Photodermatol Photoimmunol Photomed Date: 2013-06 Impact factor: 3.135
Authors: Sharon A Miller; Sergio G Coelho; Scott W Miller; Yuji Yamaguchi; Vincent J Hearing; Janusz Z Beer Journal: Photodermatol Photoimmunol Photomed Date: 2012-08 Impact factor: 3.135
Authors: Sergio G Coelho; Barbara Z Zmudzka; Lanlan Yin; Sharon A Miller; Yuji Yamaguchi; Taketsugu Tadokoro; Vincent J Hearing; Janusz Z Beer Journal: Exp Dermatol Date: 2013-04 Impact factor: 3.960
Authors: Michaela Brenner; Sergio G Coelho; Janusz Z Beer; Sharon A Miller; Rainer Wolber; Christoph Smuda; Vincent J Hearing Journal: J Invest Dermatol Date: 2008-10-23 Impact factor: 8.551
Authors: Sergio G Coelho; Wonseon Choi; Michaela Brenner; Yoshinori Miyamura; Yuji Yamaguchi; Rainer Wolber; Christoph Smuda; Jan Batzer; Ludger Kolbe; Shosuke Ito; Kazumasa Wakamatsu; Barbara Z Zmudzka; Janusz Z Beer; Sharon A Miller; Vincent J Hearing Journal: J Investig Dermatol Symp Proc Date: 2009-08