Both long-wavelength ultraviolet A (UVA1) and visible light can induce pigmentation in people with Fitzpatrick skin types IV–VI, according to results of research published in theJournal of Investigative Dermatology.
This study suggests that visible light plays a significant role in skin pigmentation, said Dr. Heather Woolery-Lloyd, who highlighted this study during a presentation at the second annual Skin Spectrum Summit in Montreal on May 13, 2017.
Dr. Woolery-Lloyd is the director of Ethnic Skin Care, and voluntary assistant professor at the Department of Dermatology and Cutaneous Surgery, University of Miami Miller School of Medicine in Miami.
During the investigation, two electromagnetic radiation sources were used to irradiate the lower back of 20 volunteers with Fitzpatrick skin types IV-VI: UVA1 (340 to 400 nm) and visible light (400 to 700 nm). Pigmentation was assessed by visual examination, digital photography with a cross-polarized filter, and diffused reflectance spectroscopy at seven-time points over a two-week period.
The findings revealed that pigmentation induced by visible light was darker and more sustained, noted Dr. Woolery-Lloyd.
“UVA1 and visible light doses used in this study are easily obtained from daily sun exposure,” she said.
For example, Dr. Woolery-Lloyd explained that the fluence rate of the solar spectrum of visible light, during clear sky conditions at sea level, is about 15 times higher than that of UVA. “A dose of 20 J/cm2 of UVA (1-hour daylight) would correspond to about 300 J/cm2 of visible light,” she said.
“The findings from this study are important because all of us have patients who say ‘I went to the beach and wore SPF 100, and I reapplied it every two hours, and my skin got tanned.’ You might be wondering why this happens,” said Dr. Woolery-Lloyd.
Dr. Woolery-Lloyd said “The reason why we think that [pigmentation occurs despite use of sunscreen] is because visible light also induces hyperpigmentation and our traditional sunscreens that protect against UVA and UVB provide no protection against visible light,” she said.
More information about the Skin Spectrum Summit can be found at www.skinspectrum.ca. Registration is still open for the Vancouver Skin Spectrum on May 27.