The synergistic effect of minimal amounts of long-wavelength ultraviolet A1 and visible light on pigmentation

Document Type

Conference Proceeding

Publication Date


Publication Title

Journal of Investigative Deramtology


Visible light has been shown to induce dark and persistent pigmentation in addition to erythema, thermal damage, and free radical production. The pigmentation phases include immediate pigment darkening (IPD), persistent pigment darkening (PPD), and delayed tanning (DT) that occur immediately, between 2-24 hours, and 3-5 days after irradiation respectively. Variations in spectral outputs of light sources can lead to differences in visible light induced pigmentation responses. The study aimed at investigating the synergistic effect of minimal amounts of long-wavelength ultraviolet A1 (UVA1) radiation and visible light on pigmentation and erythema response. Subjects with Fitzpatrick skin phototype IV-VI were recruited. On day 0, subjects were irradiated on either side of their back with a dose of visible light using two different light sources; one containing pure visible light while the other containing visible light with trace amounts of long wavelength UVA1. Evaluations were performed immediately (to assess IPD), 24 hours (to assess PPD), 7 days (to assess DT), and 14 days (to assess DT) after irradiation. Assessment methods included investigator's global assessment (IGA), clinical photography, and spectroscopy. IPD, PPD and DT responses were observed with both light sources. However, the intensity of the pigmentation was approximately two times greater when subjects were irradiated with the light source containing trace amounts of UVA1 along with visible light compared to that with pure visible light alone. In conclusion, pure visible light induces pigmentation. The degree of this pigmentation is significantly enhanced by the presence of trace amount of UVA1 light. This suggests the necessity for development of sunscreens and other mechanisms to provide photo-protection against this part of the solar spectrum.




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