Long‐wavelength Ultraviolet A1 and Visible Light Photoprotection: A Multimodality Assessment of Dose and Response

• Published in: Photochemistry and photobiology Vol. 96; no. 1; pp. 208 - 214
• Main Authors: Kohli, Indermeet, Braunberger, Taylor L., Nahhas, Amanda F., Mirza, Fatima N., Mokhtari, Mohsen, Lyons, Alexis B., Kollias, Nikiforos, Ruvolo, Eduardo, Lim, Henry W., Hamzavi, Iltefat H.
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.01.2020
• Subjects: Adult; Assessments; Biological effects; Dose-Response Relationship, Radiation; Erythema; Female; Histology; Human behavior; Humans; Irradiation; Light; Light effects; Light sources; Male; Middle Aged; Skin; Skin - radiation effects; Spectroscopic analysis; Spectrum Analysis - methods; Statistical analysis; Sun screens; Sunscreening Agents; Sunscreens; Tanning; Ultraviolet radiation; Ultraviolet Rays; Wavelength; Wavelengths
• ISSN: 0031-8655; 1751-1097; 1751-1097
• DOI: 10.1111/php.13157

Human skin is exposed to visible light (VL; 400–700 nm) and long‐wavelength ultraviolet A1 (UVA1) radiation (370–400 nm) after the application of organic broad‐spectrum sunscreens. The biologic effects of these wavelengths have been demonstrated; however, a dose–response has not been investigated. Ten subjects with Fitzpatrick skin phototype IV‐VI were enrolled. Subjects were irradiated with 2 light sources (80–480 J cm−2): one comprising VL with less than 0.5% UVA1 (VL+UVA1) and the other pure VL. Skin responses were evaluated for 2 weeks using clinical and spectroscopic assessments. 4‐mm punch biopsies were obtained from nonirradiated skin and sites irradiated with 480 J cm−2 of VL+UVA1 and pure VL 24 h after irradiation. Clinical and spectroscopic assessments demonstrated a robust response at VL+UVA1 sites compared with pure VL. Histology findings demonstrated a statistically significant increase in the marker of inflammation (P < 0.05) and proliferation (P < 0.05) at the irradiated sites compared with nonirradiated control. Threshold doses of VL+UVA1 resulting in biologic responses were calculated. Results indicate that approximately 2 h of sun exposure, which equates to VL+UVA1 dose (~400 J cm−2), is capable of inducing inflammation, immediate erythema and delayed tanning. These findings reinforce the need of photoprotection beyond the UV range. Human skin is exposed to visible light (VL; 400–700 nm) and long‐wavelength ultraviolet A1 (UVA1) radiation (370–400 nm) after the application of organic broad‐spectrum sunscreens. The biologic effects of these wavelengths have been demonstrated; however, a dose–response has not been investigated. Threshold doses of VL+UVA1 (370–700 nm) resulting in biologic responses were calculated. Results indicate that approximately 2 h of sun exposure, which equates to an approximate VL+UVA1 dose of 400 J cm−2, is capable of inducing inflammation, immediate erythema and delayed tanning. These findings reinforce the need of photoprotection beyond the UV range.