Key points are not available for this paper at this time.
Abstract Human skin is exposed to visible light ( VL ; 400–700 nm) and long‐wavelength ultraviolet A1 ( UVA 1) 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% UVA 1 ( VL + UVA 1) 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 + UVA 1 and pure VL 24 h after irradiation. Clinical and spectroscopic assessments demonstrated a robust response at VL + UVA 1 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 + UVA 1 resulting in biologic responses were calculated. Results indicate that approximately 2 h of sun exposure, which equates to VL + UVA 1 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.
Kohli et al. (Thu,) studied this question.