Visible Light and the Skin.

Visible light (VL, 400-700 nm) was previously regarded as nonsignificant with minimal to no photobiologic effects on the skin. Recent studies have demonstrated that in dark-skinned individuals (skin phototypes IV-VI), VL can induce more intense and longer lasting pigmentation compared to ultraviolet A1 (UVA1, 340-400 nm). Additionally, long wavelength UVA1 (370-400 nm) has been shown to potentiate these effects of VL. The combination of VL and UVA1 (VL + UVA1, 370-700 nm) was also able to induce erythema in light-skinned individuals (skin phototypes I-III), which is a novel finding since the erythemogenic spectrum of sunlight has primarily been attributed to ultraviolet B (UVB, 290-320 nm) and short wavelength UVA2 (320-340 nm) only. Although biologic effects of VL + UVA1 have been established, there are no guidelines in any country to test for photoprotection against this waveband. This invited perspective aims to present the evolution of knowledge of photobiologic effects of VL, associated phototesting methodologies, and current position on VL photoprotection.