A precise analysis of the relative contribution of UVA1 and visible light colour domains in solar light‐induced skin pigmentation

Abstract

Background Solar light induces or aggravates hyperpigmentation issues. The contribution of UVA1, as well as visible light (VL), especially high‐energy blue‐violet visible (HEV) light, is now clearly established. Objectives This work aimed at determining the relative contribution of UVA1, HEV and VL wavelength bands and their sub‐domains in pigmentation induction. Methods Two clinical studies using solar simulators equipped with specific bandpass physical filters were carried out. Volunteers (FSPT III‐IV) were exposed on the back to UVA1 + HEV (350–450 nm), UVA1 (350–400 nm), HEV (400–450 nm) or part of UVA1 + HEV (370–450 nm) in Study 1 (n = 27) and to VL (400–700 nm), HEV (400–450 nm), Blue (400–500 nm), Green (500–600 nm) and Green+Red (500–700 nm) domains in Study 2 (n = 25). Pigmentation level was assessed by visual scoring and colorimetry at different time points postexposure, up to Day 43. Results Induced pigmentation was detected in all exposed conditions, peaking at 2 h and thereafter progressively decreasing but remaining persistent up to Day 43. In Study 1, UVA1 showed an additive effect with HEV, with a significant contribution coming from the Longest UVA1 rays (370–400 nm). Study 2 demonstrated that 24 h postexposure, the Blue domain accounted for 71% of VL‐induced pigmentation, the HEV one for 47%, the Green one for 37% and the Green+Red one for 36%, confirming no significant effect for Red light. Conclusions Altogether, these results underline the need for UVA1 photoprotection up to 400 nm and highlight the importance of protecting the skin from solar VL wavelengths and especially from HEV, Blue and Green light, to limit induced pigmentation.

2‐Mercaptonicotinoyl glycine prevents UV‐induced skin darkening and delayed tanning in healthy subjects: A randomized controlled clinical study

“…Although the simulated UVDL spectrum used in this study covers part of the visible light (VL) spectrum up to 450 nm, including blue light which is known to be important for VL‐induced pigmentation, 24 we were not able to determine the impact of our product on exposure to VL. This is a limitation of our study arising from our proof‐of‐concept design performed with controlled UV exposure under solar simulator conditions.…”

International Consensus on Anti-Aging Dermocosmetics and Skin Care for Clinical Practice Using the RAND/UCLA Appropriateness Method

“…10 Similarly, high-energy VL protection with tinted sunscreens containing iron oxides and/or pigmentary titanium dioxide is especially important for dark-skinned individuals as they are more sensitive to VL-induced pigmentary disorders. [11][12][13] Sunscreen technology differs by country with fewer sunscreen options in the US. 12 Generally, photoprotection is not always well adapted to darker phototypes as there is a large variation in constitutive skin tones between FST IV to VI, making it more difficult to find a good color match for tinted/ iron oxide sunscreens to protect against VL.…”

“…As an alternative for individuals (for example men) who find pigmented products cosmetically unacceptable, newer organic filters may offer some protection in the near visible region, 14 but tinted products containing pigments are still required to provide high protection against high energy VL to prevent pigmentary disorders. 13 Furthermore, although makeup has been found to offer no photoprotection, 15 a broad-spectrum sunscreen camouflage foundation containing a high concentration of iron oxides may offer high-energy VL protection. 16 For melasma, sunscreens should be broad-spectrum with high SPF, and provide high protection against UVA and VL.…”

Awareness of sun exposure risks and photoprotection for preventing pigmentary disorders in Asian populations: Survey results from three Asian countries and expert panel recommendations

“…Although some organic filters have been reported to provide protection in the near visible region, 56–58 the use of tinted products containing pigments is required to provide high protection against HEV to prevent pigmentary disorders 59 . Protection with inorganic tinted sunscreens containing pigmentary titanium dioxide and/or iron oxides including red iron oxide (Fe 2 O 3 ), yellow iron oxide (Fe(OH) 3 /FeOOH), and black iron oxide (Fe 3 O 4 ) effectively block VL (specifically HEV) 60 .…”

“…55 Although some organic filters have been reported to provide protection in the near visible region, [56][57][58] the use of tinted products containing pigments is required to provide high protection against HEV to prevent pigmentary disorders. 59 Protection with inorganic tinted sunscreens containing pigmentary titanium dioxide and/ or iron oxides including red iron oxide (Fe 2 O 3 ), yellow iron oxide (Fe(OH) 3 /FeOOH), and black iron oxide (Fe 3 O 4 ) effectively block VL (specifically HEV). 60 Tinted sunscreens, to protect against HEVL and UVA1-induced hyperpigmentation, may help cover pigmentary disorders if cosmetically acceptable and available in a range of colors tailored to the patient's constitutive skin tone.…”