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

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.

Exposure to non-extreme solar UV daylight: spectral characterization, effects on skin and photoprotection.

The link between chronic sun exposure of human skin and harmful clinical consequences such as photo-aging and skin cancers is now indisputable. These effects are mostly due to ultraviolet (UV) rays (UVA, 320-400 nm and UVB, 280-320 nm). The UVA/UVB ratio can vary with latitude, season, hour, meteorology and ozone layer, leading to different exposure conditions. Zenithal sun exposure (for example on a beach around noon under a clear sky) can rapidly induce visible and well-characterized clinical consequences such as sunburn, predominantly induced by UVB. However, a limited part of the global population is exposed daily to such intense irradiance and until recently little attention has been paid to solar exposure that does not induce any short term clinical impact. This paper will review different studies on non-extreme daily UV exposures with: (1) the characterization and the definition of the standard UV daylight and its simulation in the laboratory; (2) description of the biological and clinical effects of such UV exposure in an in vitro reconstructed human skin model and in human skin in vivo, emphasizing the contribution of UVA rays and (3) analysis of photoprotection approaches dedicated to prevent the harmful impact of such UV exposure.

Vitamin C Prevents Ultraviolet-induced Pigmentation in Healthy Volunteers: Bayesian Meta-analysis Results from 31 Randomized Controlled versus Vehicle Clinical Studies.

Background: Repeated nonextreme sun exposures induce skin pigmentation by increasing melanin production and by oxidizing preexisting melanin and melanin precursors. This leads to skin disorders and skin color heterogeneity such as hyperpigmented spots. Objective: We assessed 31 randomized, controlled clinical trials to determine the potential of vitamin C to limit ultraviolet (UV) daylight-induced pigmentation, considering dose response and different skin type populations (Caucasian and Chinese). Materials and Methods: Thirty-one intraindividual, randomized, controlled clinical trials involving Caucasian and Chinese subjects (15-35 healthy male or female volunteers per study, 741 total volunteers) 18 to 50 years of age with Phototype III and individual typology angle (ITA) value between 28 and 49 degrees were analyzed. The 31 studies assessed the potential of vitamin C (formulated with the copolymer Styrène-Anhydride Maléique [SMA]) to decrease pigmentation induced by UV daylight exposure. Results were combined using a Bayesian meta-analysis to provide probabilistic evidence of the effects of vitamin C by dose and population. Results: Vitamin C was effective in reducing pigmentation induced by UV daylight-simulated expositions (4 days at 0.75 Individual Minimal Erythemal Dose [MEDi]) in a dose-dependent manner. During the depigmentation phase, no additive value was provided by the vitamin C, suggesting that the lightening properties described in the literature for vitamin C correspond to an antipigmenting quality rather than a depigmenting effect. Conclusion: Vitamin C is a valuable and safe dermocosmetic antipigmenting compound with a strong effect at 10% possibly useful in preventing signs of photoaging.

In vivo persistent pigment darkening method: a demonstration of the reproducibility of the UVA protection factors results at several testing laboratories.

BACKGROUND/PURPOSE: The aims of the present studies were to check that persistent pigment darkening (PPD) method can produce accurate and reproducible results for high UVA protection factors (UVAPF) and to provide data on the variability between laboratories and on the influence of skin types. METHODS: The Japanese Cosmetic Industry Association (JCIA) PPD method was used to determine the UVAPF in different laboratories of different sunscreen formulations with increasing UVAPF. Two formulations were tested at seven independent laboratories and five products within two laboratories. The influence of skin types on the UVAPF of two products was tested within one laboratory on two panels of volunteers. All laboratories complied with the JCIA method specifications. RESULTS: Reproducible results have been obtained between the different labs and a low and satisfactory variability was achieved with a panel size of 10 subjects. Furthermore, skin type was demonstrated to have no influence within the defined selection criteria. CONCLUSIONS: From this multiple center testing, the PPD method has been shown to be appropriate for testing sunscreen formulations with UVAPFs above 20. It is reasonable to expect that test results will be consistent if an identical protocol is used between laboratories.