Tian Y, Hoshino T, Chen C J, E Y, Yabe S, Liu W
China Medical University, Shenyang, China.
Skin Res Technol. 2009 May;15(2):218-23. doi: 10.1111/j.1600-0846.2009.00358.x.
To establish a pigmentation spot model on human skin and to assess whitening efficacy for whitening products by this established pigmentation spot model.
Twenty subjects between 20 and 45 years old with skin phototype III or IV were selected. Three consecutive daily UV exposures were performed on buttocks of the subjects as follows: Day 1=1 minimal erythema dose (MED), Day 2=0.5 MED and Day 3=0.5 MED. After the first UV exposure, a selected whitening product was applied to the subjects twice a day on UV exposure area. The application of the whitening product to subjects on the exposed areas was continued till Day 27. CM2500d chromameter, Maxmeter MX18 and visual evaluation were used to assess changes of skin color.
A pigmentation spot model after UV exposure was established. The measurement of the pigment spot showed that L* value declined abruptly at Day 3 and then slowly reached to a lowest point at Day 6. L* value of the pigment spot almost remained at the same level until Day 20, thereafter increased slowly. The a* value showed an abrupt increase at Day 3 and slowly reached to a maximal level at Day 6. The a* value slowly declined toward its baseline level. Likewise, the erythema index also increased significantly at Day 3, and reached to a maximal level at Day 6 and then slowly declined. However, L*, a* and erythema indices did not return to their baseline levels during the 27-day period of this study. On the other hand, b* value started to increase from Day 3 and such increase was observed continuously to Day 27. Melanin index also showed a slow increase during the first 3 days. It started to increase rapidly from Day 3 and a to maximal level at Day 9 and maintain at a plateau till Day 27 (with an exception at Day 13). To assess the whitening product by this pigmentation spot model, DeltaL, Deltab*, and DeltaM values were analyzed. It showed that absolute DeltaL value and Deltab*value of whitening products were lower than those values of the vehicle of the whitening product at each checkpoint, while DeltaM value of the whitening product was lower only at Day 9 and Day 20, although no statistically significant differences was found. The visual results also strongly supported that the whitening product enhanced the decrease of pigmentation.
This study showed that repeated UV exposure was able to induce a long extensive period of pigment formation. The resulted pigmentation spot was able to maintain at an elevated level till Day 20. Clinical subjective evaluations together with combined objective instrument measurements were still important to assess whitening and spot-removing ability of a material due to the instrument limitation for color differentiations. This kind of pigmentation spot model can be used to assess whitening efficacy for whitening or spot-removing products. In addition, the combinations of subjective and objective methods were able to serve as advisable references to assess the whitening efficacy of products.
建立人体皮肤色素沉着斑模型，并通过该模型评估美白产品的美白效果。
选取20名年龄在20至45岁之间、皮肤光类型为III或IV型的受试者。对受试者臀部进行连续三天的紫外线照射，具体如下：第1天=1个最小红斑量（MED），第2天=0.5个MED，第3天=0.5个MED。首次紫外线照射后，在紫外线照射区域每天给受试者涂抹选定的美白产品两次。在暴露区域给受试者持续涂抹美白产品直至第27天。使用CM2500d色差仪、Maxmeter MX18和视觉评估来评估皮肤颜色变化。
建立了紫外线照射后的色素沉着斑模型。色素斑的测量结果显示，L值在第3天急剧下降，然后在第6天缓慢降至最低点。色素斑的L值在第20天之前几乎保持在同一水平，此后缓慢上升。a值在第3天急剧上升，在第6天缓慢达到最大值。a值缓慢下降至基线水平。同样，红斑指数在第3天也显著增加，在第6天达到最大值，然后缓慢下降。然而，在本研究的27天期间，L*、a和红斑指数均未恢复到基线水平。另一方面，b值从第3天开始增加，并且这种增加持续观察到第27天。黑色素指数在前3天也呈缓慢上升趋势。从第3天开始迅速上升，在第9天达到最大值，并维持在平台期直至第27天（第13天除外）。为通过该色素沉着斑模型评估美白产品，分析了DeltaL、Deltab和DeltaM值。结果显示，在每个检查点，美白产品的绝对DeltaL值和Deltab值均低于美白产品载体的值，而美白产品的DeltaM值仅在第9天和第20天较低，尽管未发现统计学显著差异。视觉结果也有力地支持了美白产品增强了色素沉着的减少。
本研究表明，重复紫外线照射能够诱导长时间广泛的色素形成。形成的色素沉着斑能够在第20天之前维持在升高水平。由于颜色区分的仪器限制，临床主观评估以及客观仪器测量相结合对于评估材料的美白和祛斑能力仍然很重要。这种色素沉着斑模型可用于评估美白或祛斑产品的美白效果。此外，主观和客观方法的结合能够作为评估产品美白效果的可取参考。
