Gao J, Liu C, Zhang S, Techer M P, Bouabbache S, Pouradier F, Panhard S
L'Oréal Research & Innovation, Pudong, Shanghai, China.
L'Oréal Research & Innovation, Centre C. Zviak, Saint-Ouen, France.
Skin Res Technol. 2019 Jan;25(1):79-87. doi: 10.1111/srt.12613. Epub 2018 Jul 25.
The regreasing process of hair by sebum is daily observed by consumers. Methods to investigate this phenomenon were scarcely updated since the 1990s, despite the constant progresses in hair cleaning procedures or shampoo formulations. Our objective was first, to develop an in vivo noninvasive method for quantifying the spread of sebum along the hair shaft. Secondly, we use this new method to define the overall kinetics of the hair-regreasing process among two cohorts of Chinese men with opposite self-perceptions of their scalp/hair greasiness (ie, greasy or not greasy).
One hundred and twenty-three Chinese men (aged 18-35 years) participated to the study. The technique used basically adapts the Sebumeter™ technology where supple polymer films are applied onto and along the hair shaft. The sampled hair sebum is further quantified by image analysis/increased transparency.
The technique developed showed an adequate reproducibility under fixed conditions (pressure, investigators, scalp sites, etc.). In the two cohorts of subjects (eg, greasy, nongreasy), hair regreasing process was found sharing a same linear progression with time. The two cohorts of men presented significantly different values in the total amount of spread sebum by an approximately two-fold coefficient, with however comparable average values in the sebum amount present at the root region 48 hours post shampoo. At such timing, the spread of sebum reaches much longer distances in the greasy scalp cohort.
This technique appears promising for assessing the efficacy of cosmetic ingredients (or products) that aim at delaying a natural process that is daily and negatively perceived by consumers.
消费者每天都能观察到皮脂对头发的再润滑过程。自20世纪90年代以来，尽管头发清洁程序或洗发水配方不断进步，但研究这一现象的方法几乎没有更新。我们的目标首先是开发一种体内非侵入性方法，用于量化皮脂沿毛干的扩散情况。其次，我们使用这种新方法来确定两组对头皮/头发油腻程度有相反自我认知（即油腻或不油腻）的中国男性头发再润滑过程的总体动力学。
123名年龄在18 - 35岁的中国男性参与了这项研究。所使用的技术基本采用了皮脂测定仪™技术，即将柔软的聚合物薄膜应用于毛干并沿其放置。通过图像分析/透明度增加对采样的头发皮脂进行进一步量化。
所开发的技术在固定条件（压力、研究人员、头皮部位等）下显示出足够的可重复性。在两组受试者（例如，油腻组、非油腻组）中，发现头发再润滑过程随时间呈现相同的线性进展。两组男性在皮脂扩散总量上的值存在显著差异，系数约为两倍，然而在洗发后48小时根部区域的皮脂量平均值相当。在这个时间点，皮脂在油腻头皮组中的扩散距离长得多。
这项技术对于评估旨在延缓消费者日常负面感知的自然过程的化妆品成分（或产品）的功效似乎很有前景。
