Revisiting, in vivo, the hair regreasing process by the Sebuprint method.

BACKGROUND: 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). MATERIAL AND METHODS: 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. RESULTS: 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. CONCLUSION: 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.

What is a Caucasian 'fine' hair? Comparing instrumental measurements, self-perceptions and assessments from hair experts.

OBJECTIVE: To determine the various factors contributing to what Caucasian women describe as 'fine hair'. METHODS: Three complementary approaches were used, namely self-evaluation by the volunteer, assessment by a sensorial expert and instrumental measurements, in order to determine some of the possible parameters taken into account by Caucasian women when they describe the notion of fine hair. One hundred fifty one women of Caucasian origin participated in the study. They varied in age, and varied in that some considered themselves as having fine hair, and others not. The instrumental measurements carried out included hair diameter measurements, hair density measurements, hair breakage force, hair flexibility and scalp sebum levels. RESULTS: From six parameters defined initially, four parameters were found to be in common with the three approaches: hair abundance (density), hair thickness, hair resistance and the volume of the hair on the head. The commonly used term 'body' was only common to self and expert evaluation, whereas the influence of curliness was only common to expert evaluation and instrumental measurements. CONCLUSIONS: This study has shown close agreement between sensorial and instrumental findings, and also illustrates how the women participating can subtly and adequately describe their own hair. It is important to note that the words 'fine hair' describes a lot more than just physically thin hair fibres. Ageing is an additional factor that clearly impacts certain parameters associated with 'fine hair' among the volunteers.