New method for evaluation of Asian skin radiance

For instance, providing supporting data on claimed benefits is mandatory in the countries of the European Union. Similar requirements have been implemented in South-East Asia countries in 2008 according to the Asean Cosmetic Directive. In most cases (e.g. moisturising, whitening, anti-wrinkles, etc.), this demonstration is easy to achieve thanks to the existence of numerous validated instrumental methods suitable for the measurement of the corresponding skin properties.1 However, some claims put forward by the cosmetic manufacturers constitute strong challenges regarding their assessment. Among them, evaluating the in vivo efficacy of products designed to improve the radiance of the complexion or to recapture a healthy appearance was particularly difficult to handle since several physiological factors are clearly involved. Actually, even psychological factors are probably involved (joy, happiness, wellbeing, relaxation). Another source of difficulty lies in the lack of universal definition of skin radiance. A first solution to this problem was provided a few years ago by some members of our team2 who have developed a visual evaluation of the radiance of the complexion. A second different approach which included a self-assessment questionnaire, expert assessment and image processing of facial photographs has been proposed two years later.3 In this work, statistical analysis was used to lead to multiple regression equations where the skin radiance is determined by a linear formula combining different factors. This article will present the approach that we have used to develop a method suitable for the evaluation of the in vivo efficacy of cosmetic treatments aimed at improving the radiance of the facial skin.

Defining a common language

Because of the absence of one universal definition of complexion’s radiance, brainstorming sessions with beauticians, dermatologists and women (representing consumers of cosmetics) were organised in order to define the characteristics of a radiant complexion and the factors contributing to the radiance by arriving at a consensus. Thus, there have been identified several parameters or descriptors involved in the perception of skin radiance. These descriptors were the Colour (C), the Luminosity (L), the Brightness (B) and the Transparency (T) of the skin. Although there are several instrumental methods to measure the colour of the skin (the chromametry being the most commonly used), the other facets of this complex claim were out of reach of instrumental measurements. Therefore the original idea was to replace the lacking instrumentation by a sensory assessment by carefully trained experts. Actually it appeared desirable also to have a visual evaluation that could be representative of the expectations held by consumers. Based on the visual evaluation and scoring of a set of several descriptors of the skin’s radiance by trained assessors, this original method was called CLBT, an acronym for colour, luminosity, brightness and transparency. Over two years, this sensory evaluation of the radiance of skin’s complexion has been largely and successfully used to evaluate the capabilities of cosmetic products to enhance the radiance of the skin. However one limitation of the method was that it was restricted to the assessment of Caucasian skin only since its validation was done in France using Caucasian women.2 Therefore we have recently modified the initial method in order to obtain a method suited to the investigation of the skin of Asian subjects. Round the table meetings and visual observations of many Asian female subjects have led to some modifications of the initial Caucasian CLBT method. Thus luminosity, brightness and transparency descriptors were kept since they were considered as pertinent and adapted to the evaluation of both Caucasian and Asian subjects. But the hues selected for the Asian version of the method were brown, light brown, beige, olive, yellow and light pink (compared to beige, olive, red pink and light pink for the Caucasian method).