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Keywords:

  • clinical evaluation;
  • facial skin tone;
  • instrumental evaluation/physical measurements;
  • pigmentation

Synopsis

  1. Top of page
  2. SynopsisRésumé
  3. Introduction
  4. Material and methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References

The pigmentation patterns of facial skin of 354 healthy Chinese women aged 18–80 years were investigated clinically and instrumentally. Chromasphere® was used to acquire pictures from the cheeks of subjects. Facial skin tone was described by L* parameter from the L,a,b system as well as Individual Typology Angle (ITA). Results show that skin tone becomes significantly darker along the life span. Both size of hyper-pigmented spots and their contrast with surrounding skin were found increased with age. As additional study, 40 women from these 354 subjects were asked to apply daily a whitening cosmetic product for a 2-month period. Such application led to a significantly lighter skin tone, although this study was not vehicle controlled and we cannot exclude that the increase in L* observed was in some part because of cumulative effects of previously used whitening products, there was an association with lighter skin tone as assessed through both instrumental measurements and self-perception by most subjects.

Résumé

Les profils pigmentaires du visage de 354 femmes chinoises âgées de 18 à 80 ans ont étéétudiés d’un point de vue clinique et de façon expérimentale. La Chromasphere® a été utilisée pour obtenir des photos des joues des sujets. La teinte de la peau était déterminée par le paramétre L* du systéme L, a, b ainsi qu’avec l’angle individuel typologique (I.T.A.). Les résultats montrent que la couleur de la peau s’assombrit au cours de la vie. La taille des taches hyper pigmentées ainsi que le contraste avec la peau environnante augmentent avec l’âge. Dans une étude complémentaire, il a été demandéà 40 de ces femmes d’appliquer chaque jour un produit cosmétique éclaircissant durant 2 mois. Une telle application conduit à un éclaircissement significatif de la couleur de la peau. Cette étude n’ayant pas de témoin véhicule, on ne peut exclure que l’augmentation observée du paramétre L* est la conséquence, pour une part, d’un effet cumulatif des produits blanchissants précédemment utilisés. Il y avait une convergence sur la teinte de peau plus claire évaluée par des mesures instrumentales et par la perception de la plupart des sujets.


Introduction

  1. Top of page
  2. SynopsisRésumé
  3. Introduction
  4. Material and methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References

The colour of the skin, and it’s numerous associated wordings (tone, complexion, fair, dark, hue, glow, etc), is a widely documented topic whose scope goes beyond of Dermatology or Cosmetology. It has many ethnic, social, biological and medical features [1].

Genetically driven, the colour of human skin results from many cellular and biochemical actors, among which melanins, melanocyte activity, melanosome shapes or distribution, tyrosinase and other subsequent melanocyte enzymes [2–4]are probably the most important driving factors, although not exhaustive. Epidermal turnover, presence of other pigments such as carotenoids, volume of the underlying blood vessel network are evident additional factors [5, 6] that confer skin an ‘overall’ colour, which is instinctively perceived by laymen, primarily, as fair or dark. Through an immediate visual assessment, the human eyes and brain quickly integrate various features of the human face.

Although the fairness or darkness of the skin has ethnological implications, they may entail many ambiguities, too. A dark, or ‘black’ skin, is not an African specific trait. Pakistanese, Indian, Melanesian populations (from the Greek melas, black), etc., share this phenotype.

With regard to skin complexion and attitude towards sun exposure, Asia, particularly China, shows three cultural features, distinct from Western standards or habits. On a first hand, fairness or darkness of the skin has a clear social facet. Since the early ages of China, a fair skin is associated with upper social class, i.e., protected from sun, living in cosy houses, the opposite of farmers or outside (hard) workers. This is likely a strong driving factor in the -specifically Asian- demand for whitening cosmetic products. On a second hand, secular traditions have associated sun exposures with skin darkening and its anaesthetical consequences (spots, lentigines, freckles, etc). This accounts, in China for example, for the popular wear of sun protective components (umbrellas, masks, UV shields, etc) on sunny days. Lastly, with regard to ageing, traditional and popular Chinese sayings often associate age and changes in skin tone: inline image: ‘married or old women turn yellow’

Altogether, these three cultural elements led us to attempt to reach two complementary objectives: (i) to confirm, clinically and instrumentally, the changes in skin complexion of Chinese women of various ages as previously published [7] and (ii) to determine the extent of possible changes in facial skin complexion brought by a whitening product, following a 2-month regular use.

Material and methods

  1. Top of page
  2. SynopsisRésumé
  3. Introduction
  4. Material and methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References

Subjects cohorts

  • 1
     Study on ageing (January 2007).The study included 354 healthy Chinese women, aged 18–80, residing in Shanghai since more than 10 years. They were recruited through agency, informed about the conditions of the study and further signed an informed consent. Apart from the absence of both skin disease and any medication intake, no particular exclusion criteria were used. The selection of subjects aimed at balancing the sizes of all age classes, from 18 to 80 years.
  • 2
     Study on a whitening product (January to March 2010). Forty-three healthy women, aged 25–60 years, free from skin disease, medication and non-pregnant were included in the study. These women were chosen from our databases, built from previous studies (38 from the study on ageing in 2007 were enrolled) and further signed an informed consent. They were selected according to previously recorded skin features (skin tone from average to dark, number of pigmented spots equal or higher than grade 2 of Atlas grading Fig. 1). From January to March, they were asked to apply daily (morning, all face) a whitening product (L’OREAL Revitalift White SPF18 PA+++) that was supplied in a blind jar instead of their usual whitening product that they discontinued 2 weeks prior to the study. They were then seen for instrumental imaging at two visits, T0 (January 2010), prior to starting product application, and T2month (March 2010), end of application. All instrumental recordings were carried out on bare skin (no application of any cosmetic product 1 day prior to the examination). At T2month, subjects had to fill an individual questionnaire for collecting their own perception on product efficacy.
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Figure 1.  Photographic standards of spots density grading, from the Skin Atlas.

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Clinical assessments

The same reference grading scale was used, i.e., the Skin Aging Atlas, Asian Type’, as previously published [8]. The latter gathers clinical grading of various facial signs. It is used by our trained technicians for many purposes, in this study, helping to assess both the skin tone and the severity of pigmentation on cheeks. Accordingly, skin tones and pigmentation of all subjects were evaluated by same expert of our group and then scored through the Atlas grading system.

Instrumental recordings

They were carried out on the cheeks of volunteers through the use of the Chromasphere® (Chromosphere, Paris, France) [9] which is a diffuse daylight lightning device coupled to a spectro radiometer and/or calibrated 3CCD digital cameras. It allows multi-scale colour measurements on a software-selected area of the cheek (a square of 400 pixels by 400pixels with 1/7mm for one pixel). Chromasphere®, coupled to a Skin Color Chart® [10], was used to measure the facial skin tone by L*a*b* parameters and derived Individual Typology Angle (ITA) parameter [11], according to the following formula:

ITA = [ArcTan (L*-50)/b*)] × 180. The higher ITA, the lighter the skin.

Instrumentally, facial pigmentation was determined on the cheek bone area by image analysis based on colour system from three criteria, namely (i) the total surface of pigmentation spots covering on cheek, (ii) their darkness(L*) of pigmentation spots and (iii) the average size of these spots, (expressed in mm²).

Statistics

SPSS 16 was used in the statistical calculation. Data are given were by mean ± SD respectively unless otherwise indicated. Statistical analysis was performed using linear correlation coefficient for age effect and paired sample student t test for product efficacy. All tests were two-sided taking P < 0.05 as the significance level and performed using SPSS.

Results

  1. Top of page
  2. SynopsisRésumé
  3. Introduction
  4. Material and methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References

Effect of age on skin tone and pigmentation

Figure 2a illustrates the statistically significant ‘regular’ (trend line) decrease in skin lightness with age, logically confirmed by comparable progressive changes in ITA (Fig. 2b). Clinical grading shows, too, a regular increase in skin darkness, although with wider inter-individual variations, witnessed by a smaller ‘r’ (Fig. 3). Both instrumental and clinical scores were found highly correlated (r = 0, 67, P < 0,001) as shown in Fig. 4. With regard to a and b parameters, both show tendency to increase with age, witnessed by a slight positive slope and with significant change on a parameter with age and albeit non-significant on b parameter (Fig. 2c, d). As for pigmented spots, ‘viewed’ by Chromasphere®, it appears clear that the total surface of facial spots statistically increase with age, as illustrated by Fig. 5. This global trend likely integrates two parameters: a statistical increase in the average spots area (Fig. 6) with age, as well as progressive darkening -or lightness decrease of spots- as expressed in Fig. 7.

image

Figure 2.  (a) Changes in skin lightness (L*) of skin tone with age. (b) Changes in skin I.T.A value with age. (c) Changes in skin redness (a*) of skin tone with age. (d) Changes in skin yellowness (b*) of skin tone with age.

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Figure 3.  Changes in skin lightness with age, from clinical/colour chart evaluation.

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Figure 4.  Skin lightness correlation between objective (L*) and clinical assessments.

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Figure 5.  Changes in total spots surface (cheeks) with age.

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Figure 6.  Changes in average spot areas (cheeks) with age.

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Figure 7.  Changes in L* of spots with age. A regular darkening.

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Clinically speaking, the scorings from the Atlas scale confirmed these two major trends, i.e., a ‘regular’ increase in both severity (Fig. 8) and density of spots (Figs 1 and 9). Again, both instrumental and clinical data were all found highly correlated, as shown for illustrative purpose in Fig. 10. All these data converge towards an increase in contrast between facial spots and their surrounding environment with age, leading to a more obvious spotty appearance at a glance.

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Figure 8.  Changes in average pigmentation severity (Atlas grades) with age.

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Figure 9.  Changes in the density of spots with age (grading from the Skin Atlas).

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Figure 10.  Correlation between measurements of total and clinical grading of skin pigmentation, from the Skin Atlas.

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Effect of a whitening product

As indicated in Table I, the application of the whitening product for a 2 months led to a statistical increase in skin lightness/tone on cheeks, as expressed by changes in L* and ITA between T0 and T2month (increased in average by about 2 and 3 units, respectively). As for pigmented spots (Table II), a not significant (P = 0.096) trend towards a decrease in their average area was observed. However, their darkness showed a statistical decrease, associated with an increase in the surrounding skin lightness, i.e., a less contrasted facial heterogeneity.

Table I.   Changes in skin tone after application of a whitening product
 T0T2monthT2month–T0T2month vs. T0
L*63.67 ± 1.9965.66 ± 1.84+1.99 ± 1.85P < 0.001
Individual typology angle30.67 ± 4.1733.31 ± 3.57+2.65 ± 2.34P < 0.001
Table II.   Changes in spot average area and their intrinsic L*, after application of a whitening product
 T0T2monthT2month–T0T2month vs. T0
Area (mm2)2.96 ± 1.212.69 ± 0.91−0.27 ± 1.04P = 0.096
L* sp59.94 ± 2.4561.9 ± 2.35+1.95 ± 2.31P < 0.0001

Answers to the questionnaire (see Table III), at least with regard to ‘a brighter skin’, ‘a less dull’, ‘fairer skin’ or ‘less dark spots’ appear in good agreement with instrumental measurements.

Table III.   Summary of answers to questionnaire by volunteers
QuestionsAgree+ (%)Somewhat agree (%)
Your complexion looks brighter/more luminous44.237.2
Your complexion looks less dull44.241.9
Your complexion looks more transparent34.934.9
Your skin colour looks more even toned32.637.2
Your skin looks clearer30.246.5
Your skin looks fairer46.537.2
The colour of dark spots looks reduced37.239.5
The number of dark spots looks reduced32.637.2
The size of dark spots looks reduced23.346.5
Your skin feels healthier39.546.5

Discussion

  1. Top of page
  2. SynopsisRésumé
  3. Introduction
  4. Material and methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References

The present study clearly confirms the results from De Rigal et al. [12] and Liu et al. [7], although the latter team did not use comparable instruments, same skin sites and protocol in 4 different locations in China (Shanghai included). Similar to De Rigal study, we observed that age progressively darkens the skin of Shanghaiese women, at a similar (slow) rate as that found by Liu et al. Despitedifferent instrumental approach, subjects, and locations, both studies depict a comparable statistical decrease in ITA, at a rate of about one unit in a 4-year period, seemingly a rather slow darkening process. The same holds true for global Lightness (L*) which, in our study, shows a statistical decrease by one L* unit in about a 10-year time period. This value has to be compared to an average decrease in L* by about 2 units from a non-tanned to tan skin in Caucasian’s, according to previous findings [9]. It has to be reminded that the definition domain of L* ranges 0 (black) to 100 (white). With regard to human subgroups, skin lightness then shows a rather small dynamic range as, from the darkest to the fairest skins, L* values, on cheek bones, range by approximately 20 units (45–65, respectively), Asian skin appearing intermediate [12]. With regard to a and b parameters, our study found a trend in increase of both with age, in a rather acceptable agreement with data from de Rigal and colleagues. Such finding could be summarized by a slight and progressive skin ‘yellowing’, illustrating somewhere the old Chinese diction quoted. The slow skin darkening observed here likely results from various factors, among which sun exposure has a consequent ‘weight’, known as photo-ageing that slowly and cumulatively imprints on exposed skin [13–16]. In their work, Liu et al. did not observe much change in ITA on unexposed skin site (buttocks). On sun-exposed site, such as face, sun-induced pigmentation is likely coupled to an age-induced slowing down of epidermal renewal [17, 18] with age, leading to an epidermis more prone to longer retain pigmented keratinocytes and corneocytes. As for melanocytes population, their epidermal density has been shown declining with age [19, 20], suggesting a long-term ‘lightening’ of the skin, i.e., an apparent paradox with our data from this study. However, most of the related studies were carried out on Caucasian skin albeit the melanocytes density was shown increased in naevis. It cannot be excluded, however, that the remaining epidermal melanocytes exhibit enhanced melanin synthesis. Furthermore, a deep invasion of melanocytes in dermis, or at least superficial dermis, a tissue of a slower turn over than epidermis, might explain a rather long persistency and/or stimulation of pigmentation, as suggested by a Japanese histological study depicting such dermal melanosis [21]. Results from the study of Liu and colleagues failed to demonstrate, on unexposed skin sites, an increased lightness with age that could have possibly resulted from a decrease in epidermal melanocytes. Whatsoever, the frequency and severity of pigmented facial spots clearly confer to Asian subjects a rather specific trait, rarely seen in Caucasian’s. This suggests that skin pigmentation mechanisms or pathways may differ in both human groups.

Interestingly, instrumental data and clinical scorings appear well correlated, although the latter show some wider inter-individual variations, likely due to the discontinuous criteria of the scoring scale. Even to, our results confirm that clinical assessments through standardized photographs bring strong validity.

Applying a whitening (or lightening) cosmetic product for a 2-month period leads to an increase in L* by about 2 units, as expressed by paired comparisons (T2 vs. T0), irrespective with the rather large inter-individual pigmentation levels (min 60,8 max 68,2 at T0). Such range is in good agreement with the one found in De Rigal study. However, application of the product, as seen by paired comparisons, led to an average increase of about 2 L* units and 3 for I.T.A. Average percentage of improvement efficacy (see Fig. 11). This result was perceived by a majority of subjects, as declared in the questionnaire. Such level of increase is probably slightly underestimated. In a previous paper [22], we observed a decrease in L* in all subjects (Shanghaiese women) from January to August, a decrease we interpreted as a result of sun exposures. The latter, although non-desired for cultural reasons, are hardly avoidable in the routine of daily life. In our experimental conditions, we assumed that intensities of UVB and UVA rays logically increased from January to March, although objective data are missing. Whatsoever, an increase by about 2 L* units brought by the cosmetic product appears high, and a mendacious approach would quickly conclude that the product has counterbalanced about 20 years of age-induced colour changes. Nothing would probably be more distorting the reality. As a matter of fact, the lightening effect brought by the product likely arises from dual factors, i.e., the active ingredient used, of a well-proven action (vitamin B3, [23] and confirmed here, albeit of a modest effect on spot areas, and the protective effect of an efficient sunscreen in the UVB and UVA range, the first one aiming at correcting, the second one at preventing. However, as this applied study was not vehicle controlled, the respective (intrinsic) efficacy of actives, among the formula, can hardly be estimated. In addition, we cannot exclude that the increase in L* observed here results, too, in a cumulative effect with the whitening previous product used by the subjects they were asked to stop 2 weeks prior the study. In fact, a cosmetic whitening effect (apart from ‘instant whitening’ related to immediate camouflage by external pigments) requires rather long-term and repeated applications.

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Figure 11.  Clinical picture of whitening efficacy after two months treatment.

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We believe that the progressive changes in the skin tone over a life span that we observed in the first study are integrating the effects of all cumulative exposures to sun. In some extent, they can be regarded as a kind of ‘sun scars’, which an efficient short-term, provisory (as long as continuously applied) aesthetic solution can be afforded against through safe and efficient whitening products. However, it is very likely that a regular skin protection from sun, afforded by efficient sunscreening products, at early ages, would greatly decrease photo-damages on skin, induced pigmentation included. With such regular skin prevention, the statistical slope of colour changes in skin colour we have observed here, along the life span, would then probably be of a smaller angle, traducing a slower progressive darkening of the skin, from early to advanced ages.

Acknowledgements

  1. Top of page
  2. SynopsisRésumé
  3. Introduction
  4. Material and methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References

The authors deeply thank all those who contributed in this study and particularly Saint-Leger Didier for his help to achieve this paper.

References

  1. Top of page
  2. SynopsisRésumé
  3. Introduction
  4. Material and methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. References