7/19/2016

1

EVALUATION OF THE IN VIVO WHITENING EFFICACY OF COSMETIC PRODUCTS IN ASIAN SKIN: A REVIEW

OF SKIN TYPES, METHODS AND PERCEPTIONS

13TH JULY 2016, HILTON HOTEL, SINGAPORE

Celine BLANCHE, Spincontrol Asia Co. LTD

INTRODUCTION

• A light complexion is the standard of beauty in Asian cultures and flawless skin is the most universally desired female feature

• Cosmetic claims related to lightening/ whitening effect and evenness of skin tone are amongst the most popular in the Asian market

• Such claims are made for skincare products of all age ranges: women look for a lighter complexion and with age and increased pigmentary disorders, they look for a more even looking complexion (lightening effect and anti-dark spot effect)

• Whitening claims not only apply to facial products but other areas can be targeted: armpit, nipples, intimate area etc.

• Asian skin tends to become darker and more yellow with age, and pigmentary disorders (hyper and hypopigmentation) also become a concern with increasing age

• Several methods are available to evaluate the efficacy of whitening/ lightening and anti-dark spot cosmetic products. Understanding their principle helps choosing the most suitable method for a given cosmetic claim

7/19/2016

2

CONTENT LIST

• Background: skin color and skin ageing

• Notion of skin phototype for Asian skin and reaction of Asian skin to UV light

• Color difference detection: visual perception versus objective measurements

• Available methods to measure skin whitening/ lightening or anti dark spot effect

• Available methods to measure anti dark spot effect only

• Available methods to measure skin tone homogeneity

• Technical considerations for color measurements

• Conclusion

BACKGROUND: SKIN COLOR AND SKIN AGEING

7/19/2016

3

BACKGROUND: SKIN COLOR

• Skin owes its color to the light that it restitutes after an internal journey where a considerable absorption takes place, particularly for some wavelengths

• The spectrum of the retro-diffused light is therefore the inverted absorption spectrum of the skin, which itself depends on the nature and concentration of substances capturing light: chromophores

• Melanin and Haemoglobin are the 2 main chromophores of the skin and the major determinants of differences in skin color between individuals.

• Melanin plays the primary role in coloring the skin

Schematic diagram of the optical pathways of light in skin*

*adapted from Anderson and Parrish

SKIN COLOR: ASIAN SKIN AND SKIN AGEING

• Amongst the 2 types of skin ageing (intrinsic and extrinsic), extrinsic ageing and particularly photoageing is the most visible

• Although wrinkling is a major feature of ageing in some Asian people (ex: Koreans), pigmentary changes are the main features of photoageing for most Asians

• Asian skin becomes darker and more yellow with age (cumulated sun exposure over lifetime) and also displays pigmentation heterogeneity

• The most common pigmented lesions in sun-exposed skin include ephelides (freckles), melasma, lentigo and mottled pigmentation

7/19/2016

4

THE NOTION OF SKIN PHOTOTYPE AND RELEVANCE FOR ASIAN SKIN

• Fitzpatrick skin phototype classification was developed in 1975 as a way to estimate the response of different types of skin to ultraviolet (UV) light

• Skin color from Asian people (Japanese, Chinese and Korean descents) ranges between skin phototype II and V (III to V in Thailand)

• This classification is used by many to represent a subjective scale of pigmentation intensity while it was never intended to do so

• “The individual typology angle (ITA)-based skin color classification correlates with constitutive pigmentation and is physiologically relevant in different geographical areas.”

Fitzpatrick, T.B. (1988) The validity and practicality of sun reactive skin types I through VI. Arch

Dermatol 124; 869-871.

THE NOTION OF SKIN PHOTOTYPE AND RELEVANCE FOR ASIAN SKIN

S. Del Bino and F. Bernard: Variations in skin colour and the biological consequences of ultraviolet radiation exposure. British Journal of Dermatology. 2013, 169 (Suppl. 3): 33-40

Classification of skin color based on the ITA°

value

7/19/2016

5

REACTION OF ASIAN SKIN TO UV LIGHT

• Companies willing to sell their sunscreens in Asia should be assessing the Sun Protection Factor in order to know the level of protection on such skin type

• Current applicable guidelines (ISO 24444, FDA 2011, International Method 2006) recommend to recruit subjects of phototype I to III and ISO 24444 even recommends to have a mix of the 3 types

• This is incompatible with Asian skin which ranges from phototype III and up mainly

• Moreover it is hard for them to answer the questionnaire related to skin phototype determination (avoided sun exposure, no real winter season etc.)

• This poses the problem of compliance with the current guidelines, notably in terms of mixing skin phototypes in each test (I, II and III)

C. Courbiere et all, Expression Cosmétique, Guide 2015

REACTION OF ASIAN SKIN TO UV LIGHT

• Objective: To show how compliance to the current SPF guidelines could be an issue when SPF is determined in Asian skin

• Methodology: Compare results from unprotected MED readings from Caucasian (Romania) and Asian (Thailand) subjects

• Results: Typological data of the 2 panels show that the erythemal sensitivity according to ITA° angle are quite superimposable except for Caucasian data with ITA°>55 which are mostly type I and II.

C. Courbiere et all, Expression Cosmétique, Guide 2015

Conclusion: Subjects selection using ITA° angle seems more suitable when performing SPF studies in Asians. It would be preferred to have the selection of subjects per ITA° angle as the main criterion

Skin type Mean ITA°

Mean MED

ITA° Min

MED Min

ITA° Max

MED Max

EUROPEAN DATA

I 64.4 15.1 58.6 12.0 70.2 19.6

II 49.0 26.4 29.0 13.4 66.5 42.0

III 42.5 29.2 28.4 15.8 57.4 48.9

General mean

45.2 27.9 28.4 12.0 70.2 48.9

ASIAN DATA

III 38.8 28.6 31.0 20.0 50.2 42.6

7/19/2016

6

COLOR DIFFERENCE DETECTION: VISUAL PERCEPTION VERSUS OBJECTIVE MEASUREMENTS

SUPPORTING LIGHTENING CLAIMS: OBJECTIVE EQUIPMENT VERSUS CONSUMER’S PERCEPTION

• Supporting whitening claims can be made using several devices

• Due to the sensitivity of such devices, the significant whitening effect that they depict might not be visible to the endpoint consumers of the product

• The magnitude of the lightening effect necessary to be perceptible for human observers is not known

• Objective: evaluate the perceptibility threshold (also called just noticeable difference in psychophysics) of skin color differences along the L* and b* directions in the CIELAB color space as well as for the Individual Typological Angle ITA° and color difference E*

• Note: this evaluation was done on Asian male and female subjects

F. Perin et all: In vivo evaluation of the just noticeable skin whitening effect in Asian subjects; poster IFSCC Bangkok 2011

7/19/2016

7

WHEN DOES A SIGNIFICANT LIGHTENING EFFECT BECOME VISIBLE TO THE CONSUMER?

• Methodology:

Blindly presenting simultaneously 2 stimuli to 3 observers (250 evaluations performed)

Stimuli: two 16 cm2 skin areas (inner forearms)

2 skin areas presented side-by-side under standardized lighting (sometimes from same subject and sometimes from 2 different persons)

Each observer was asked to select the “darker” skin area

Chromametry measurements were made at the same locations to define which presented skin site was truly the darker one

If the site selected as darker by the observer corresponded to the darker site as shown by chromametry, then a score of +1 was attributed to the evaluation. If incorrect, a score of 0 was given

F. Perin et all: In vivo evaluation of the just noticeable skin whitening effect in Asian subjects; poster IFSCC Bangkok 2011

WHEN DOES A SIGNIFICANT LIGHTENING EFFECT BECOME VISIBLE TO THE CONSUMER?

F. Perin et all: In vivo evaluation of the just noticeable skin whitening effect in Asian subjects; poster IFSCC Bangkok 2011

Relative sigmoid curve between delta L* and average points of evaluation

Relative sigmoid curve between delta b* and average points of evaluation

0.61 0.87

7/19/2016

8

WHEN DOES A SIGNIFICANT LIGHTENING EFFECT BECOME VISIBLE TO THE CONSUMER?

F. Perin et all: In vivo evaluation of the just noticeable skin whitening effect in Asian subjects; poster IFSCC Bangkok 2011

Relative sigmoid curve between delta ITA and average points of evaluation

Relative sigmoid curve between delta E and average points of evaluation

3.37 1.57

WHEN DOES A SIGNIFICANT LIGHTENING EFFECT BECOME VISIBLE TO THE CONSUMER?

• Results:

Average scores and percentages of correct responses were plotted versus the color differences between the two stimuli (L*, b *, ITA° and E*)

To be consistently perceived by human observers, the differences in the color parameters under investigation must be 0.61 for L*, 0.87 for b*, 3.37° for ITA° and 1.57 for E* in Asian subjects

Based on our experience, these perceptibility thresholds are generally superior to the variations induced by most lightening treatments.

F. Perin et all: In vivo evaluation of the just noticeable skin whitening effect in Asian subjects; poster IFSCC Bangkok 2011

7/19/2016

9

AVAILABLE METHODS TO MEASURE SKIN WHITENING/ LIGHTENING AND ANTI DARK SPOT EFFECT

REFLECTANCE COLORIMETRY

• Measuring principle: Based on tri-stimulus method (similar to human color perception). White light on the skin and collection of retro-diffused light and measured after filtering through 3 colors: red, green and blue (RGB)

• CIE (Commission Internationale de l’Eclairage) L*a*b* color space

• Probe diameter: 8mm (complexion mainly) probe aperture

• Output: L*, a*, b* parameters (and calculation of ITA° angle)

• Commercially available device: Chromameter CR-400 (Minolta, Japan)

7/19/2016

10

INTERPRETATION OF COLORIMETRY PARAMETERS

• L* represents the relative brightness from total black (L*=0) to total white (L*=100)

• a* represents the balance between red and green

• b* represents the balance between yellow and blue

• ITA°: Individual Typological Angle

ITA° = Arctg [(L* - 50)/b*] . (180/π)

• Combination of L* and b* to describe a whitening-lightening effect using ITA° value (b* itself relevant for Caucasian skin but not Asian skin)

* Petit L, Pierard GE. Skin-lightening products revisited. International Journal of Cosmetic Science, 2003; 25: 169-181

SPECTROPHOTOMETRY

• Measuring principle: based on physical measurement of reflected light at specific wavelengths (400-700 nm), corresponding to the spectrum of visible light.

• Probe diameter: 3mm (dark spot) or 8mm (complexion) probe aperture

• Output: For skin color measurements the device is used as a colorimeter and color is expressed within the L*a*b* system; calculation of ITA° angle and Delta E (color contrast dark spot/ adjacent skin when both are measured)

• Commercially available device: Spectrophotometer CM 700d (Konica, Japan)

7/19/2016

11

NARROW-BAND REFLECTANCE COLORIMETRY

• Measuring principle: absorption/reflection and measurement at specific wavelengths corresponding to the spectral absorption peak of haemoglobin (erythema) and different pigments (melanin).

• Probe diameter: 5mm probe aperture (complexion or dark spot)

• Output: Melanin index (MI) and Erythema index (EI)

• Commercially available device: Mexameter® MX18 (Courage & Khazaka, Germany)

• Note: correlation EI with a* parameter from L*a*b* system

COMBO-TYPE COLORIMETERS

• Measuring principle and output: Colorimeter with the possibility to obtain L*a*b* values from CIE system or Erythema Index and Melanin index

• Probe diameter: 5mm (complexion or dark spot) to 8mm probe aperture (complexion mainly)

• Commercially available devices: DSM II ColorMeter (Cortex technology, Denmark), SkinColorCatch (Delfin, Finland)

SkinColorCatch

DSM II ColorMeter

7/19/2016

12

VISIBLE SPECTRUM REFLECTANCE COLORIMETER

• Measuring principle: Diode emitting in the full visible spectrum. The photodetector measures the globally reflected light to compute erythema as well as melanin values

• Probe diameter: 5mm probe aperture (complexion or dark spot)

• Output: Melanin index (MI) and Erythema index (EI)

• Commercially available device: Dermacatch (Colorix, Switzerland)

DIGITAL PHOTOGRAPHY AND IMAGE ANALYSIS (1/2)

• High-resolution digital photographs taken under reproducible conditions (using cross-polarized light) can be further analyzed to measure color changes of the complexion and dark spots

• RGB values are extracted from the area of interest on the digital photograph to measure the necessary parameters

• Commercially available device: VISIA-CR (Canfield, US)

VISIA-CR Visio Face system from Spincontrol

7/19/2016

13

DIGITAL PHOTOGRAPHY AND IMAGE ANALYSIS (2/2)

• Output: Several parameters can be measured from the digital photographs to assess the color of skin complexion:

Color analysis:

- Color of dark spot(s) and/ or adjacent normal skin (L*, a*, b* and ITA° parameters)

- Difference of color (∆E*ab) between the spot and the skin (if measuring dark spot and adjacent skin)

Melanin intensity and illustration of product’s efficacy before/ after

Cross-polarized photograph

Melanin mapping

CLINICAL EVALUATION/ VISUAL SCORING

• The human eye is incapable of measuring (i.e. quantifying) skin color but it can very accurately detect color difference, especially when colors are placed side-by-side

• Scoring of skin color can be done using color charts or color scales, with colors ranging from light beige (skin complexion scoring) to dark brown (scoring of dark spot color)

• Evaluation is performed by a trained assessor

• Clinical evaluation is between instrumentation and subjective evaluation by a panel: relates to visual effect seen by future consumers but done in a more accurate and reproducible way than subjective evaluation

• Limitation: Hard to grade skin color if skin tone is too heterogeneous

*De Rigal et al.: Development and validation of a new Skin Color Chart; SRT 2007; 13: 101–109

Skin Color chart* to score skin complexion

and dark spot

Color saturation scale to score skin complexion

and dark spot

7/19/2016

14

AVAILABLE METHODS TO MEASURE ANTI DARK SPOT EFFECT ONLY

DIGITAL VERNIER CALIPER (DARK SPOT SIZE)

• Principle: Measurement of the largest diameter of one well-defined dark spot before treatment, and successive measurement of the same diameter (same orientation) throughout the course of the study

• Quick, cheap and easy to perform, even though repositioning is a critical parameter to control and requires a lot of practice

• Resolution: 0.01 mm and accuracy: ±0.02 mm

• Output: dark spot diameter in mm

Digital Vernier Caliper

7/19/2016

15

DIGITAL PHOTOGRAPHY AND IMAGE ANALYSIS (DARK SPOT SIZE AND COLOR)

• High-resolution digital photographs can also be used to follow the evolution of dark spots reduction after product application.

• Output: Several parameters can be measured from the digital photographs:

Morphology analysis: Number Area (pixels²) and perimeter (pixel) of the dark spot(s) of spots on the cheek

Contour analysis: Difference of color (∆E*ab) between the most internal contour and the most external contour; Sharpness of the contours

Illustration of dark spots reduction after product

application

¾ view cross-polarized

photograph used for dark spot analysis

UV-REFLECTANCE PHOTOGRAPHY

• Principle: Use of UV-reflectance photography to observe areas of pigment density below the skin surface (~3mm) which are difficult to see or invisible under normal light

• Used for illustration more than for quantification, chromophore mapping

• Commercially available device: VISIA-CR (Canfield, US) and RBX technology

Digital photograph taken using VISIA-CR® and UV-fluorescence light

7/19/2016

16

• Clinical evaluation is performed by one trained judge using a photographic scale

• Using a photographic scale increases the reliability of evaluation of the assessed parameter

• This relates to a visual effect that consumer can expect to notice themselves

• Evaluation performed under controlled conditions: ambient conditions, lighting conditions (daylight), position of the volunteer, position of the technician and photographic scale, clothing and hair covered etc.

• Commercially available scale: Skin Ageing Atlas vol. 2: Asian type (R. BAZIN, MED’COM 2010)

ANTI-DARK SPOT EFFICACY USING CLINICAL EVALUATION (PHOTOGRAPHIC SCALES)

ANTI-DARK SPOT EFFICACY USING CLINICAL EVALUATION (PHOTOGRAPHIC SCALES)

• Scale available to assess dark spots density on the cheek area

• Possibility to give intermediate grades (.4 and .6)

• Scales available for both genders

• Atlas specifically developed for Asian skin

• Small differences in dark spots density can be detected

Photographic scale showing severity of dark spot density*

*Ref. of the scale: Skin Ageing Atlas vol. 2: Asian type (R. BAZIN, MED’COM 2010), pp.80-81

7/19/2016

17

NOTE: ANTI-MELASMA AND POST-INFLAMMATORY HYPERPIGMENTATION (PIH) MEASUREMENT

• Melasma is a common facial pigmentary disorder amongst Asian women (40% of Thai women)

• Acne is also a common skin problem amongst Asian people, and not only teenagers

• People with darker skin are more prone to developing PIH, and strong sunlight in this region therefore makes the occurrence of PIH higher, notably following resolution of inflammation from acne lesions

• The methods previously presented can be used to assess product’s efficacy at reducing the intensity of melasma and PIH (acne scars etc.)

AVAILABLE METHODS TO MEASURE SKIN TONE HOMOGENEITY

7/19/2016

18

DIGITAL PHOTOGRAPHY AND IMAGE ANALYSIS

• Measurement of skin tone homogeneity using co-occurrence matrix method

• Cross-polarized photographs are converted into blue channel first

• Calculated co-occurrence parameters: entropy of co-occurrence matrix and inverse difference moment (homogeneity):

Entropy corresponds to a human visual perception of granulation

Inverse difference moment corresponds to the texture homogeneity

Cross-polarized picture (left)/ Blue channel picture (Right)

SELF-ASSESSMENT USING QUESTIONNAIRE

• Questions asked to the volunteers using the test product about the whitening/ lightening/ anti-dark spot effect of the product

• Subjective evaluation which reflects consumer feedback

• The evaluation can be done in more or less standardized conditions: daylight lamp, cover over subject’s clothing and hair, checking that the questionnaire is fully completed by volunteers

• It is also possible to keep all in normal conditions of use: questionnaire answered by the volunteer at home

• Recommended to combine this evaluation with other methods to have a more complete information about product’s performance and acceptability

7/19/2016

19

TECHNICAL CONSIDERATIONS FOR COLOR MEASUREMENTS

EQUIPMENT AND OPERATOR-RELATED PARAMETERS

• For visual evaluation:

Illuminant should be daylight

Repositioning of test site between each visit to ensure same site is measured each time (stencils, skin marking etc.)

Training of the technicians and maintenance of expertise

• For digital photography:

use of room with black painted walls and color checker (calibration)

• Contact methods:

Pressure of the probe on the skin (blanching effect), linked with ergonomy and control of the technician’s position at each visit

Measured area limited to probe aperture size

7/19/2016

20

VOLUNTEER-RELATED PARAMETERS

• Acclimatization to laboratory ambient conditions (20-24°C, 40-60% RH) during at least 20min (if measurements on the body: test site uncovered during this period)

• Position of the subject during measurements: influence of blood flow (prone position)

• Volunteer’s diet: influence of spicy food, coffee and tea intake on skin color

• Circadian rhythms: measurements should be made at the same time of the day for each visit (±2h)

• For visual evaluation: cover subjects’ clothing with black cover (influence from extrinsic colors)

• Presence of excessive hair on the test site (beard on face for men, outer forearm etc.)

• Note: subject’s compliance (characteristics of the tested product: texture, fragrance, color etc.)

POSSIBLE EFFECTS FROM EXTERNAL FACTORS

• Effects of the seasons: while Asian countries record strong sunlight all year long, seasons and behaviors can impact on the subjects’ skin color

• Cultural events: Ex: Thailand, Songkran festival in mid-April (water festival, involuntary sun exposure)

• Ambient conditions in the testing laboratory: in Thailand we can control them within 20-24°C and 40-60%

• Note: Guidelines about clinical testing written by Europeans and Americans (conditions not always suitable to perform studies in Asia such as ambient conditions)

7/19/2016

21

RELEVANCE TO USE UNTREATED CONTROL SITE IN SKIN WHITENING STUDIES PERFORMED IN ASIA

• Effects of volunteer’s behavior on skin color

• Strong sunlight all year long, even though Asian people tend to flee the sun

• Lack of awareness of effects of UVA on the skin: increased outdoor activities during rainy season (forecast weather) and lower sun protection during this period

• It is crucial to have an untreated control site for skin whitening studies (except if testing whitening armpit product for example)

• However, not always possible to have an untreated control site: ethical aspect of testing a whitening facial product with split-face design over 2 months, volunteers wearing hijab in Muslim countries such as Indonesia (neck and forehead partially covered)

CONCLUSION

• The Fitzpatrick’s skin phototype classification is over used to identify people’s skin tone while it was initially developed to define their sensitivity to the sun. Moreover the requirements from current SPF guidelines should be reviewed when evaluating the SPF in Asian subjects

• Many methods are available to assess the efficacy of cosmetic products which improve skin tone and pigmentation disorders. The choice of the method depends on the expected claims, budget and type of product tested

• b* parameter is not suitable to assess whitening effect in Asian skin

• Clinical significance versus statistical significance

• While equipment detect very small differences in skin color, changes in skin color must be visible to the consumers (combining methods is recommended)

7/19/2016

22

THANK YOU FOR YOUR ATTENTION