EVALUATION OF THE IN VIVO WHITENING EFFICACY OF

7/19/2016
EVALUATION OF THE IN VIVO
WHITENING EFFICACY OF COSMETIC
PRODUCTS IN ASIAN SKIN: A REVIEW
OF SKIN TYPES, METHODS AND
PERCEPTIONS
Celine BLANCHE, Spincontrol Asia Co. LTD
13TH JULY 2016, HILTON HOTEL, SINGAPORE
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
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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
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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
Schematic diagram of the optical
pathways of light in skin*
• 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
*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
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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
Classification of skin
color based on the ITA°
value
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
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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.
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
C. Courbiere
et
all, Expression
Guide
III
38.8
28.6 Cosmétique,
31.0
20.02015 50.2
42.6
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
ASIAN DATA
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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
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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?
Relative sigmoid curve between delta L* and average
points of evaluation
0.61
Relative sigmoid curve between delta b* and average
points of evaluation
0.87
F. Perin et all: In vivo evaluation of the just noticeable skin whitening effect in Asian subjects; poster
IFSCC Bangkok 2011
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WHEN DOES A SIGNIFICANT LIGHTENING EFFECT BECOME
VISIBLE TO THE CONSUMER?
Relative sigmoid curve between delta ITA and average
points of evaluation
3.37
Relative sigmoid curve between delta E and average
points of evaluation
1.57
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?
• 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
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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)
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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)
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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)
DSM II ColorMeter
SkinColorCatch
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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
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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)
Cross-polarized photograph
- 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
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 sideby-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
Skin Color chart* to
score skin complexion
and dark spot
• 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
Color saturation scale to
score skin complexion
and dark spot
*De Rigal et al.: Development and validation of a new Skin Color Chart; SRT 2007; 13: 101–109
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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
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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 crosspolarized
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
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ANTI-DARK SPOT EFFICACY USING
CLINICAL EVALUATION
(PHOTOGRAPHIC SCALES)
• 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)
• 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
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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
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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):
Cross-polarized picture (left)/
Blue channel picture (Right)
 Entropy corresponds to a human visual perception of granulation
 Inverse difference moment corresponds to the texture homogeneity
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
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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
site is measured each time (stencils, skin marking etc.)
same
 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
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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)
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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)
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THANK YOU FOR YOUR
ATTENTION
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