Efficacy Methodology and Assessment of Cosmetics R. Randall Wickett University of Cincinnati College...

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Efficacy Methodology and Assessment of Cosmetics

R. Randall WickettUniversity of CincinnatiCollege of Pharmacy

randy.wickett@uc.edu

Outline of Topics• Non-invasive measurements of skin function

– Transepidermal Water Loss– Electrical Measurements– Mechanical Measurements– Skin Color– Surface Analysis

• Protocols for Efficacy Assessment– Moisturizer Efficacy– Cleanser Mildness– Anti-aging products

Utility of Non-invasive Bioengineering Measurements

• Why not just rely on visual grading?• Grading is not “objective”• Grading is not “reproducible” at an exact level.

Agreement within ± 0.5 grades units is considered very good.

• Bioengineering Tools can give additional information. For instance visual grades will not necessarily tell you if skin is more or less elastic or if the skin barrier is perturbed.

• Bioengineering measurements can be used to support claims and for guiding the product development process

• Training and experience are required to obtain valid and reproducible bioengineering measurements

Ronald Marks, M.D.

• One of the “Godfathers” of bioengineering measurement on skin

• Organized the first symposium on noninvasive methods and the skin in 1976 and founded ISBS

Albert M. Kligman, M.D.

• Another Godfather of Skin Bioengineering – first talked about the possibility of admitting a “blind person” as a dermatology resident.

• A fool with a tool is still a fool

General Considerations for non-invasive measurements on skin

• There are no published standard protocols similar to ASTM (American Society for Testing Materials)

• “Guidances” are published by EEMCO (European group on Efficacy Measurements of COsmetics and other topical products) for various categories of methods

General Recommendations for instrumental measurements on Skin

• Some control of testing environment is necessary to prevent sweating– Normally 20 ± 1 C, 30-45% RH

• Subjects should equilibrate 30 minutes if possible• Subjects should avoid drinking hot coffee or tea or

eating for at least 1 hour prior to measurement• Subjects should avoid uncontrolled use of cosmetic

products on the measurement sites for at least 1 week prior to measurement

• Subjects with any obvious skin disease, tattoos or injury in the treatment area will be excluded.

Transepidermal Water Loss

• Water transport through the skin by passive diffusion

• Rate is 5-10 g/m2/hr in healthy skin• Increases with surfactant damage• Used to measure occlusion by products• Used extensively in barrier disruption and repair

studies• Panelists must not be sweating. Equilibrate 30 min.

at ~21C RH<50%

The Dermalab Evaporimeter

The C+K devices

TEWA Meter probe

Corneometer probe

Sebumeter

Cutometer probe

The operating principle of open chamber TEWL devices

Forearm Controlled Application Test (FCAT)

• Lather wetted bar for 6 seconds with Masselin towel

• Transfer lather to site and wash for 10 seconds

• Leave lather in place 90 seconds• Rinse for 20 seconds• Repeat 4X daily for one week

Forearm washing

Washing and rinsing

Forearm wash test bars

• Bar 1 mild syndet + oatmeal

• Bar 2 mild syndet + oatmeal

• Bar 2 mild syndet

• Bar 4 Soap pure soap

• Bar 5 Soap + humectant

Measuring TEWL after a forearm wash test

TEWL: Forearm wash test

RR Wickett, Forearm wash testing of mild soap bars containing colloidal oatmeal, Canadian Chemical News, 49(1), 22-23 (1997).

Redness grade versus TEWL: Forearm Wash Test

Electrical Measurements of Skin

• Skin lipids have a low dielectric constant, water has a high dielectric constant.

• When skin is hydrated conductance and capacitance (reactance) increase and impedance decreases.

• Used to estimate water content of stratum corneum.

The NOVA DPM

The Skicon

Correlation with dry skin grades

• Dry skin is lacking in moisture.• Several studies have shown that electrical

measurements correlate with dry skin grades as expected

• Morrison and Scala correlated Correlated Corneometer and Skicon readings to flaking grades on dry hands scores that developed as subjects washed their hands for 1 minute five times a day for 4 days.

• We also have data on correlation of readings of all three instruments to dry skin grades on the legs.

Correlation between Flake Grade and Corneometer CM 820 values

Morrison and Scala(1996) J. Toxicol-Cut.& Ocular Toxicol, 15:305-314 15

Skicon versus mean flaking grade

Morrison and Scala(1996) J. Toxicol-Cut.& Ocular Toxicol, 15:305-314 15

Grading scale for dry skin, half grades are allowed

Grade Description

0 No scaling

1.0 Slight powdery appearance and occasional patches of small scales widely distributed

2.0 Small scales in combination with a few larger scales, slight roughness, whitish appearance

3.0 Small and large scales uniformly distributed, definite roughness and possible a few superficial cracks

4.0 Dominated by large scale, rough, redness present and eczematous changes

F Li, MO Visscher, E Conroy and RR Wickett, J. Cosmet. Sci. 52, 23-33 (2001).

Scatter plot of Skicon reading versus Dry Skin Grade

R. R. Wickett and F. Li Unpublished Data

Average values versus dry skin grades Skicon and Corneometer

R. R. Wickett and F. Li Unpublished Data

Average values versus dry skin grades NOVA meter

R. R. Wickett and F. Li Unpublished Data

Brancaleon et al. correlated Skicon readings with ATR-FTIR measurements of water in the SC. “Our attempt to link the hydration measured withATR-FTIR to the hydration measured with the Skiconhygrometer shows a high degree of correlation. This is not unexpected as both instruments record superficial hydration.”

Correlations among instrumental measurements

SKICON VS CORN

0

50

100

150

200

250

300

350

0 20 40 60 80

r =0.8741

NOVA VS SKICON

0

50

100150

200

250

300

350400

450

500

0 50 100 150 200 250 300 350

r =0.9347

NOVA VS CORN

0

50100

150200

250

300350

400450

500

0 10 20 30 40 50 60 70 80

r =0.8873

F. Li, et. Al J. Cosmet. Sci. 52, 13-22(2001).

Correlations between instruments

Clarys et. al. Fluhr et. al. Our work*

NOVA vs Skicon 0.96 0.96 0.93  NOVA vs. CM 0.97 0.82 0.87 Skicon vs. CM 0.89 0.83 0.89 

Clarys, P., et al Skin Res Technol, 5, 14(1999).

Fluhr, J. W., et al Skin Res. and Technol., 5, 171 (1999).

Li, F. et al J. Cosmet Sci 52, 13-22 (2001)

Electrical measurements and moisturizer claims

• For more than 20 years electrical measurements made within 30 minutes to a few hours of treatment have been used to substantiate claims of moisturizing efficacy.

• We have reported that measurements made at one hour predicted moisturizing in a two week test for formulations containing glycerin from 0 to 15% concentration. (Li et al J Cosmetic Science, January 2001)

Effect of moisturizers on DPMEffect of moisturizers on DPM(Formulations from ~ 1990)(Formulations from ~ 1990)

Correlation TestGoal determine the correlation between one hour device readings and effects on skin grades in a dry skin test:

One hour Test: 9 subjects

Two week test: 20 subjects

subjects were female, between the ages of 18 and 57 and in good general health with no known skin diseases.

Products contained 0, 5, 10 and 15% Glycerin in identical base

Each subject used each of the 4 products on their legs

DEVICE PREDICTION CAPABILITY: SKICON

ONE-WEEK SKIN SCORE REDUCTION VS ONE-HOUR SKICON MEASUREMENT(CHANGES FROM BASELINE): SKICON PREDICTION CAPABILITY

y = 0.0024x + 0.8118R2 = 0.9681

0.5

0.7

0.9

1.1

1.3

1.5

0 50 100 150 200 250 300 AU

SC

OR

E

 Device Regression equation R-square p

NOVA G = 0.0025x + 0.69 0.92 0.04

SKICON G = 0.0024x + 0.81 0.97 0.02

CM 825 G = 0.0209x+ 0.76 0.84 0.08

Regression equations of one week skin grade versus one hour electrical measurements

We do not consider the difference between instruments to be meaningful.

Conclusion

• Single point or short term electrical measurements have been shown to be predictive of long term moisturization for simple formulations using on GlycerinGlycerin as a moisturizer.

F Li, MO Visscher, E Conroy and RR Wickett, J. Cosmet. Sci. 52, 23-33 (2001).

Mechanical Properties of Skin

• There are two fundamental ways to measure the mechanical properties of an object– Apply a known strain and measure the stress– Apply a known stress and measure the strain

• Most skin instruments use the second approach

The Cutometer 575

The Cutometer probe

An optical system is used to measure the height that the skin rises into the probe

The optical system of the Cutometer

Picture courtesy of Courage + Khazaka GmbH

The Cutometer 575 probe

Cutometer curves

Cutometer Parameters

• UE is the elastic deformation of the skin due to the application of stress (vacuum or torque) by the instrument; 

• UV is the viscoelastic creep occurring after the elastic deformation; 

• UF is the total extensibility of the skin;

• UR is the elastic deformation recovery due to stress removal; 

• UA is the total deformation recovery at the end of the stress-off period;

• R is the amount of deformation not recovered by the end of the stress-off period

Cutometer curves

An illustration of the Cutometer curve and analysis (from C+K)

See RR Wickett, Stretching the Skin Surface Cosmetics and Toiletries 116(3), 47-54(2001) for details of Cutometer and DTM analysis

Ratio Parameters

• UA/UF is the overall elasticity of the skin including creep and creep recovery;

UR/UE is the pure elasticity ignoring viscoelastic creep; 

• UV/UE is the ratio of viscoelastic to elastic extension called the viscoelastic ratio;

 • UR/UF is the ratio of elastic recovery to total

deformation.

Issues with mechanical measurements

• What part of the skin are we measuring?– General principle: to measure the stratum corneum use

the smallest feasible deformation– To measure the dermis use a larger deformation

• Interpretation of data– For moisturization we can look increased Ue and Ur

reflecting increased elasticity.– Many anti-aging treatments claim “firmness” but there

is no engineering definition of firmness

Extensibility of shoulder skin v.

ageCutometer Uf

6 mm diameter probe

Lola Kelly Smalls Ph.D. dissertation University of Cincinnati

Smalls LK, Wickett RR, Visscher M, Effect of Dermal Thickness, Tissue Composition, and Body Site on Skin Biomechanical Properties, Skin Research and Technology, 12 43-49 (2006)

Parameter Pre-treat Post-Treat P-value

NOVA DPM 98.8 116.2 0.001

Ue (200) 0.036 0.048 0.02

Ue (500) 0.068 0.079 0.46

Uv (200) 0.015 0.024 0.07

Uv (500) 0.025 0.029 0.60

Ur (200) 0.026 0.039 0.03

Ur (500) 0.050 0.061 0.26

Effect of vacuum level on Cutometer sensitivity to 1 week of treatment with a moisturizer with limited efficacy

Wickett, RR (2001) Cosmetics and Toiletries 116, 47-54

D’Squames® are an easy way in investigate skin scaling and flaking

They can be graded visually or analyzed by computer

The computer can calculate the Desquamation index (D.I.)

Schatz, et al. J. Soc Cosmet. Chem. 44, 53-63, 1993

6

12..

5

1

n

n nTAID

A = percent area covered by scalesTn = percentage of scale at each thickness leveln = thickness level 1 to 5

We found blacks to have higher visual dryness scores than whites, especially on legs

Warrier(1996) et al J. Soc. Cosmet. Chem. 47, 229-240

D.I. showed the opposite

Warrier(1996) et al J. Soc. Cosmet. Chem. 47, 229-240

The Minolta Chromameter

Color is measured on the L* a* b* scale.

L* = white 0 to 100

a* = red – green 60 to –60

b* = blue – yellow –60 to 60

Using the Chromameter

The color wheel

The color solid

Minolta a* in forearm wash testa* Forearm wash test

0

1

2

3

Bar 1 Bar 2 Bar 3 Bar 4 Bar 5 Water

Bar

a*

RR Wickett, Canadian Chemical News, 49(1), 22-23 (1997).

Correlation between a* and erythema grade in the FCAT

Chromameter L values for various ethnic groups

Alaluf et al (2002) Pigment Cell Res.

Analysis of skin surface textureSilicone replicas are most commonly used

Obtaining a replica from

the peri-orbital

(crows foot) area

Photo courtesy of Ken Marenus

Image analysis can quantify wrinkle depth by the shadow principle

Corcuff et. Al. JSCC 34 177-189 (1983)

Replicas of young and old forearm skin montage

Replicas from the “crows foot” area of the eye

Crow’s foot wrinkle depth versus age

Corcuff et. Al. JSCC 34 177-189 (1983)

Visiometer

• Replicas are died blue

• Light transmission is measured to determine the depth of the lines

Visiometer

Microrelief of the skin determined by the visiometer

Fringe Projection (PRIMOS)

• Phase Shifting Rapid In vivo Measurement of Skin

• Digital micromirror device used to project fringe pattern on the skin surface

• CCD camera records image• Shifting of the fringe patterns by surface

contour allows 3D imaging

Primos measurement on the face

Distortion of fringes by wrinkles

Grey scale coded 3D image

Line profile from the Primos

The VISIA imaging system by Canfield allows for capture of high quality images of the face using different types of light

Image analysis can be performed to pick out hyperpigmented spots and other features of photoaging

Image of face with spots highlighted

Photo courtesy of Greg Hillebrand, used with permission

Moisturizer Testing

• Regression and “mini” regression tests

Regression testing of moisturizers

The ‘Gold Standard’ test of moisturizer efficacy

Three weeks of treatment followed by two weeks of regression

The goal is to separate out the visual effects of the product and show only the real effect on skin physiology

Better moisturizers will be better in the regression phase

Kligman, Cosmetics and Toiletries April 1978 27-35

Rogers et al JAAD 21 714 (1989)

Regression test with Petrolatum

Kligman, Cosmetics and Toiletries April 1978 27-35

Regression test with “Cosmetic” and “Therapeutic” Moisturizers

From Rawlings et al Derm Ther (2004) 17 49-56

The ‘mini’ regression test: One or two week treatment phase, one week to a few days regression. By comparing products on the same panelist and using instruments better sensitivity can be achieved with fewer subjects and a shorter treatment time.

Pretreatment

End of treatment End of Regression

Grove has used 4 day “mini-regression” protocols with grading and conductance measurements on dry legs

• Products applied to 2x2 cm area by trained staff

• Conductance measured with Skicon

• 19 female subjects• Two week washout• Lotions separated in

conductance readings but were not significantly different by skin grade

G. Grove et al poster presentation product names removed used with permission

Rawlings combined visual dryness with Corneometer readings in a 3 day mini regression test

Rawlings et al Derm Ther (2004) 17 49-56

Testing “Ant-Aging” products

Clinical Features of Photo-Aging

• Lines and Wrinkles

• Loss of Elasticity

• Elasticity becomes more anisotropic

• Appearance of “Age Spots”

Methods for evaluation of anti-aging products

• Clinical grading directly on panelists• Grading of high quality clinical photographs• Analysis of replicas• Mechanical measurements• Primos system to analyze wrinkles• VISIA System• Biopsies to evaluate changes in dermal histology

Descriptive grading scale for photoaging

Griffiths et. Al. (1992) Arch Dermatol.;128:347-351

Photographic Grading Scales

• There are several different photographic grading scales

• Griffiths et. Al. (1992) Arch Dermatol.;128:347-351• Larnier et. Al. (1994) Brit. J. Dermatol130. 167-173• Chung (2003)Photodermatol Photoimmunol

Photomed 19: 109–121

The grading scale by Griffiths et. Al. is probably the most commonly used.

The Larnier scale 4 -6

Chung’s scale with Korean subjects

Anti-Aging Studies: General Considerations

• Anti-aging effects take time to demonstrate.• Studies usually run for about 24 weeks and 12 weeks

seems to be a minimum.• Facial studies are usually monadic. That is each

subject tests only one product.• Studies on forearms may be done as paired

comparisons. • Studies must be done double blind.• Vehicle (placebo) Effects can be quite large.

Moisturizing vehicles will produce noticeable effects on fine wrinkles and avoiding sun will improve grades.

A reason for not doing split-face studies on anti-aging products

I’ve been part of a 15 year study on

sunscreens. Every day I put SPF 30 on one side of my body and nothing on the other side

Outline for anti-aging test on facial product

• 60 female subjects with moderate photodamage on the face.

• Randomized or balanced into two groups of 30, active and vehicle or placebo.– Subjects and graders/measurement technicians are blind to the

treatment

– Treatment is to whole face

– Forearms are also treated for biopsies

• Measurements made at baseline and after 3 and 6 months of treatment.

Measurements anti-aging test• Grading.• Clinical photographs or VISIA system.• Cutometer readings on cheek.• Replicas taken from crows foot area of eye for

image analysis or PRIMOS measurements made in eye area.

• Biopsies taken from forearm at baseline and 6 months only for collagen and elastin measurement (this is definitely optional)

Minimum requirements• The test I have described could be called a Cadillac

test as it has a lot of options• At the minimum grading and clinical photographs

should be obtained. • Some studies run for only 3-4 months and

occasionally they are done split face• Pilot studies may be done on photodamage forearms

using both male and female subjects and in this case one arm will get vehicle and the other treatment.

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