How to Evaluate the Exfoliating Effect of a Cosmetic Product? Review of the methods by Anne Charpentier

July 22th

Direct Link

http://cosmetics.specialchem.com/tech-library/article/how-to-evaluate-the-exfoliating-effect-of-a-cosmetic-product

Exfoliate is derived from the latin word exfoliare which means, to strip and remove thin surfaces of something. In the field of Cosmetology, it refers to removing the dead cells from the superficial layers of the epidermis, the Stratum Corneum.
Indeed, the differentiation of the cells of the epidermis from the dermo-epidermal junction to the upper layers of the epidermis represents a renewed dynamic environment material.
In dermatology, this phenomenon of exfoliation is also linked to desquamation. The term flaking, refers to the corneocytes loss induced by diseases or external aggressions.
Exfoliation eliminates the old cells and let the new ones emerge with the intrinsic cycle of epidermis renewal. Read on to find out how to evaluate the exfoliation effect of cosmetic products.

How to Assess the Exfoliating Effect?

Exfoliation indirectly increases the renewal of the epidermis and its oxygenation / homogeneity of the skin complexion. Exfoliating products act mechanically or chemically to actively clean and purify the skin, making it softer.
But what about evaluating the exfoliating effect of a cosmetic product? Are there any methods or devices to put forward that can help us evaluate the exfoliating effects?
To classify the different choices of methods and tests, we need to look at (readability!) both qualitative and quantitative measurement of this claim . Of course, the “quantitative” evaluation measures parameters and meets the answer to the “what”, while the “qualitative” brings a visual approach and responds to the “how”. Sometimes the evaluation with repeated visual approach enables obtaining a a semi-quantitative approach.
Let’s take a look at different methods that can help you test the efficiency of an exfoliant.

The database of the in human efficacy testing, skinobs.com lists more than 15 methods, in addition to others that include consumers testing, clinical scorage and sensory analysis.

Here is a brief summary of the results we can identify in the database after searching for the claim “exfoliating”.

Direct	Studied effect	Quantitative	Semi-quantitative	Qualitative
	Corneocytes removal	Quanti Squame (Monaderm)	Antera 3D (Miravex), Sonde Raman (Horiba Jobin), Vivascope (Mavig), Vivosight (Michelson)	Microscopie confocale, Samba, (Bssa Nova technologies), Visioscan (C+K), Videomicroscope (Hirox), Dermascope (Dino-lite)
	Stratum corneum protein content	SquameScan (Heiland)
	Cutaneous absorption and thickness	Sonde Raman (Horiba Jobin), Vivascope (Mavig), Vivosight (Michelson)
	Softness	Frictiometer (C+K), Tribologie (Ecole Centrale)
Indirect	Epidermal Renewal	Quanti Squame
	Trans-epidermal water loss	Aquaflux (Biox) Vapometer (Delfin), Tewameter (C+K), Dermalab- TEWL (Cortex)
	Skin conductance	Corneometer, MoistureMap (C+K), Moisturemeter D (Delfin), Epsilon (Biox)
	Tissue oxygenation	Periflux (Perimed)
	Black head removal		TiVi80 (Wheelsbridge), Visa CR (Canfield), Videomicroscope (Hirox), Dermascope (Dino-lite)
	Skin gloss	Goniolux (Orion), Skin GlossyMeter (C+K) SkinGloss Meter (Delfin)

Everyone will find a representation of assessing exfoliating effect, whether the evaluation is direct or indirect. The choice of the method and the device will depend on:

• The level of requirement of the substance
• If the person responsible for the assessment or the formulator is waiting for a screening of formulas, marketing results with photos or data to complete the regulatory product file?

 

QuantiSquame

QuantiSquame is the most classical and direct method.

• It is easy and quick.
• A software analyzes the size and the number of the collected squames previously collected using a sticky patch.
• The Squame is positioned on a black surface with a uniform lightening.
• The light is diffracted and reflected by the presence of epidermal material collected. The whiteness of the image is proportional to the thickness of the sampled layers.
• The software calculates the occupied surface and gives desquamation index.

SquameScan : Analysis of Protein

The SquameScan – analysis of protein is the most innovative and new method of all.

• The corneocytes are collected with a Squame from the epidermis directly on the subject.
• The protein of the sample is determined by measurement of the optical absorption of D-dander at 850nm (light I – R).
• The value is given in percentage and is converted into protein by using a transfer function.
• The coefficients “a” and “b” are determined for each study comparing optic absorption to the former method of colorimetry.

Tomography or Raman Microscopy : High Tech & Visual Method

• Tomography or Raman microscopy give direct live images of the corneocytes, so, are considered high tech methods.
• The images of the surface of the skin surface are quite incredible.
• It is like a possible non-invasive biopsy which penetrates skin at the cellular level structure.

 

Indirect Methods

Indirect methods can also be interesting when coupled with a direct method.
Measurement of the trans-epidermal water loss (TEWL) will demonstrate that the skin is cleaned but not damaged.
The several evaporimeters used by the CRO’s are designed with a closed or open room technology. They measure the flow of water vapor including TEWL and the water lost from the skin surface.
Moreover, the homogeneity of the skin complexion can be a measure to evaluate the immediate effect of an exfoliating product. For example, the GonioLux allows measuring the intensity of light reflected by the face in all directions of space, simultaneously and quickly.
Finally, the motive of exfoliating devices or products is also to:

• Prepare the skin to receive the application of another product and
• Optimize the effect of the hydrating, anti-aging or slimming skincare.

Freed from these dead cells, skin facilitates the absorption of actives and the development of their efficacy.