Examination of the effects of a moisturizer on facial barrier and hydration of three skin ethnicities using a novel mapping approach

Transcription

1 Examination of the effects of a moisturizer on facial barrier and hydration of three skin ethnicities using a novel mapping approach R Voegeli 1, P Seroul 2, LA Raaff 3, M Lategan 3, AV Rawlings 4, B Summers 3 1 DSM Nutritional Products Ltd., Switzerland 2 Newtone Technologies, Lyon, France 3 The Photobiology Laboratory, Sefako Makgatho University, Medunsa, South Africa 4 AVR Consulting Ltd., United Kingdom Objectives Research tells us that we are not completely meeting consumers needs for skin moisturization. As much as 70% of women can be affected with dryness on their faces which can vary with season and also facial location [1] [2] [3]. Recent work indicates that the use of single point measures on the face is not enough to describe the complexity of the moisturization needs of the face. Mapping procedures have been undertaken with a limited number of sites [4] [5] [6] but we recently demonstrated the immense complexity of the barrier and hydration properties of facial skin using 30 predefined sites on one side of the face of subjects of four different skin ethnicities [7]. The aim of this study was to evaluate the effect of a moisturizer on continuous facial color maps of transepidermal water loss (TEWL) and skin hydration. Materials and Methods Study population and study set up The study was a cross-sectional study and was approved from the School of Health Care Sciences Research and Ethics committee (SREC) together with the Medunsa Campus Research and Ethics Committee (MREC) and was conducted in accordance with the Declaration of Helsinki Principles. Written, informed consent was obtained from all participants before enrollment. In this study we determined the effect of a moisturizing cream on 36 healthy female subjects of three different skin ethnicities (Black Africans, Indians and Caucasians) over a period of four weeks. Each group consisted of twelve subjects each. In order to limit the biological variability of the subject groups young female volunteers (20-23 years old) without visual signs of photoaging were enrolled, all living in Pretoria, South Africa. The study was composed of a three day conditioning phase and a 28 day application phase. For the three day conditioning phase the subjects did not apply any dermatological or cosmetic products. In the application phase a moisturizing cream (Table I) was applied twice daily, once in the morning and once in the afternoon, under normal conditions of use. Table I: INCI list of ingredients of the test cream Aqua, Diisopropyl Sebacate, Glycerin, Niacinamide, C12-15 Alkyl Benzoate, Glyceryl Myristate, Butyl Methoxydibenzoylmethane, Polysilicone-15, Octocrylene, Potassium Cetyl Phosphate, Dicaprylyl Ether, Titanium Dioxide, Saccharide Isomerate, Dimethicone, Methyl Methacrylate Crosspolymer, Cetyl Alcohol, Phenoxyethanol, Citric Acid, Sodium Citrate, Ethylhexylglycerin, Xanthan Gum, Silica, Disodium EDTA, Parfum, BHT, Hydroxycitronellal, Hexyl Cinnamal, Butylphenyl Methylpropional, Limonene

2 In the morning, the face was cleansed with tepid water and in the afternoon with a standardized, mild facial cleanser. After cleansing, the face was carefully padded dry and not rubbed with a soft towel. Before conducting the bio-instrumental measurements, the skin was cleansed by gentle swabbing with a cotton pad soaked with distilled water of ambient temperature and allowed to dry for 20 minutes. Subjects were acclimatized for 30 minutes before any measurements and measurements were performed in a climate controlled room at a temperature of 21 ± 1 o C and 35 ± 10% relative humidity. The evaluations on day 28 were taken at least 12 hours after the last application of the moisturizing cream. Hydration and barrier function assessments SC capacitance was measured using a Corneometer CM825 (Courage & Khazaka, Colonge electronic, Germany) and basal TEWL using an Aquaflux AF200 (Biox Systems, London, UK) on 30 predefined sites on the left hand side of the face. All procedures were conducted following the published guidelines [8] [9] [10]. Skin capacitance was expressed as the mean value of three recordings, TEWL was measured once. Digital images were taken with the Visia-CR imaging system (Canfield, Fairfield, NJ, USA) from anterior, oblique and lateral view. In order to reduce an inter-individual variation of the measurements a template was used to ensure the same facial site was measured on each occasion (Table II and Figure 1). Table II: Description of facial sites measured Site # Description of site Site # Description of site 01 Forehead, central, upper 16 Nose, apex 02 Forehead, central, middle 17 Nasolabial sulcus, top 03 Forehead, central, lower 18 Cheek, middle, oblique 04 Forehead, middle left, upper 19 Cheek, middle, oblique/lateral 05 Forehead, middle left, middle 20 Cheek, middle, lateral 06 Forehead, middle left, lower 21 Philtrum 07 Forehead, left, middle 22 Nasolabial sulcus, midpoint 08 Forehead, left, lower 23 Cheek, lower, oblique 09 Eyelid 24 Cheek, lower, oblique/lateral 10 Forehead, outer, level with eyebrow 25 Cheek, lower, lateral 11 Nose, bridge 26 Chin, central 12 Under eye, inner corner 27 Jaw, anterior/oblique 13 Under eye, middle 28 Jaw, oblique 14 Outer eye canthus 29 Jaw, oblique/lateral 15 Cheek, lateral 30 Jaw, lateral

3 Figure 1: Anterior, oblique and lateral Visia-CR images of 30 predefined facial sites measured, shown on one selected subject. Color mapping of the bio-instrumental readings Each of the predefined sites was positioned on the Visia-CR images and X and Y coordinates were recorded. A 2D model was computed to link TEWL and capacitance data to the corresponding facial positions. Between each measuring sites, physiological values are interpolated using a thin plate spline transform. It allows to obtain a value for all pixels (X, Y) of the facial image. Two color maps were created to represent TEWL and capacitance. They generate color for each physiological value. The choice was made to represent good skin condition in deep blue and impaired skin condition in deep red. Limit skin condition is set to white color. It is set to 16 g m -2 h -1 for TEWL values and 40 AU for capacitance. Between these landmarks, colors are linearly interpolated in the CIELAB space. Finally, skin pixels on the Visia-CR images are segmented and, depending on their position, biophysical data are attached to them. The corresponding color is superimposed to the original value with a transparency level [11]. Statistics All data were collected in Microsoft Excel 2010 and checked for normality using the D Agostino and Pearson omnibus normality test. As all data was normally-distributed unpaired T-tests were used to compare each testing site. Results The moisturizer cream improved skin hydration and TEWL across many facial sites that were predetermined to be deficient in these essential stratum corneum properties. As in our previous study [7], the facial color maps of TEWL and hydration were considerably different among the three ethnic groups with the Caucasians have the lowest overall TEWL values and the Black Africans having the highest overall hydration values. The Indians had the highest TEWL but intermediary skin hydration values. Likewise, capacitance and TEWL gradients were observed within short

4 distances on the face. Four weeks after application of the moisturizer these facial gradients smoothed out on all three ethnic groups. However, certain zones of the face were improved markedly better than others. Discussion and Conclusion In an attempt to understand the complexity of facial moisturization several groups have performed a mapping analysis on five to six facial sites per half face [4] [5] [6]. Many differences in skin hydration and skin barrier properties have been observed in different parts of the face. We have built on this approach by comparing capacitance together with TEWL measurements on 30 predefined sites on one side of the face and decided to better visualize the data using a continuous color map of the values by interpolating between the measurement values. We believe that just measuring one half of the face in subjects with normal skin is valid as a good correlation of measurements of TEWL between both sides of the face has been reported by others [4] [12]. Also for the first time we decided to compare the measurements using this novel approach and to evaluate the effect of a moisturizer between three ethnic groups. The complexity of skin hydration and barrier properties of facial skin are revealed by the individual measurements on the 30 defined facial sites among the three ethnic groups but more particularly by the visualization of these results in continuous TEWL and capacitance maps. The lack of concordance between skin hydration and TEWL is clearly apparent. Equally, it is very obvious that big differences in TEWL and hydration could be observed among the three ethnic groups depending on the facial site chosen. Not only does our study highlight the complexity of the properties of facial skin regions and the need for very precise studies on facial skin properties among different ethnic groups, it also exposes the lack of comparative information that can be obtained from the testing of moisturizers on volar forearm skin. Perhaps this is one of the reasons why facial dry skin is still a major unmet consumer need. Nevertheless, the underlying biochemical differences in the stratum corneum in these facial locations between the different ethnic groups are not well understood. Our study approach is a first attempt to understand the effects of moisturizers on facial skin properties in different ethnic groups. In conclusion, although there are indications that measurements of TEWL and skin capacitance vary on the different parts on the face there is no previous literature on the complexity of facial TEWL and skin capacitance gradients in different ethnic groups. Our facial maps not only demonstrate the need for precise facial measurements and study designs but also that facial skin care application concepts for the different skin ethnicities need to consider facial anatomical locations. This study shows for the first time the need for a better understanding of the selective effects of moisturizers on facial skin properties and highlights the opportunity to improve particular zones of the face that require more efficacious treatments. This approach will go some way to meeting a major unmet consumer need - namely facial dryness.

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