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Ethnic skin types : are there differences in skin structure and function ? / Anthony Vincent Rawlings in IFSCC MAGAZINE, Vol. 9, N° 1 (01-02-03/2006)

[article]  inIFSCC MAGAZINE > Vol. 9, N° 1 (01-02-03/2006) . - p. 3-13 Titre : Ethnic skin types : are there differences in skin structure and function ? Type de document : texte imprimé Auteurs : Anthony Vincent Rawlings, Auteur Année de publication : 2006 Article en page(s) : p. 3-13 Note générale : Bibliogr. Langues : Anglais (eng) Tags : Ethnique  Racial  Biophysique  Epiderme  Derme Index. décimale : 668.5 Parfums et cosmétiques Résumé : People of skin of colour comprise the majority of the world's population and Asian subjects comprise more than half of the total population of the earth. Even so, the literature on the characteristics of the subjects with skin of colour is limited. Several groups over the past decades have attempted to decipher the underlying differences in skin structure and function in different ethnic skin types. However, most of these studies have been of small scale and in some studies interindividual differences in skin quality overwhelm any racial differences. There has been a recent call for more studies to address genetic together with phenotypic differences among different racial groups and in this respect several large-scale studies have been conducted recently. The most obvious ethnic skin difference relates to skin colour which is dominated by the presence of melanin. The photoprotection derived from this polymer influences the rate of the skin aging changes between the different racial groups. However, all racial groups are eventually subjected to the photoaging process. Generally Caucasians have an earlier onset and greater skin wrinkling and sagging signs than other skin types and in general increased pigmentary problems are seen in skin of colour although one large study reported that East Asians living in the U.S.A. had the least pigment spots. Induction of a hyperpigmentary response is thought to be through signaling by the protease-activated receptor-2 which together with its activating protease is increased in the epidermis of subjects with skin of colour. Changes in skin biophysical properties with age demonstrate that the more darkly pigmented subjects retaining younger skin properties compared with the more lightly pigmented groups. However, despite having a more compact stratum corneum (SC) there are conflicting reports on barrier function in these subjects. Nevertheless, upon a chemical or mechanical challenge the SC barrier function is reported to be stronger in subjects with darker skin despite having the reported lowest ceramide levels. One has to remember that barrier function relates to the total architecture of the SC and not just its lipid levels. Asian skin is reported to possess a similar basal transepidermal water loss (TEWL) to Caucasian skin and similar ceramide levels but upon mechanical challenge it has the weakest barrier function. Differences in intercellular cohesion are obviously apparent. In contrast reduced SC natural moisturizing factor levels have been reported compared with Caucasian and African American skin. These differences will contribute to differences in desquamation but few data are available. One recent study has shown reduced epidermal Cathepsin L2 levels in darker skin types which if also occurs in the SC could contribute to the known skin ashing problems these subjects experience. In very general terms as the desquamatory enzymes are extruded with the lamellar granules subjects with lowered SC lipid levels are expected to have lowered desquamatory enzyme levels. Increased pores size, sebum secretion and skin surface microflora occur in Negroid subjects. Equally increased mast cell granule size occurs in these subjects. The frequency of skin sensitivity is quite similar across different racial groups but the stimuli for its induction shows subtle differences. Nevertheless, several studies indicate that Asian skin maybe more sensitive to exogenous chemicals probably due to a thinner SC and higher eccrine gland density. In conclusion, we know more of the biophysical and somatosensory characteristics of ethnic skin types but clearly, there is still more to learn and especially about the inherent underlying biological differences in ethnic skin types. Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=10510 [article]

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Formulating for fast efficacy : influence of liquid crystalline emulsion structure on the skin delivery of active ingredients / Johann W. Wiechers in IFSCC MAGAZINE, Vol. 9, N° 1 (01-02-03/2006)

[article]  inIFSCC MAGAZINE > Vol. 9, N° 1 (01-02-03/2006) . - p. 15-21 Titre : Formulating for fast efficacy : influence of liquid crystalline emulsion structure on the skin delivery of active ingredients Type de document : texte imprimé Auteurs : Johann W. Wiechers, Auteur ; Caroline Kelly, Auteur ; T. G. Blease, Auteur ; J. Chris Dederen, Auteur Année de publication : 2006 Article en page(s) : p. 15-21 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Absorption cutanée Cosmétiques Formulation (Génie chimique) Tags : 'Perfectionnement  de  la  pénétration  peau'  'Cristaux  liquides'  Emulsions  'Pénétration  'Ingrédients  actifs'  'Acide  octadécénédioique'  Propagermanium Index. décimale : 668.5 Parfums et cosmétiques Résumé : In a previous publication, we described how the extent of skin delivery of an active ingredient can be optimized in a cosmetic formulation by the choice of a primary and secondary emollient. This paper describes our initial attempts to explain the influence of the emulsifier system on the dermal delivery of an active ingredient. Some of the emulsifiers studied in this investigation induced liquid crystal formation in the formulations and were found to interact in two different ways. On the one hand, they prevented the evaporation of water from the formulation when applied on the skin and in doing so prolonged the delivery phase of water-soluble active ingredients as only solubilized molecules penetrate the skin at reasonable rates. On the other hand, when combined with lipophilic active ingredients, the location to which the active ingredient is delivered was changed. This can be explained by a possible interaction of these emulsifiers with the skin lipid bilayers. These are present in an orthorhombic, an hexagonal and a liquid packing, which co-exist simultaneously and are characterized by a relatively low, an intermediate and a high permeability, respectively. The results obtained in this study suggest that the use of these liquid crystal formation inducing surfactant systems favors the presence of the more permeable packing states. In a given time, an active ingredient will therefore penetrate deeper into skin with emulsifier systems that induce liquid crystal formation than with systems that do not. It is therefore suggested that such emulsifier systems be used when fast delivery of a lipophilic active ingredient or more delivery of a hydrophilic active ingredient is required, and non-liquid crystalline systems if slower or less delivery is required. The use of liquid crystalline emulsifier systems therefore allows cosmetic formulators to regulate the extent (hydrophilic active ingredients) or speed (lipophilic active ingredients) of active ingredient delivery and thus to formulate for fast efficacy. Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=10511 [article]

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Resolving the conflict of a simultaneously highly moisturizing and occlusive emulsion film / Yuji Sakai in IFSCC MAGAZINE, Vol. 9, N° 1 (01-02-03/2006)

[article]  inIFSCC MAGAZINE > Vol. 9, N° 1 (01-02-03/2006) . - p. 23-28 Titre : Resolving the conflict of a simultaneously highly moisturizing and occlusive emulsion film Type de document : texte imprimé Auteurs : Yuji Sakai, Auteur ; Masashi Suzuki, Auteur ; Yasuhiro Ohara, Auteur ; Shinya Okabe, Auteur Année de publication : 2006 Article en page(s) : p. 23-28 Note générale : Bibliogr. Langues : Anglais (eng) Tags : 'Film  émulsion'  'Stratum  corneum'  'Surfactant  polyglycérine-type  '  'Fonction  hydratante'  occlusive'  'Microscope  laser' Index. décimale : 668.5 Parfums et cosmétiques Résumé : Two basic functions of emulsion-based cosmetic products are moisturization and occlusion, which are markedly affected by the ratio of hydrophilic to lipophilic parts in the emulsions. However, due to their conflicting requirements, it is difficult to simultaneously improve both functions. Therefore, we developed new emulsion that has simultaneously higher moisturizing and occlusive functions than those of polyoxyethelene-type emulsions, by using polyglycerin-type surfactants, acetyl alcohol, polyglycerin-13-polyoxybutylene-14-stearyl ether and the D-phase emulsification method, because of dispersing a large quantity of water into the lipophilic part of the applied emulsion film and of strengthening the hydrophilic part of the emulsion film. We confirmed through microscopic study with a laser microscope that in polyoxyethelene-type emulsions, droplets disappear quickly after the film is formed and dried, whereas in our experimental emulsions, the droplets’ shape is evenly retained. Furthermore, after 1 month of continuous use, stratum corneum removal and corneocyte arrangement also improved significantly. Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=10522 [article]

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Fluorescence and scanning electron microscopic characterization of cuticle erosion in human hair / Sigrid B. Ruetsch in IFSCC MAGAZINE, Vol. 9, N° 1 (01-02-03/2006)

[article]  inIFSCC MAGAZINE > Vol. 9, N° 1 (01-02-03/2006) . - p. 29-35 Titre : Fluorescence and scanning electron microscopic characterization of cuticle erosion in human hair Type de document : texte imprimé Auteurs : Sigrid B. Ruetsch, Auteur ; Yash K. Kamath, Auteur Année de publication : 2006 Article en page(s) : p. 29-35 Langues : Anglais (eng) Catégories : Caractérisation Cheveux -- Détérioration Cuticule -- Détérioration Fluorimétrie Microscopie électronique à balayage Tags : 'Cheveu'  'Exposition  environnementale'  au  toilettage  'Usure  du  cuticule'  'Caractéristiques  phénomène  de  dommage  cheveu'  'Microfluorométrie  SEM' Index. décimale : 668.5 Parfums et cosmétiques Résumé : Environmental and natural grooming damage of hair were investigated by the microfluorometric method using Rhodamine B as the fluorescent tracer. An increase in fluorescence intensity of tracer-tagged hair as we moved from the root to middle section and trip end is indicative of weathering and progressive mechanical damage. The locus of Rhodamine B penetration and interaction occurs at the scale edge in the root end, changing to the scale face and scale edge in the middle section, and finally to the cortical cell surfaces and the intercellular cement at the tip end in long hair. The resulting increase in fluorescence emission intensity is indicative of progressive damage to the cuticular structure, ultimately resulting in the loss of the cuticular sheath. Scanning electron microscopic observations show detailed features of progressive cuticle erosion and abltion. Characteristic changes in the physical nature and shape of the cuticle cell compared to its appearance as it emerged from the follicle are indicative of environmental and mechanical damage inflicted upon hair. Change of the smoothly contoured scale edge to its jagged shape, frequent appearance of "failed endocuticular material" left behind after the inextensible A-layer and exocuticle have been chipped away, and "tear lines" or "seams", which are the loci where the surface cuticle cells were orinally attached, are indicative of progressive cuticle erosion. Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=10535 [article]

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How skincare ingredient concentrations can modulate the effect of polyols and oils on skin moisturization and skin surface roughness / G. W. Nam in IFSCC MAGAZINE, Vol. 9, N° 1 (01-02-03/2006)

[article]  inIFSCC MAGAZINE > Vol. 9, N° 1 (01-02-03/2006) . - p. 37-41 Titre : How skincare ingredient concentrations can modulate the effect of polyols and oils on skin moisturization and skin surface roughness Type de document : texte imprimé Auteurs : G. W. Nam, Auteur ; S. H. Kim, Auteur ; Eun Joo Kim, Auteur ; J. H. Kim, Auteur ; Byeong Gun Chae, Auteur ; Hae Kwang Lee, Auteur ; S. J. Moon, Auteur ; Hak-Hee kang, Auteur ; Ih Seop Chang, Auteur Année de publication : 2006 Article en page(s) : p. 37-41 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Cosmétiques Formulation (Génie chimique) Huiles et graisses Peau -- Biopsie Peau -- Physiologie Peau -- Soins et hygiène Polyols Rugosité Index. décimale : 668.5 Parfums et cosmétiques Résumé : The aim of this study was to evaluate the influence of different skincare ingredient concentrations on the effect of polyols and oils on human skin moisturization and skin surface roughness. Polyols and oils are essential ingredients in a skin care formulation, but it is still not understood how their concentrations affect their efficacy and sensory properties on human skin. We studied various concentrations of ingredients from cosmetics companies using noninvasive methods. The polyols consisted of glycein and butylene glycol (BG) in a ratio of 1:1, and the oils consisted of equal parts of hydrogenated polydecene, cetyl ethylhexanoate and pentaerythrityl tetraethylhexanoate. All compounds were tested in O/W emulsions in concentrations ranging from 0-27% for polyols and from 0-35% for oils. We investigated the effect on water content and stratum corneum roughness on forearm skin after application of the compounds. The skin water content was determined by skin capacitance measurements and the skin surface roughness by visual scoring of skin surface biopsies in the scanning electron microcrographs. The water content of the skin correlated highly with the polyol (up to 20 %) and oil (up to 12 %) concentrations, respectively. Two hours after application the correlation coefficients were 0.971 and 0.985, respectively (p<0.01). Skin surface roughness not only showed a strong a ratio of 2.5 to 1 (polyols and oils). Further studies will be conducted with other ingredients such as surfactants, lipids and aqueous materials, and with other methods for noninvasive measurement. Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=10536 [article]

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