Age‐related changes in skin barrier function – Quantitative evaluation of 150 female subjects

The protection against water loss and the prevention of substances and bacteria penetrating into the body rank as the most important functions of the skin. This so‐called ‘skin barrier function’ is the natural frontier between the inner organism and the environment, and is primarily formed by the epidermis. An impairment of the skin barrier function is often found in diseased and damaged skin. An influence of ageing on skin barrier function is widely accepted, but has not been conclusively evaluated yet. Therefore, the aim of this clinical study was to assess the potential influence of ageing on skin barrier function, including transepidermal water loss (TEWL), stratum corneum hydration, sebum content and pH value. One hundred and fifty healthy women aged 18–80, divided into five age groups with 30 subjects each, were evaluated in this study. TEWL, hydration level, sebum secretion and pH value of hydro‐lipid acid film were measured with worldwide acknowledged biophysical measuring methods at cheek, neck, décolleté, volar forearm and dorsum of hand. Whereas TEWL and stratum corneum hydration showed only very low correlation with subject's age, the sebum production decreased significantly with age, resulting in the lowest skin surface lipids levels measured in subjects older than 70 years. The highest skin surface pH was measured in subjects between 50 and 60 years, whereas the eldest age group had the lowest mean pH. The dorsum of the hand was the location with the highest TEWL and lowest stratum corneum hydration in all age groups. The results show that only some parameters related to skin barrier function are influenced by ageing. Whereas sebum production decreases significantly over lifetime and skin surface pH is significantly increased in menopausal woman, TEWL and stratum corneum hydration show only minor variations with ageing.     

Enhanced efficacy and sensory properties of an anti‐dandruff shampoo containing zinc pyrithione and climbazole

Dandruff is a common complaint and is suffered by as much as half of the population at some time post puberty. The condition is characterized by the presence of flakes on the scalp and in the hair, and is often accompanied by itch. The most common treatment for dandruff is the use of shampoo formulations that contain fungistatic agents such as zinc pyrithione (ZPT) and octopirox. Whilst most antidandruff shampoos are effective in resolving the symptoms of dandruff these shampoos can often result in hair condition that is less than acceptable to consumers which can lead to a tendency for them to revert to use of a non‐antidandruff shampoo. This can result in a rapid return of dandruff symptoms. The aim of this investigation was to study the impact of using a combination of antidandruff actives and silicones on the resolution of dandruff and to deliver superior sensory properties to the hair. We have demonstrated that shampoo containing the dual active system of ZPT/Climbazole deposits both active agents onto a model skin surface (VitroSkin) and reduces Malassezia furfur regrowth in vitro. Clinical evaluation of the dual active shampoo demonstrated superior efficacy and retained superiority during a regression phase where all subjects reverted to using a non‐antidandruff shampoo. We have also demonstrated that it is possible to deposit silicone materials from antidandruff shampoo uniformly over both virgin and damaged hair fibres that results in smoother hair fibres (as evidenced by reduced dry friction). This combination of antidandruff agents and conditioning silicones delivered from a shampoo provides subjects with superior antidandruff efficacy and desired end sensory benefits ensuring compliance and longer term dandruff removal.     

The effect of hair care products on dandruff

Although the role of micro-organisms located on the surface of the scalp is disputed by some authors, lipolytic organisms within the hair follicle may still be implicated in the causation of dandruff. Scale formation appears to be an adaptive response to threshold scalp irritation, taking the form of minimal parakeratosis possibly induced by products of lipolysis permeating thin regions of the horny layer. No single pathogen is yet clearly identifiable but effective anti-dandruff compounds display good antimicrobial activity against the typical lipolytic scalp microflora; this activity is retained in the presence of sebum and a feature of the most efficacious anti-dandruff agents is their good substantivity to the epidermal horny layer.
L'action des produits capillaires sur les pellicules     

Hair and nail water‐holding capability measurements by using condenser‐TEWL method

We have developed a new method for studying human hair and nail water‐holding capabilities by using the condenser‐chamber trans‐epidermal water loss (TEWL) method. Healthy hair and nail always contain certain amount of water, and they will lose this water to the environment naturally through evaporations. We monitored this desorption process by continuously measuring the water vapour flux density from hair and nail using the condenser‐TEWL method, which is a condenser‐based closed‐chamber TEWL technology that is particularly suitable for this kind of measurements. We have also develop mathematical models for modelling the hair and nail desorption process. By fitting the normalized hair and nail desorption data with the mathematical models, we can get the water diffusion coefficient information, which can then be related to the water‐holding capabilities of the hair and nail samples.     

Effect of cationic charge and hydrophobic index of cellulose‐based polymers on the semipermanent dyestuff process for hair

In this work, the effects of a new class of polymers generally used in hair and skin cleansing products, the SoftCAT (SofCAT SL and SoftCAT SX), on the dye uptake on the hair fibre and the fading effects has been studied. These polymers, based on quaternary ammonium salts of hydroxyethylcellulose, are cationic products that differ in viscosity, hydrophobic substitution index (HS) and/or cationic substitution (CS, % N). UV–Vis spectroscopy has been used to analyse the extracted dyes from the hair cuticle and the cortex. The results indicate that the presence of polymers in the dye bath improve both the quality of the dyeing process and the anti‐fading effect during the washing cycles. This phenomenon is postulated to be attributable to the polymers hydrophobically bonding with the dyes and so facilitating their increased penetration into the hair.     

Location‐related differences in structure and function of the stratum corneum with special emphasis on those of the facial skin

Between the two different kinds of the skin covering the body, the glabrous skin is found only on the palmo‐plantar surface because of its rather simple function to protect the underlying living tissue with its remarkably thick stratum corneum (SC) from strong external force and friction. Thus, its barrier function is extremely poor. In contrast, the hair‐bearing skin covers almost all over the body surface regardless of the presence of long hair or vellus hair. In regard to its SC, many dermatologists and skin scientists think that it is too thin to show any site‐specific differences, because the SC is just present as an efficient barrier membrane to protect our body from desiccation as well as against the invasion by external injurious agents. However, there are remarkable regional differences not only in the living skin tissue but also even in such thin SC reflecting the function of each anatomical location. These differences in the SC have been mostly disclosed with the advent of non‐invasive biophysical instruments, particularly the one that enables us to measure transepidermal water loss (TEWL), the parameter of the SC barrier function, and the one that evaluates the hydration state of the skin surface, the parameter of the water‐holding capacity of the SC that brings about softness and smoothness to the skin surface. These in vivo instrumental measurements of the SC have disclosed the presence of remarkable differences in the functional properties of the SC particularly between the face and other portions of the body. The SC of the facial skin is thinner, being composed of smaller layers of corneocytes than that of the trunk and limbs. It shows unique functional characteristics to provide hydrated skin surface but relatively poor barrier function, which is similar to that observed in retinoid‐treated skin or to that of fresh scar or keloidal scars. Moreover, there even exist unexpected, site‐dependent differences in the SC of the facial skin such as the forehead, eyelid, cheek, nose and perioral regions, although each location occupies only a small area. Between these locations, the cheek shows the lowest TEWL in contrast to the perioral region that reveals the highest one. Moreover, these features are not static but change with age particularly between children and adults and maybe also between genders. Among various facial locations, the eyelid skin is distinct from others because its SC is associated with poor skin surface lipids and a thin SC cell layer composed of large corneocytes that brings about high surface hydration state but poor barrier function, whereas the vermillion borders of the lips that are covered by an exposed part of the oral mucosa exhibit remarkably poor barrier function and low hydration state. Future studies aiming at the establishment of the functional mapping in each facial region and in other body regions will shed light on more delicate site‐dependent differences, which will provide us important information in planning the strategy to start so called tailor‐made skin care for each location of the body.     

In vivo barrier challenge and long‐term recovery in human facial skin

Recently, we developed a biophysical approach to characterize in vivo facial cheek skin as a function of stratum corneum (SC) depth, barrier function and during a 24‐h recovery period. The current study extends this work and characterizes the human facial cheek after barrier challenge and, for the first time, facial SC barrier recovery over a 4‐week period. Changes in the corneocyte size over the 4‐week recovery period, and correlations with changes in Trans‐Epidermal Water Loss (TEWL) were monitored. This approach allows complete characterization of SC barrier function after a full biological regeneration of the SC barrier following tape stripping. The structural and compositional changes in facial cheek were investigated using Attenuated Total Reflectance‐Fourier Transform Infra Red (ATR‐FTIR) spectroscopy, tape stripping, TEWL measurements and image analysis combined with optical microscopy to characterize the SC depth profile during the tape stripping stress and over 4‐week recovery period. TEWL increased significantly from baseline after sequential tape stripping. Corneocyte size decreased with successive tape stripping. An inverse direct correlation was determined between TEWL and corneocyte surface area. After 4 weeks, the corneocyte size and TEWL for the facial cheek recovered 100% from the tape stripping procedure. The in vivo ATR‐FTIR data demonstrated that lipid and sebum components on the surface of the facial cheek SC recovered within 24 h post tape stripping, whereas protein (Amide II) and water components recovered after 1 week.     

发用类、肤用清洁类化妆品的急性皮肤和眼刺激损害特点

分析发用类、肤用清洁类化妆品的急性皮肤刺激和急性眼刺激损害特点,了解其卫生安全状况。于2012年采用《化妆品卫生规范》(2007年版)中的急性皮肤刺激性实验和急性眼刺激性实验对发用类、肤用清洁类共计158种化妆品样品进行测试。两类受试化妆品显示出不同程度的急性皮肤刺激性和急性眼刺激性损害效应。发用类化妆品在实验中基本无皮肤刺激性损伤;肤用清洁类化妆品在实验中有少量的皮肤刺激性损伤,但大都为轻刺激性(31.0%),只有个别(3.8%)出现了皮肤红斑水肿的中刺激性损伤。发用类、肤用清洁类化妆品在急性眼刺激性实验中检出一定比例具有微刺激性及以上刺激性的样品,但引起的眼损伤都能够在观察期限内恢复。本次调查的所有化妆品中,洁面类、洗发类化妆品普遍具有急性眼刺激性和急性皮肤刺激性损害,需加强对化妆品的监督管理,进一步提升化妆品卫生安全水平,保障化妆品使用安全。     

Facial skin mapping: from single point bio‐instrumental evaluation to continuous visualization of skin hydration,barrier function,skin surface pH,and sebum in different ethnic skin types

Dry skin is one of the most important concerns of consumers worldwide. Despite huge efforts over several decades, the personal care industry still does not offer a perfect solution to satisfy the unmet needs of consumers for moisturising treatments in different ethnic groups. The paucity of data for the underlying cellular and biochemical problems in, and the effects of moisturisers on photodamaged facial skin may partly explain this. Mainly, single point measurements are used to understand the effects of products on skin physiology even on surrogate skin sites such as the non‐photodamaged volar forearm. Some groups have developed discontinuous facial maps of skin biophysical properties, however, in 2014 a continuous facial analysis of bio‐instrumental evaluations was developed using a heat map approach. These maps enabled a continuous visualization of features that not only revealed an unexpected complexity of facial skin but also indicated that use of surrogate skin sites for facial skin is inappropriate. We have demonstrated that remarkable gradients of skin hydration, TEWL, skin surface pH and sebum exist within short distances across the face and the gradients are distinctive among different ethnic groups. In addition, these studies have demonstrated that darkly‐pigmented individuals do not necessarily have a better skin barrier function than their less‐pigmented counterparts and that Caucasians have a lower facial skin surface pH compared with more pigmented subjects. Overall, there are no correlations between capacitance, TEWL and skin surface pH including individual topology angle values. Novel 3D camera approaches have also been used to facilitate a more precise assignment of measurement sites and visualisation. The 3D facial colour mappings illustrated precisely the local moisturising effects of a moisturising cream. There were subtle ethnic differences in efficacy that may be related to underlying skin biochemistry and/or ethnic differences in product application. A placebo‐controlled study using conductance measurements in Chinese subjects is also reported. Finally, a new whole face statistical approach has been taken to prove differences in skin parameters but also of moisturiser treatment that adds further to our understanding of the ethnic differences in skin physiology and product application. This paper reviews the background of the development and application of this methodology.     

The use of transepidermal water loss to measure and predict the irritation response to surfactants

The ability of baseline transepidermal water loss (TEWL) measurements to predict the response of healthy subjects to a standard soap chamber irritation insult was evaluated. Chambers containing surfactant solutions were applied to the forearms of normal volunteers for five consecutive days. TEWL was measured using a Servo Med Evaporimeter. TEWL measurements were made prior to the first application of the chambers and following the removal of the second set of chambers (the afternoon of Day 1). The correlation between the TEWL values obtained on Day 1 and the subjective evaluation of irritation resulting from the application of two different toilet soaps was statistically significant. This result indicates that damage to the skin is reflected by an increase in TEWL. Interestingly, there was also a statistically significant correlation between TEWL values obtained on the untreated skin at Time 0 and the five-day average irritation score for these two cleansing products. The results of this study indicate that a high baseline TEWL value may be predictive of a high susceptibility to soap irritation as measured by the chamber test.
Le role des pertes en eau transepidermique pour mesurer et prevoir l'irritation due aux tensio-actifs     

Caffeine improves barrier function in male skin

The influence of androgens, especially testosterone and its effector dihydrotestosterone, results in a constitutive disadvantage for male skin, e.g. reduced viability of hair at the scalp and reduced epidermal permeability barrier repair capacity. Dihydrotestosterone can act, among others, as an adenyl cyclase inhibitor. Caffeine on the other hand is an inexpensive and (in regular doses) harmless substance used in various cosmetic products, which can act as a phosphodiesterase inhibitor. To prove the hypothesis that caffeine as a phosphodiesterase inhibitor is able to override testosterone-induced effects on barrier function, we performed a double-blind placebo controlled study with healthy volunteers. In this study, 0.5% caffeine in a hydroxyethylcellulose gel preparation (HEC) was applied on one forearm, HEC without caffeine on the other forearm of male and female volunteers for 7 days and transepidermal water loss (TEWL) was measured before and at the end of the treatment period. Basal TEWL did not differ significantly between male and female subjects but the application of caffeine significantly reduced TEWL in male skin compared with female skin. We conclude that caffeine is beneficial for barrier function in male skin.     

Effect of reaction pH and CuSO4 addition on the formation of catechinone due to oxidation of (+)‐catechin

A novel hair dyeing technique being milder and safer for a human body is desired. The oxidation product of (+)‐catechin, catechinone, was invented as a safer dyestuff for hair colouring under such the situation. The preparation of catechinone by a chemical oxidation is a practical way and the objective of the study is clarify the effect of the solution pH and in the presence or absence of Cu²⁺ on the formation rate and yield of catechinone in order to improve the efficiency of the dye formation. The catechinone formation was monitored by ultraviolet‐visible spectroscopy. Catechinone was prepared chemically from (+)‐catechin in aqueous solution with O₂ gas introduced over a pH range of 7.1–11.7. The rate and amount of the dye formation increase with increasing pH. Dissociation of the hydroxyl group of the catechol part of (+)‐catechin is significant for the oxidation of (+)‐catechin and promotes the dye production. This is because the deprotonated (+)‐catechin has a higher reactivity with O₂. The production of catechinone is accelerated by the addition of CuSO₄ and the production rate reaches the maximum at pH = 8.8. (+)‐Catechin ‐ Cu²⁺ complexes are formed and the formation promotes the oxidation of the catechol part of (+)‐catechin at pH ≤ 8.8. On the other hand, the complex becomes too stable to proceed for the oxidation reaction at pH > 8.8.     

Capacitance, transepidermal water loss and causal level of sebum in healthy subjects in relation to site, sex and age

To determine normal levels of transepidermal water loss (TEWL), capacitance and sebum according to different sex and age groups, 93 healthy subjects were studied at 14 different anatomical locations with three different instruments: the Evaporimeter EP 1, the Corneometer CM 820, and the Sebumeter SM 810, evaluating respectively the transepidermal water loss, the capacitance and the causal level of sebum. Differences depending on the anatomical site were noticed. Unlike the capacitance, the transepidermal water loss and the causal level of sebum significantly decreased according to age. Furthermore, in some sites, male subjects showed a significantly higher transepidermal water loss than females, while hydration of the horny layer expressed by the capacitance showed an opposite trend. Correlations between the above-mentioned skin parameters were calculated: a positive correlation between TEWL and hydration was observed only at plantar and palmar areas.     

Effect of São Pedro do Sul thermal water on skin irritation

Many mineral waters are known for centuries for treating dermatological diseases but there is little scientific evaluation of the effects of these waters in skin. A total of 17 healthy Caucasian volunteers, including men and women, were enrolled in this study. Two skin sites were marked on each volunteer forearm and irritated with sodium lauryl sulphate at 2% (w/v) kept under occlusion for 24 h with Finn chambers. Afterwards, purified water or São Pedro do Sul (SPS) thermal water were applied to the irritated skin sites, and kept under occlusion for 48 h also with Finn chambers. Transepidermal water loss (TEWL) was used as a measure of the skin barrier function to evaluate the potential anti‐irritant effect of the thermal water on skin. Statistically significant differences in the mean TEWL variations were observed for the skin treated with SPS thermal water and with purified water (P = 0.036). The thermal water reduced the degree to which the skin barrier was disrupted compared with purified water alone in 82.4% of the volunteers. The SPS thermal water is anti‐irritant and, therefore, can be helpful to relieve skin irritation and in cosmetic formulations to improve the tolerability of the products.     

A review of shampoo surfactant technology: consumer benefits,raw materials and recent developments

Surfactants form the core of all shampoo formulations, and contribute to a wide range of different benefits, including cleansing, foaming, rheology control, skin mildness and the deposition of benefit agents to the hair and scalp. The purpose of this review was to assist the design of effective, modern, shampoo surfactant technologies. The mechanisms through which surfactants help deliver their effects are presented, along with the appraisal techniques through which surfactant options can be tested and screened for product development. The steps that should be taken to select the most appropriate blend of surfactants are described, and useful information on the most widely used surfactants is provided. The review concludes with an examination of recent developments in ‘greener’ surfactants, ‘sulphate‐free’ technologies and structured liquid phases for novel sensory properties and for suspending benefit agents.     

Dandruff: infection or not?

The presence of apparently normal corneocytes as well as parakeratotic material in dandruff scales suggests that atypical keratinization in the scalp epidermis has not been of long duration. Abundance of hair fat on the scalp after puberty, colonization by fat-splitting micro-organisms (notably yeasts of the genus Pityrosporum) and transitory upsurges of epidermal mitosis in response to fatty acids produced by lipolysis of sebum triglycerides within the hair follicles, especially those in the anagen phase, seem likely to be implicated in the generation of dandruff scaling. Antidandruff efficacy apparently calls not only for antifungal potency demonstrable in vitro but also for the ability, when incorporated in a suitable formulation, to reach the microflora within the hair follicles and to inhibit the metabolic activity of these microorganisms even in the presence of sebum. The in vivo demonstration of an alleged ‘anti-hyperproliferative'effect of an antidandruff compound has been described but probably has only coincidental relationship to its normal function in the control of dandruff, which seems more likely to depend on its antimicrobial properties. The available evidence thus tends to favour the view that the scalp microflora have a predominant role in the generation of dandruff. Pellicules: origine microbienne ou non microbienne?     

Human synthetic sebum formulation and stability under conditions of use and storage

The human skin surface and hair are generally coated with a thin film of liquid phase sebaceous lipids. This surface lipid film contributes to the cosmetic properties of the skin. Synthetic sebum has been used for studies on properties of skin and hair. However, there has been no standardized formulation of synthetic sebum and many of the synthetic sebum formulations that have been used do not closely resemble actual sebum. In this study, a formulation for a standardized and inexpensive synthetic sebum is proposed, and the chemical stability of this lipid mixture is demonstrated under conditions of use and storage. The proposed synthetic sebum consists of 17% fatty acid, 44.7% triglyceride, 25% wax monoester (jojoba oil) and 12.4% squalene. This lipid mixture takes up approximately 6% of its weight in water when equilibrated in an atmosphere saturated with water vapour. It is stable on exposure to the atmosphere at 32°C for at least 48 h, and it is also stable on storage at 4 or −20°C, either dry or in chloroform : methanol solution for at least 6 months. This synthetic sebum could be useful in studies on cosmetic properties of the skin surface or hair, on penetration of chemicals into the skin or in development of standardized tests of laundry detergent performance.     

The influence of alkane chain length on the skin irritation potential of 1,2-alkanediols

Several studies have reported that 1,2-alkanediols show increasing anti-microbial activity as their alkane chain length increases. However, there are no reports on the influence of alkane chain length on the skin irritation potential of 1,2-alkanediols. To investigate the influence of alkane chain length on the skin irritation potential of 1,2-alkanediols. The objective and subjective (sensory) skin irritation potentials of five 1,2-alkanediols - 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-octanediol and 1,2-decanediol - were evaluated. We also estimated percutaneous absorption by measuring in vitro skin penetration using a Franz diffusion cell system. Like anti-microbial activity, sensory irritation potential increased as alkane chain length increased, most likely due to increasing membrane interference and/or intrinsic toxicity of 1,2-alkanediols. 1,2-Hexanediol showed the lowest objective skin irritation potential, which increased when the alkane chain length decreased or increased. Furthermore, percutaneous absorption negatively correlated with the alkane chain length of 1,2-alkanediols. These results show that a lower skin absorption potential is not indicative of a low skin irritation potential. Our results suggest that the factors and processes involved in skin irritation potential are complex and that skin irritation potential is influenced by intrinsic toxicity and the potential for penetration or integration in the lipid bilayer.     

The influence of a cream containing 20% glycerin and its vehicle on skin barrier properties

Glycerin is widely used in cosmetics and well as in pharmaceutical formulations, mainly as humectant. In vitro studies have shown glycerin to prevent crystallization of stratum corneum model lipid mixture at low room humidity. Whether this may affect the skin barrier function during repeated application of glycerin in a cream base to normal skin is not known. Therefore, the influence of a cream containing 20% glycerin was compared with its placebo cream in a bilateral, double-blind study on 17 healthy volunteers. The effect was evaluated as influence on hydration with a corneometer and on skin barrier function. Skin barrier function was assessed as permeability to water with an evaporimeter (transepidermal water loss; TEWL) and as sensitivity to an irritating surfactant by measuring the biological response (measured as TEWL and skin blood flow). Ten days treatment of normal skin with 20% glycerin significantly increased skin corneometer values, indicating an increased hydration. However, our study failed to show an influence of glycerin on human skin, in terms of TEWL and skin sensitivity to SLS-induced irritation.     

On the effects of a plant extract of Orthosiphon stamineus on sebum‐related skin imperfections

Overproduction of sebum is very common and results in an undesirable oily, shiny complexion with enlarged pores. Sebum secretion is basically under the control of 5‐α reductase, and more particularly under that of type 1 isozyme. But it is also highly sensitive to environmental factors such as temperature, humidity and food. Moreover, in Asia, the edicts of a flawless facial skin turn oily skin into a major concern for Asian women. We identified Orthosiphon stamineus leaf extract as an interesting ingredient for reducing the oily appearance of skin thanks to its ability to reduce 5‐α reductase type 1 expression in normal human epidermal keratinocytes in vitro. This was confirmed ex vivo, where Orthosiphon stamineus leaf extract was shown to reduce 5‐α reductase activity as well as the production of squalene, one of the main components of sebum that was used as a tracer of sebum. To evaluate the efficacy of Orthosiphon stamineus leaf extract at reducing sebum‐related skin imperfections in vivo, we performed two different clinical studies, one in France on a panel of Caucasian volunteers and the other one in Thailand on a panel of Asian volunteers. Using instrumental techniques as well as clinical evaluation and self‐evaluation, we could highlight that an O/W cosmetic formula containing 2% of Orthosiphon stamineus leaf extract could visibly reduce the oily appearance of skin as well as the size of pores, thus leading to a significant improvement of complexion evenness and radiance. Overall, the results obtained were better than those observed with the same formula containing 1% of zinc gluconate, an ingredient frequently used in oily skin care products.