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.     

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.     

Cream or foam in pedal skin care: towards the ideal vehicle for urea used against dry skin

The aim of this study was to evaluate different urea‐containing cosmetic preparations designed for foot care regarding skin occlusion. The primary aim was therefore to screen the short‐term transepidermal water loss (TEWL) as a parameter for skin barrier function and skin occlusion and to characterize the relative role of the vehicle, i.e. cream or foam in the context of cosmetics containing urea in the 2–10% range addressing the cosmetic products urea 2% cream (GEHWOL FUSSKRAFT blau), petrolatum containing cream (GEHWOL med Schrundensalbe), urea 10% cream (GEHWOL med Lipidro‐Crème), urea 10% foam (Allpresan Fuss Schaum) and vaseline (positive control) compared with an untreated area on the volar forearms of volunteers. Moreover, the short time (24 h) kinetics regarding the moisturizing effect of cream and foam formulations in diabetic patients were compared. The efficacy of a cream on reduction of skin thickness of hyperkeratotic skin in the heel region before and after a period of product application was also evaluated. In some of the trials, healthy individuals and in others, diabetic patients (type I and II) were enrolled. TEWL was determined before product application, as well as at given points of time thereafter. In this study, no excessive occlusion effects comparable with a blockage of the skin’s natural water evaporation could be observed for any of the test products. To the extent to be expected, this was found neither for the cream products nor for the foam product. Slightly lowered TEWL values after application of the 10% urea cream can be interpreted as a beneficial effect in terms of an improved barrier function. Regarding skin moisture, the urea‐containing cream formulation appeared equal or slightly superior to the foam formulation. The thickness of the horny layer was found reduced after application of 10 % urea‐containing cream. At present it looks as if cream vehicles would still be vehicles of choice in general, when it comes to the formulation of skin care preparations for not only dry skin but also in the context of pedal skin care.     

Effects of topical gluco-oligosaccharide and collagen tripeptide F in the treatment of sensitive atopic skin

Sensitive skin is a dermatological problem of increasing incidence in western countries and is sometimes associated with atopic condition and bacterial sovrainfection. The purpose of this study is to evaluate in a double blind, randomized, placebo controlled trial the efficacy of gluco-oligosaccharide and collagen tripeptide F in controlling the signs and symptoms of sensitive atopic skin. Forty female subjects (age, 30–59 years) affected by non-lesional atopic sensitive skin entered the study. Skin sensitivity was determined by a dermatologist on the basis of medical history, stinging test, dermatological examination and a questionnaire. A treatment with the test products (active and placebo) was carried out for 4 weeks. Measurements and clinical evaluation were carried out at baseline and at the end of the study. The following objective parameters investigated were bacterial count, skin pH and colour, transepidermal water loss (TEWL), stratum corneum hydration, skin roughness and mechanical properties. Clinical assessment included also a scoring system for dryness, desquamation, irritation, erythema and papules. Significant differences were found in the active treated group when compared with the placebo and in particular for instrumental parameters of roughness ( P  < 0.02), volume ( P  < 0.01), TEWL ( P  < 0.02), erythema ( P  < 0.0006) and clinical parameters of dryness, desquamation and irritation ( P  < 0.001). Moisturization levels and skin colour improved significantly in both the active and placebo groups. In conclusion, the study shows that the modulation of bacterial proliferation and normalization of skin barrier properties and stratum corneum moisturization can improve the symptoms of sensitive skin.     

Stratum corneum barrier integrity controls skin homeostasis

The stratum corneum water barrier controls structural and functional properties of both the epidermis and the dermis. Treatments which chronically disrupt the stratum corneum water barrier can induce changes similar to those seen with 'anti-aging' treatments such as (-Hydroxy acids (AHAs) and Retin Atrade mark. Barrier disruption via daily tape stripping increases epidermal and dermal thickness, superficial and integral skin firmness, and improves skin surface texture. Modest or transitory disruption did not produce such effects. Similar results were observed with topical application of AHAs, retinoids or mild irritants after about 4-6 weeks provided such treatments resulted in prolonged elevation in TEWL (trans-epidermal water loss). Treatments that did not chronically elevate TEWL could also produce positive cosmetic effects, but such effects were in general restricted to the skin surface or epidermis. Irritation, which was observed with some treatments, was not solely responsible for the positive effects observed.     

Systemic evening primrose oil improves the biophysical skin parameters of healthy adults

Biophysical skin parameters are indicators of age-related structural and functional changes in skin tissues. This randomized, double-blind, placebo-controlled study in healthy adults tested the effect of Efamol evening primrose oil [EPO, a gamma-linolenic acid (GLA) containing vegetable oil] on skin moisture, transepidermal water loss (TEWL), redness, firmness, elasticity, fatigue resistance and roughness. Efamol EPO was administered orally in soft gel capsules, 3 x 500 mg b.i.d. for 12 weeks. Measurements were taken at baseline and at weeks 4 and 12. The two treatment groups did not differ at baseline and at week 4. At week 12, however, all measured variables, with the exception of skin redness, were significantly different in the EPO group compared with placebo. Skin moisture, TEWL, elasticity, firmness, fatigue resistance and roughness had significantly improved by 12.9, 7.7, 4.7, 16.7, 14.2 and 21.7%, respectively. The two-sided levels of significance in favor of the EPO treatment ranged between 0.034 and 0.001. These findings lend further support to the notion that GLA is a conditionally essential fatty acid for the skin, i.e. it is unable to synthesize GLA, and therefore depends on preformed GLA for optimal structure and function.     

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.     

Five dimensions of cleansing: A holistic view on the facets and importance of skin cleansing

Cleansing is an important human ritual practised for hygiene, well-being and relaxation over centuries. As part of body care it is often taken for granted, yet its relevance cannot be underestimated. Although cleansing the skin may seem trivial to some, it is accepted, that this fundamental function of skin cleansing products is highly complex, diverse and crucial for a variety of reasons in the personal, public, healthcare and dermatological settings. Employing a comprehensive and strategic approach in viewing cleansing and its rituals, supports innovation, understanding and development. Apart from being a fundamental function, as far as we know, there is no comprehensive presentation of skin cleansing with all its effects besides ‘removing dirt’. To our knowledge, comprehensive analyses on the multi-dimensional facets of skin cleansing are either rare or not published. Against this background, we examine the importance of cleansing in terms of function, relevance and concepts. First, the key functions and efficacies of skin cleansing were investigated by literature research. Based on this survey, the functions were analysed, sorted and merged and a novel approach to skin cleansing ‘dimensions’ was developed. Herewith, we took into consideration the evolution of skin cleansing in terms of concept evolution, complexity and testing methods for cleansing products and their claims. Several multi-dimensional functions of skin cleansing were identified and then established into five skin cleansing dimensions, namely: hygienic and medical importance; socio-cultural and interpersonal relevance; mood, emotion and well-being; cosmetic and aesthetic function; corneobiological interactions. It became obvious, that these five dimensions with their corresponding 11 sub-dimensions, are influenced by each other throughout history by culture and society, technical progress, scientific knowledge and consumer trends. This article presents the enormous complexity of skin cleansing. Skin cleansing has evolved from basic care up to a highly complex and diverse cosmetic product category in terms of technology, efficacy and usage routine(s). In view of future challenges, such as the effects of climate and associated lifestyle changes, the development of skin cleansing will remain an exciting and important topic and thus will finally, again, further increase the complexity of skin cleansing itself.     

An oral nutraceutical containing antioxidants, minerals and glycosaminoglycans improves skin roughness and fine wrinkles

Various nutraceuticals (dietary supplements) are claimed to have cutaneous antiageing properties, however, there are a limited number of research studies supporting these claims. The objective of this research was to study the effectiveness of an oral nutraceutical containing antioxidants, minerals and glycosaminoglycans on cutaneous ageing. In this double-blind, placebo-controlled trial, 60 women aged 35–60 years were randomized to receive oral dietary supplement ( n  = 30) or placebo ( n  = 30), once daily for 12 weeks. The depth of skin roughness and fine wrinkles were measured using surface evaluation of skin parameters for living skin (Visioscan) at baseline, and at the 4, 8 and 12 weeks of treatment. Surface evaluation using a replica film (Visiometer) at baseline and at the 12th week of treatment was also carried out. Statistical differences in objective skin improvement were assessed by the independent t -test. The volunteers' satisfaction was tested using the chi-squared test. The baseline depth of skin roughness and fine wrinkles in the treatment group and the placebo group were 100.5 and 100 μm, respectively. At the end of the study, the depth of skin roughness and fine wrinkles in the treatment group showed a 21.2% improvement, whereas improvement in the control group was 1.7%. This difference was statistically significant ( P  < 0.001). With regard to the volunteers' satisfaction, there was no statistically significant decrease in the homogenization of skin colour, however, a statistically significant reduction in pore size and depth of skin roughness and fine wrinkles were observed ( P  < 0.05). No side effects were noted throughout the study. The oral dietary supplement containing antioxidants, minerals and glycosaminoglycans improved skin roughness and fine wrinkles but did not affect skin colour change in female volunteers.     

Distinct locational differences observable in biophysical functions of the facial skin: with special emphasis on the poor functional properties of the stratum corneum of the perioral region

The face is composed of complicated anatomical components, presenting unique portions, such as the eyes, nose and mouth in a relatively narrow area. Moreover, the facial skin is densely populated by the pilosebaceous units and sweat glands, and its stratum corneum (SC) is much thinner than that of the trunk and limbs, although it is always exposed to the environment. Among various portions of the facial skin, some are more easily irritated than others by environmental stimuli, or are more often affected by certain dermatoses. However, the functional aspects of the different portions of the facial skin have not been studied in detail under a strictly controlled environment in sufficiently large numbers of subjects covering different age groups. Thus, we conducted studies in winter with various biophysical techniques, such as transepidermal water loss (TEWL), as a parameter for SC barrier function, high-frequency conductance as that for skin surface hydration state, skin surface lipids, pH, blood flow and skin surface temperature on the forehead, mid-portion of the cheek (cheek in short), nasal tip (nose in short), nasolabial fold and chin of 20 healthy Japanese females aged 22-37 years (average 25 years) in a climate chamber adjusted to 21 degrees C and 50% relative humidity. Thereafter, we studied the influence of ageing on these biophysical parameters by collecting data of TEWL, high-frequency conductance and size of superficial corneocytes on the cheek, nasolabial fold and chin of 303 healthy Japanese female volunteers of different ages. The obtained results showed that the barrier function of the SC was best on the cheek, presenting the lowest TEWL, which was significantly higher on the nasolabial fold and chin than on the cheek. TEWL showed a decrease with age. In contrast, skin hydration state was higher on the nose, but it tended to be lower on the nasolabial fold, showing a mild age-related increase. The corneocytes on the nasolabial fold and chin were smaller than those on the cheek. They revealed a clear increase in size with age. Skin surface lipids were richest on the nose, whereas the superficial pH on the nose was the lowest among the regions tested. The skin temperature was lowest on the cheek than on other areas of the face; although, together with the nose, its blood flow was higher than that of the others. These data indicate great regional differences observable in SC functions on the face. In general, the SC barrier function increases with age, probably because of a decreased epidermal turnover rate as recognized by the increase in corneocyte size. Among the various sites, the skin of the nasolabial fold and chin, whose SC consisted of the smallest corneocytes, showed poorest SC properties in barrier function, suggesting the presence of mild invisible inflammation. It is understandable that this area easily develops not only the complaint of sensitive skin to cosmetics but also dermatitis because of various external agents.     

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     

Real-life use of underwear treated with fabric softeners improves skin dryness by decreasing the friction of fabrics against the skin

Scientific evaluation of fabric softener use on the friction of fabrics and on dry skin in real life is very limited. The coefficient of friction of fabrics was measured with a surface tester using model skin and cotton fabrics. The effects and safety of fabric softener-treated T-shirts on subjects with dry skin were evaluated in real-life conditions in the cold and arid environment. Twenty male volunteers with dry skin used T-shirts without softener for 1 week before day 0 and then wore softener-treated T-shirts for 14 days. Effects were evaluated by clinical grading, subjective symptoms, stratum corneum water content (SCWC) and transepidermal water loss (TEWL). A significant decrease in the coefficient of friction of fabrics was detected. A significant improvement in SCWC was observed on the torso, waist and shoulder, but no improvement was found on the inner forearm. There was a slight change in TEWL. The visual grading of dryness improved significantly at all sites, but no significant change was found in subjective symptoms. Our results suggest that fabric softener provides benefits to individuals with dry skin because of the decreased friction of the garments against the skin. It is possible that the softener treatment of fabrics contributes to the state of moisturization of the skin and may work in collaboration with the application of moisturizers.     

Quantification of the skin's topography by skin profilometry

A method of skin profilometry is presented. The data generated using this method are used to (a) uncover sources of variation in skin profilometry, (b) provide information regarding the choice of roughness parameters best suited for characterizing the skin's topography, and (c) determine if skin profilometry is a valuable tool for quantitatively assessing changes in the skin's surface pattern.
The data show the roughness parameter values to be dependent on the orientation of the tracings with regard to the major grooves and ridges present in the surface patterns. Large variabilities of roughness parameter values obtained for multiple scans within small areas of replicas are indicative of the nonhomogeneity of the skin's surface. The number of peaks, mean peak size, mean depth of roughness, depth of smoothness, and residual profile length appear to be the most utile roughness parameters for quantifying changes in the skin's topography. The ability of skin profilometry to detect subtle changes in the skin's surface pattern due to hydration indicates the method is a sensitive means of quantifying the skin's topography.
Quantification de la topographie de la pedu par la profilométrie de la pedu     

Evaluation of the efficacy of orange roughy (Hoplostetbus atlanticus) oil in subjects with dry skin

Moisturizers have beneficial effects in treating dry skin. The objective of this study was to evaluate the effect of orange roughy (Hoplostethus atlanticus) oil, a marine-derived wax ester, on skin dryness in comparison with a reference commercially available petrolatum-based moisturizer (Vaseline) and untreated control. Subjects (n = 24) with moderate to severe skin dryness at the lower limb of legs (Study 1) and with certain degree of skin dryness on the face and the forearms (n = 22, Study 2) were treated twice a day for 42 consecutive days with the test products in randomized clinical trials. Transepidermal water loss (TEWL) was measured at the beginning and the end of Study 1, whereas skin hydration was measured at the beginning, after 3 and 6 weeks of the application (the end of the study) in Study 2. Changes in the skin dryness were assessed by a dermatologist using a video microscopy. In Study 1, the dryness score of skin applied with orange roughy oil improved significantly (P < 0.01) in 6 weeks. The skin looked smooth with no or little dry scaly skin. Orange roughy oil was evaluated with a 60% efficacy in treating skin dryness by the expert, which comparable to that of petrolatum (68%). No significant change in TEWL was found either in orange roughy oil or petrolatum treatment, although the values showed a tendency to improve in both cases. Similarly, the results of the skin capacitance in Study 2 showed a significant improvement of the skin symptoms after 3 and 6 weeks. These results showed that the performance of orange roughy oil in treating skin dryness was comparable to that of petrolatum.     

Perfluoropolyether phosphate: skin exfoliation after a topical pre-treatment, TEWL and skin elasticity, by in-vivo non-invasive methods

Glycolic acid (GA) and other alpha-hydroxyacids (AHAs) are common ingredients of products designed to accelerate exfoliation of the skin. It is known that acidic pHs are essential in order to increase the efficacy of AHA-based products. The formulator is, therefore, obliged to achieve a difficult balance between performance (skin exfoliation) and risks (skin irritation). In order to overcome this problem, many common organic acids, and combinations of them, have been proposed, with marginal improvements. The need for a new chemistry, in order to achieve better results, was evident, particularly from the point of view of safety. We decided, therefore, to investigate the efficacy of perfluoropolyether (PFPE) phosphate, a new acidic material, already proposed for lowering the pH without increasing skin irritation. Two gels containing PFPE phosphate at different pH values (3 and 7), an acidic gel containing GA at pH 3, and a neutral gel, without an active compound, were applied on 20 healthy volunteers and evaluated with regard to effects on the skin: *Exfoliation after a topical pre-treatment with these gels *Transepidermal water loss (TEWL) and elasticity The main conclusion of the investigation was that PFPE phosphate has effects, particularly skin exfoliation rate, quite independent of the pH, and comparable to the gel containing GA at pH 3, apparently without the typical drawbacks of AHAs.     

Natural skin surface pH is on average below 5, which is beneficial for its resident flora

Variable skin pH values are being reported in literature, all in the acidic range but with a broad range from pH 4.0 to 7.0. In a multicentre study (N = 330), we have assessed the skin surface pH of the volar forearm before and after refraining from showering and cosmetic product application for 24 h. The average pH dropped from 5.12 +/- 0.56 to 4.93 +/- 0.45. On the basis of this pH drop, it is estimated that the 'natural' skin surface pH is on average 4.7, i.e. below 5. This is in line with existing literature, where a relatively large number of reports (c. 50%) actually describes pH values below 5.0; this is in contrast to the general assumption, that skin surface pH is on average between 5.0 and 6.0. Not only prior use of cosmetic products, especially soaps, have profound influence on skin surface pH, but the use of plain tap water, in Europe with a pH value generally around 8.0, will increase skin pH up to 6 h after application before returning to its 'natural' value of on average below 5.0. It is demonstrated that skin with pH values below 5.0 is in a better condition than skin with pH values above 5.0, as shown by measuring the biophysical parameters of barrier function, moisturization and scaling. The effect of pH on adhesion of resident skin microflora was also assessed; an acid skin pH (4-4.5) keeps the resident bacterial flora attached to the skin, whereas an alkaline pH (8-9) promotes the dispersal from the skin.     

Study of surfactant-skin interactions by skin impedance measurements

The stratum corneum (SC) plays a very critical physiological role as skin barrier in regulating water loss through the skin and protects the body from a wide range of physical and chemical exogenous insults. Surfactant-containing formulations can induce skin damage and irritation owing to surfactant absorption and penetration. It is generally accepted that reduction in skin barrier properties occurs only after surfactants have penetrated/permeated into the skin barrier. To mitigate the harshness of surfactant-based cleansing products, penetration/permeation of surfactants should be reduced. Skin impedance measurements have been taken in vitro on porcine skin using vertical Franz diffusion cells to investigate the impact of surfactants, temperature and pH on skin barrier integrity. These skin impedance results demonstrate excellent correlation with other published methods for assessing skin damage and irritation from different surfactant chemistry, concentration, pH, time of exposure and temperature. This study demonstrates that skin impedance can be utilized as a routine approach to screen surfactant-containing formulations for their propensity to compromise the skin barrier and hence likely lead to skin irritation.     

The alkaline pH-adapted skin barrier is disrupted severely by SLS-induced irritation

The pH of the healthy skin is 5.5 and maintained by many regulatory mechanisms. The pH of the skin care product we use on a daily basis can have an influence on the skin properties. To investigate how the physical properties of skin change after the alkaline or acidic pH of the skin care products are applied on the skin for a long term, we adjusted the pH of the skin care products to 3, 5 and 8 (A, B, C), with glycolic acid and triethanolamine. For 5 weeks the skin care products were applied on 20 healthy subjects' ventral forearm and the skin physical properties were measured. After 5 weeks, skin responses to the external stress of 1% (w/v) SLS (sodium lauryl sulphate) irritation and erythema by UV were measured. Skin colour and skin UV response were not altered by the pH. However, on the C-applied site (pH 8) the transepidermal water loss of stratum corneum (SC) increased significantly, the water content increased and desquamation decreased, respectively, and the SLS significantly impaired the skin barrier in comparison with other sites. The alkaline skin care product impaired the skin barrier after repeated application over 5-week period and the skin barrier was disrupted severely by 1% SLS exposure because SC was already impaired by alkaline pH and sensitive to external stress. This suggests that the pH of daily skin care products is very important for skin barrier homeostasis.     

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.     

Effect of fluid intake on skin physiology: distinct differences between drinking mineral water and tap water

It is generally stated that drinking plenty of water has a positive influence on skin condition. However, there is no published scientific study that has investigated this matter. The aim of our exploratory 'before-after' study was to evaluate the in vivo influence of drinking more than 2 L of mineral water or ordinary tap water per day on skin physiology. Ninety-three healthy subjects were included in our prospective study. After an initial run-in phase of 2 weeks to monitor individual drinking habits, subjects had to drink 2.25 L day(-1) of either mineral water (n = 53) or tap water (n = 40) for 4 weeks. Bioengineering in vivo measurements on the volar forearm included sonographic evaluation of skin thickness and density, determination of skin surface pH, assessment of skin surface morphology, and measurement of finger circumference. Eighty-six subjects completed the study. In the mineral water group measurements revealed a statistically significant decrease in skin density. Skin thickness increased slightly, albeit not at a statistically significant level. However, when separately analysing those individuals from the mineral water group, who had routinely drunken comparably little before the start of the study, their skin thickness increased at a statistically significant level. Skin surface pH remained almost unchanged in the physiologically optimal range. In the tap water group, skin density increased significantly, while skin thickness decreased significantly. Skin surface pH decreased at a statistically significant level. While in the mineral water group finger circumference decreased significantly, measurements in the tap water group revealed a statistically significant increase. Objective skin surface morphology did not change in any group. In summary, drinking more than 2 L of water per day can have a significant impact on skin physiology. The exact effects within the skin seem to differ depending on the nature of the water ingested. Randomized, controlled, double-blind follow-up trials are warranted to confirm the findings of our exploratory pilot study.