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Comparison of different non-invasive test methods with respect to the different moisturizers on skin
Abstract
In dermatology and cosmetics, moisturizers are used to soften skin. The objectives of this study were to compare the influence of three different moisturizers on skin hydration and skin mechanics by various non-invasive test methods and to determine the relationship between the methods used.
In 27 test subjects, four test areas in each were treated over 3 days, three times a day. An oil-in-water (o/w) emulsion was applied without moisturizer, the same with 10% glycerol, with 10% urea, or with 10% propylene glycol, respectively. Three hours after the last treatment results were measured by using the following instruments: Corneometer CM 820, Skicon 200, Frictionmeter, and Cutometer.
In all procedures a significant effect, in the sense of an increase in the data recorded, could be demonstrated by glycerol-treatment. During Corneometer, Frictionmeter, and Cutometer measurements, an additional unidirectional effect caused by the basic emulsion was seen. With all test methods, the influence of urea and propylene glycol was not significant compared to the basic emulsion. For all pretreatments there was a correlation between Corneometer data and Skicon data. Because of the low correlation coefficients between hydration parameters and mechanical parameters, it is to be assumed that other effects of glycerol- and basic-emulsion-treatment-independent from the hydration effect – have an additional influence on the data obtained by using the Frictionmeter and the Cutometer. This indicates that the clinical effect of emulsions should not be evaluated exclusively on the basis of electrical measurements of hydration.
... Moreover, glycerol reduces the density and the average radius of aqueous pores in SC, hereby decreasing the ability of irritant agents to penetrate the SC [78]. In addition to moisturizing and providing barrier restoring potential, glycerol improves mechanical properties of the skin [79]). There is a correlation between SC hydration and skin mechanical properties [80]. ...
... The skin friction coefficient also shows positive correlation with SC hydration [81]. Another study suggests that the effects of glycerol on mechanical parameters may be independent of its hydrating ability [79]. Effects of glycerol have been extensively studied; however less information is available for other polyols. ...
The most important function of the skin is to form a barrier between the body and the external environment. The epidermal barrier prevents transepidermal water loss from the skin, but also serves as a barrier to the entry of harmful environmental allergic, toxic or infectious substances. Inherited defects in the genes encoding the components of the epidermal barrier result in the development of rare genetic disorders, whereas polymorphisms in these genes together with environmental factors cause frequent inflammatory skin diseases, such as atopic dermatitis. In this review, components of the skin-barrier function will be reviewed with special emphasis on how the altered epidermal barrier might be repaired. The different strategies to increase the transdermal penetration of drugs is also discussed.
... 14 In a moisturizers set of 10% urea, 10% propylene glycol and 10% glycerol in oil in water (o ⁄w) emulsions, only the latter produced a significant increase of SC hydration. 37 By measuring electrical capacitance and conductivity the authors found that, compared with basic emulsion, only the mixture containing glycerol significantly increased the measured values. ...
... Skin plasticity and deformability were studied with the use of the noninvasive instruments, Frictionmeter and Cutometer, respectively. 37 Only glycerol from the tested set of substances (glycerol, urea, propylene glycol and vehicle) had a significant beneficial effect. The observed changes were parallel to the increasing of SC hydration by glycerol. ...
Glycerol is a trihydroxy alcohol that has been included for many years in topical dermatological preparations. In addition, endogenous glycerol plays a role in skin hydration, cutaneous elasticity and epidermal barrier repair. The aquaporin-3 transport channel and lipid metabolism in the pilosebaceous unit have been evidenced as potential pathways for endogenous delivery of glycerol and for its metabolism in the skin. Multiple effects of glycerol on the skin have been reported. The diverse actions of the polyol glycerol on the epidermis include improvement of stratum corneum hydration, skin barrier function and skin mechanical properties, inhibition of the stratum corneum lipid phase transition, protection against irritating stimuli, enhancement of desmosomal degradation, and acceleration of wound-healing processes. Even an antimicrobial effect has been demonstrated. Topical application of glycerol-containing products improves skin properties in diseases characterized by xerosis and impaired epidermal barrier function, such as atopic dermatitis. The increase of epidermal hydration by glycerol is critical in skin conditions aggravated by dry and cold environmental conditions, e.g. winter xerosis. This paper provides a review on effects of glycerol on the skin, the mechanisms of its action, and the potential applications of glycerol in dermatology.
... Yilmaz and Borchert [23] demonstrated an increase in skin hydration and skin elasticity following topical application of cream containing stratum corneum lipid and ceramide 3B. Bettinger et al. [24] confirmed the result by showing positive correlation between skin capacitance and skin elasticity after treatment with glycerol emulsion. However, no correlation was detected by the treatment of urea and propylene glycol. ...
Purpose: Age and skin hydration influence skin mechanical properties. However, correlation between hydration improved by cosmetic and mechanical properties is uncertain. This study aimed to investigate the relationship between age, intrinsic skin hydrations, skin hydration after topical treatment, and skin mechanical parameters of different age ranges. Patients and Methods: A total of 123 healthy volunteers, aged 18–55, were divided into three age groups. Skin hydration and biomechanical properties were evaluated using Corneometer® and Cutometer®, respectively. Subsequently, 61 healthy women aged 30–55 were measured for skin hydration and biomechanical parameters after 8 weeks application of microemulsion or nanoemulsion. The changes in each parameter and their correlation were evaluated. Results: Skin capacitance correlated to some mechanical parameters only in young volunteers. Only gloss elasticity (R2) presented strong negative correlation with age in 30–40-year-old volunteers while all elasticity parameters (R2, R5, and R7) showed significant negative correlations with age in 41–55 years old volunteers. Microemulsion or nanoemulsion significantly improved skin hydration; however, it did not always affect elasticity parameters. Conclusion: Skin elasticity decreased with age and changes in R2 were firstly observed. Decrease in R2 parameter could, then, be the first sign of skin aging. Skin hydration and elasticity were not related in any age. Improvement in skin hydration and elasticity by topical treatment was independent and based on individual formulation. © 2018, Faculty of Pharmaceutical Sciences, Chulalongkorn University. All rights reserved.
... Bettinger et al. reported that 10 glycerol in oil-in-water emulsions significantly increased stratum corneum hydration compared with 10 urea and 10 propylene glycol, as measured by electrical capacitance 13 . ...
The water content of the stratum corneum was measured to investigate the skin-moisturizing property of diglycerol in water and in a lotion. The water content of the stratum corneum, to which the diglycerol solution was applied, was lower than that of the glycerol solution for 8 h. However, skin treated with diglycerol in combination with glycerol solution maintained a higher capacitance level compared with that of glycerol solution alone after 8 h. Moreover, the long-term moisturizing effect of the stratum corneum prominently appeared when diglycerol was formulated to the lotion containing glycerol and 1,3-butylene glycol. These studies suggest that diglycerol in combination with glycerol has a long-term moisturizing effect on human skin.
... R0 demonstrates a positive correlation with hydration (18) and can be used as a marker in the study of hydrating agents (19). However, another study has suggested that the effects of glycerol on the mechanical parameters may be independent of its hydrating ability (20). Thus, the plasticity and distensibility of the skin may be influenced not only by hydration, but also by other mechanisms. ...
Glycerol and xylitol hydrate the skin and improve its barrier function over a short period. We studied the effects of glycerol and xylitol on the physiological properties and morphology of the skin after longer-term application. Twelve volunteers with dry skin were examined. Three areas on the arms were determined. Area 1 served as untreated control. The vehicle was applied to area 2, while area 3 was treated twice daily with a formulation containing glycerol (5%) and xylitol (5%) for 14 days. Transepidermal water loss (TEWL), hydration and biomechanical properties of the skin were monitored. Biopsies were taken for routine histology and immunohistochemistry for filaggrin and matrix metalloproteinase-1 (MMP-1). The polyols increased the skin hydration and protein quantity of filaggrin, elevated the interdigitaion index, decreased the TEWL and improved the biomechanical properties of the skin, but did not change the protein expression of MMP-1. A combination of glycerol and xylitol can be useful additional therapy for dry skin.
... 피부에 존재하는 수분의 정도에 따라 다른 전기적 성질을 가지는 데에 있어서 개발된 방법들로서 피부의 전기용량(capacitance) [1][2][3][4][5], 전기전도도(conductance) [6], 임피던스(impedance) [7][8] butylenes glycol influenced directly the hydration increase rate in the SC previously. In this study, glycerol was used to prepare the standard products from 0 to 20 percents and applied to the same volunteers. ...
The measurement of hydration level in the surface layer of the skin, stratum corneum (SC), gives important information on the biophysical properties and function of the skin barrier such as softness, flexibility, and healthiness of the skin. But it is difficult to measure a consistent hydration level from a sample to another sample due to individual variations and environmental changes. The aim of this study was to evaluate objective hydration after using various products in the SC. The SC Hydration was measured by capacitance (Corneometer^{(R)}, C+K, Germany) on the ventral site of forearm from 40 healthy volunteers. The skin surface was chronologically measured immediately after application of the test products and 3 and 6 hours later. We analyzed the averages of five measurements of each site and used the hydration increase rate for correction on untreated site variation. We found that most polyols including glycerol and butylenes glycol influenced directly the hydration increase rate in the SC previously. In this study, glycerol was used to prepare the standard products from 0 to 20 percents and applied to the same volunteers. The individual standard curve showed linear relation to glycerol concentrations. Based on the the standard curve, hydration of SC was converted into hydration increase rate to glycerol concentrations. The converted glycerol concentrations of products were repetitive and reproducible. In addition, the individual standard curve was used to relate the skin type of each individual. These results suggest that the hydration of the SC standardized regardless of external variation and individual skin condition can explain detailed skin state variation. Further studies will be conducted with other ingredients such as surfactants, lipids and aqueous materials, and with other methods for noninvasive measurement.
... Both formulations (oil-in-water emulsion and peel-off facial mask) have components that change the structure of the stratum corneum, such as glycerol and propylene glycol [19]. It is also known that polyols are highly hygroscopic, because they form hydrogen bonds with water [20], promoting increased concentration of water on the surface of the skin [21], as well as increased tenderness and softness [22]. Thus, it was expected that TEWL would decrease due to the increased amount of water in the skin due to the presence of polyols in both formulations. ...
Synopsis Objective
This study aimed to compare the efficacy of a peel-off facial mask based on polyvinyl alcohol (PVA) with an oil-in-water (o/w) emulsion and the effect of a soybean extract fermented by Bifidobacterium animale incorporated in those formulations (5% w/w). Methods
The formulations were submitted to randomized clinical studies in volunteers to evaluate the measurement effects as (a) tensor by Cutometer((R)), (b) moisturizing by Corneometer((R)) and transepidermal water loss (TEWL) by Tewameter((R)). These effects were determined in a short-term study (3h) in a controlled-temperature room. ResultsThe tensor effect and TEWL values indicated no significant difference between the use of facial mask and emulsion. On the other hand, the moisturizing effect of the facial mask on the stratum corneum was more significant than that of the emulsion according to Corneometer((R)) measurements. Biometric cutaneous evaluation of peel-off facial masks (short-term study) showed that the masks promoted moisturizing effect of the stratum corneum more effectively than the oil-in-water emulsions. Thus, the facial masks were more efficient than emulsions in relation to moisturizing effects, but this efficiency is not related to the presence of fermented soybean extract. Conclusion
The results indicated that peel-off facial masks increase skin hydration in a process related to the occlusive effect.
... It is regarded as a reliable measure of skin conditions and also this method gained validity and use diffusion in dermatology and cosmetics [37][38][39]. The reliability and the reproducibility of these measures were previously demonstrated [40][41][42]. ...
Background and Aims: A gynaecological cream containing collagen, phytocollagen, hyaluronate and vitamins was investigated in women in menopause. Methods: The cream was daily applied to the vaginal mucosa and the perineal skin as well as to the abdominal skin (healthy skin used as control) for 1 week and then on alternate days for other 2 weeks. Skin hydration and viscoelasticity were measured at baseline and after 8 and 21 days by Corneometer? CM 825 and Cutometer? MPA 850, respectively. The product use comfort and the moisturising of the vaginal mucosa were evaluated by the volunteers through a questionnaire and a visual analogue scale, respectively. Results: The local tolerability was excellent for nearly all of the volunteers (90% - 95%) and according both to dermatologist’s and gynaecologist’s evaluation. Related adverse reactions had a frequency of 15% (10% vulvovaginal burning sensation and 5% vulvovaginal discomfort). The topical hydration increased both in the perineal and the abdominal skin. Hydration increase vs. baseline was more marked on day 8 than on day 21 and was significant in the abdominal skin (p-value < 0.0001). The vaginal moisturising improved significantly (p-value < 0.0001) both on day 8 and 21 vs. baseline. Small changes in the viscoelasticity parameters were observed in both the perineal and the abdominal skin. Few significant improvements were R1 and R8 decreases in the perineum and R0 increase in the abdomen. Conclusions: The tested cream represents a safe product with proven moisturising effect towards the vaginal mucosa when daily applied by menopausal women.
... Other studies found comparable values for the skin hydration. Bettinger [25] obtained higher values for the hydration on the proximal forearm, with a median skin hydration of 79.3 AU for untreated skin. The hydration of the index finger measured in the current study of 78.4 is comparable to the Corneometer values of 70 AU reported by Kuilenburg et al. [6]. ...
The human skin is constantly in interaction with materials and products. Therefore, skin friction is relevant to all people. In the literature, the frictional properties of the skin have been linked to a large variety of variables, like age, gender and hydration. The present study compares the data of 450 skin friction measurements with the skin hydration and skin temperature on four locations on the body, measured with four materials: stainless steel (SST), aluminum (Al), PE and PTFE. The median skin temperature was 32.1 °C and the median skin hydration was 25.5 AU, as measured with a Corneometer. The median coefficient of friction was 0.52 for the static coefficient of friction and 0.36 for the dynamic coefficient of friction. There was a linear relationship between those two types of coefficient of friction. The coefficient of friction was highest for SST and lowest for PTFE. The frictional properties depend on the skin hydration and skin temperature. Gender differences were found for both skin hydration and coefficient of friction. Most of the variation in the coefficients of friction could be explained by the differences in hydration.
... Several in vivo studies using modern bioengineering techniques have been performed to evaluate the mechanical properties and water content of the epidermis.[12–15] Instruments that have been used for assessing epidermal hydration are based on measurements of conductance,[16] capacitance,[1217–19] and impedance[20] of the skin. Instruments that have been used for testing skin (viscoelasticity) mechanical properties are based on torsion[21] and suction methods.[12–21] ...
A number of moisturizers are available containing natural hydrating, moisturizing, fi rming and occlusive property-imparting agent in the form of herbal extracts, juice and oils. The aim of this study is to assess the hydration and viscoelastic effect of commercially available herbal moisturizers, containing different herbs, on human skin, after a single and 3-week period of application using skin bio mechanical and electrical techniques.
Twenty selected herbal moisturizers (HM) were coded as HM1-HM20. Forty volunteers, mean age of 40 ± 9 years, were participated in the short- and long-term study. Skin properties in terms of hydration and viscoelastic parameters were measured by multitester and cutometer, respectively. Measurements were done before and after 1, 2, and 3 h (single application) and for the 3-week period of daily application.
After single application, significant increase has been observed in both the skin electrical (P < 0.001) and mechanical properties (P < 0.01) as compared to the control, at which no products were applied. After the 3-week period, both effects are maintained and found to be significant at P < 0.001. Short-and long-term study revealed that out of 20 herbal moisturizers, HM8 and HM10 show pronounced increase in skin hydration (90-100%) and HM8, HM10, and HM11 shown marked increase in skin viscoelasticity (90-95%). CONCLSUION: The possible reason of maximum effects obtained by these products is multifunctional effects of active ingredients of incorporated herbs. Combined used of both non invasive techniques is useful to substantiate the hydrating and viscoelasticity claim of herbal moisturizer. Short- and long-terms study revealed the best performing herbal moisturizer.
... In addition, glycerol has a safe toxicological profile [1][2][3][4] . In the literature, a variety of positive skin properties are summed up for glycerol, including its hygroscopicity, its stratum corneum humectancy, enhancing skin smoothness and improvement of the skin barrier function [5][6][7][8][9] . Due to its action as a hygroscopic compound, glycerol is capable of attracting and retaining water and is efficient in alleviating dry skin conditions [10][11][12] . ...
Hydrocolloid patches are developed with 10, 20 and 30% (w/w) glycerol as the main active ingredient. By making use of two experimental forearm models, skin efficacy and its dependency on the glycerol concentration applied were compared with a blank reference patch, a commercialized protective patch and a cosmetic barrier cream. Skin hydration and transepidermal water loss measurements were combined with skin erythema assessments. After a single application to healthy skin, a clear concentration-dependent effect of glycerol-containing patches was observed with - for the highest glycerol content - a 31% increase in skin hydration and an improvement in skin barrier properties of 15%. This glycerol-containing patch also accelerated barrier recovery of mechanically irritated skin after stripping with cyanoacrylate tape. After 7 days of repetitive application, a significantly hydrating effect of the 30% glycerol-containing patch was observed, which was of the same order of magnitude as observed for the cosmetic barrier cream, the latter being applied twice daily. The effects seen were maximal after 3 days of patch application.
... The influence of the hydration level of the stratum corneum (SC) on skin mechanical properties has been known for a long time (12)(13)(14)(15)(16)(17). However, several authors report a lack of strong correlation and of clear direct interdependence between both measurements (6,12,(18)(19)(20). This may be due to the use of different instruments for measuring mechanical and electrical properties of the skin, to different levels of skin hydration in the various studies, to the use of different mechanical parameters considered by the authors and to the fact that skin biomechanics is not only influenced by skin hydration. ...
The Reviscometer RVM600 that measures resonance running time (RRT) has been shown to be inversely related to the skin stiffness. However, very few publications describe the use of this instrument for testing the effect of cosmetic products.
Slight xerotic skin condition was induced by using an alkaline soap for 1 week. Skin has then been rehydrated with a lotion or further dehydrated and dried with sodium lauryl sulfate (SLS). Skin condition at the different stages of the study was evaluated by visual assessment for dryness and redness and by non-invasive methods (Corneometer, Cutometer, Reviscometer, Evaporimeter and squamometry).
All methods showed highly significant changes after the slight drying phase with the soap usage. They illustrated skin repair after lotion treatment and further skin impairment after SLS application. Nevertheless, the Reviscometer was able to better statistically discriminate between the treatments (water, lotion, SLS) than the Cutometer . Measurement of the RRT along the transversal axis of the forearms was the most sensitive for differentiating between normal and dry skin and between the treatments on the basis of skin mechanical properties.
The Reviscometer RVM600 is a sensitive instrument able to detect slight skin surface effect of cosmetics. Combined with published literature on the interpretation of RRT measurements on polymeric gel or in different skin conditions (elderly skin and photoaged skin), the Reviscometer looks to be a recommendable instrument to measure slight changes in SC stiffness/suppleness induced by cosmetic products.
Introduction
This study investigated the role of natural polymers as moisturizers with low toxicity and biodegradability in the cosmetic and pharmaceutical industries. We isolated a polysaccharide extract from Dendrobium candidum (D. candidum) and determined its efficacy in skin hydration when used as an active cosmetic ingredient.
Methods
The molecular weight distribution of D. candidum polysaccharides was analyzed via gel permeation chromatography (GPC). We performed real-time reverse transcription PCR (RT-PCR) and western blotting assays to investigate the physiological mechanism of the polysaccharides extracted from D. candidum (PDC). Based on in vitro data, the efficacy of PDC in improving skin condition was tested on the face of 21 volunteers.
Results
The expression of filaggrin (FLG), caspase-14, and bleomycin hydrolase, which are the major components contributing to skin hydration, was significantly increased in the PDC-treated group. Further, the PDC upregulated the mRNA expression of occludin and claudin-1, which play a key role in epidermal barrier function. In addition, a topical application of PDC markedly increased skin hydration and improved trans-epidermal water loss (TEWL) and skin elasticity after 2 weeks.
Conclusions
It is the first study reporting the efficacy of PDC-mediated FLG mechanism associated with positive skin hydration. PDC can be used as an active ingredient in moisturizers. Long-term application of PDC-based moisturizers may result in significant improvement in elasticity and barrier function.
Background
The work is aimed at the development of a methodology to characterize the tactile properties of topical products during application. Specific attention was paid to the study of the residual properties left at the surface of the skin. This approach was interestingly used to better understand the formulation factors governing the skinfeel of topical preparations.
Materials and Methods
Cosmetic and pharmaceutical topical products were selected based on their various texture, galenic form (gel or emulsion), and composition (polymer used as texturing agent). Key texture attributes namely Firmness, Stickiness, Spreadability, and Amount of residue were objectively evaluated using sensory analysis. Additionally, texture analysis (compression test), rheology (flow test), and tribology (in vivo friction test) were carried out.
Results
Sensory evaluations highlighted a great diversity of tactile properties among products when applied to skin. For example, assessors perceived an important amount of residue left by emulsions whereas gels were not leaving any residue after application to the skin. These results were confirmed by in vivo tactile friction measurements with two distinct evolutions in time of the residual film properties.
Conclusion
The present investigation shows how the tactile properties of topical gels and emulsions are studied using complementary tests in order to understand and improve the skinfeel of topical preparations.
Bacterial cellulose (BC) has been applied for wound dressing application. In this study, physical and biological properties of the BC dressing were improved by incorporation of silk sericin (SS), polyhexamethylene biguanide (PHMB), and glycerin. The glycerin incorporation reduced dehydration rate and wound adhesion of the BC dressing in a concentration-dependent manner. PHMB, an antiseptic agent, provided antibacterial activity against gram-positive and gram-negative bacteria. Meanwhile, SS would enhance collagen and tissue formation in wounds. Finally, we confirmed that the BC dressing incorporating SS, PHMB, and glycerin was safe to be used as a medical material according to ISO 10993-6 standard.
Introduction:
Foot blisters are a common injury, which can impact on activity and lead to infection. Increased skin surface hydration has been identified as a risk factor for blister formation, indicating that a reduction in hydration could reduce the risk of blister.
Method:
Thirty healthy adults were randomised into 3 groups, each receiving a preventative foot blister treatment (2Toms(®) Blister Shield(®); Flexitol(®) Blistop and Boots Anti-Perspirant Foot Spray). Cycles of compression and shear loads where applied to heel skin using a mechanism driven by compressed air. Temperature changes were measured during load application using a thermal imaging camera (FLIR Systems Inc. and Therm CAM™ Quick Report). Near surface hydration of the skin was measured using a Corneometer(®) (C & K, Germany).
Results:
There was no significant difference in the rate of temperature change of the skin between the three groups compared to not using products (p = 0.767, p = 0.767, p = 0.515) or when comparing each product (p = 0.551). There was a significant decrease in near surface skin hydration, compared to baseline, after the application of powder (-8.53 AU, p = 0.01). There was no significant difference in hydration after the application of film former and antiperspirant (-1.47 AU, p = 0.26; -1.00 AU, p = 0.80, respectively).
Conclusion:
With the application of external load we found no significant difference in the effect of the three products on temperature change. The powder product demonstrated an effect on reducing the risk of blister. It is postulated that powder may have a barrier effect.
Glycerol, obtained mainly by saponification of oils and fats, is an important ingredient in pharmaceutical and cosmetic preparations. It acts as a humectant due mostly to its high hygroscopic property. Actually, endogenous glycerol in the skin is widely studied. The importance of endogenous glycerol is now established in the stratum corneum (SC) hydration. In humans, the glycerol skin content is correlated to sebaceous gland density. SC glycerol is mostly provided by triglycerides lipolysis in sebaceous gland and also sparsely by the breakdown of phospholipids by phospholipases. Glycerol diffuses from dermis and is transported into basal layers of the epidermis through aquaporin 3 (AQP3), a transmembrane water/glycerol transporting protein. Furthermore, AQP3-facilitated glycerol transport is involved in epidermal cell proliferation during repair of skin wounds. It is actually known that the skin care benefits of glycerol are due to different properties of the compounds: attraction of moisture, maintenance of crystallinity/fluidity of cell membranes and intracellular lipids, keratolytic effect, and its ability to diffuse and penetrate into the SC. Glycerol prevents damaging effect on the SC and leads to a more rapid reconstitution of the protective skin barrier following mechanical or chemical damage by generating stimulus for barrier repair. The water holding capacity of SC is related to hygroscopic compounds and to SC osmotic pressure. Glycerol could be helpful in atopic dermatitis treatment.
Background
Friction blister research has focused on prevention and treatment approaches rather than exploring the pathophysiology of the friction blister. Increased skin hydration has been purported to be a key risk factor in friction blister development. This study aimed to test the effect of increased skin surface hydration on the risk of friction blister creation.Methods
The skin on one foot was hydrated by soaking the foot in water. Intermittent loading was carried out until an observable change of 3°C was evident using infrared thermography. The contra lateral foot acted as a control. Skin hydration and elasticity was measured using electrical capacitance and negative pressure respectively.ResultsThe rate of temperature change of the hydrated group was significantly greater than that of the non-hydrated foot group (P = 0.001) and showed a strong positive correlation (r = 0.520) with skin surface hydration. Weak negative correlations were seen between skin elasticity and rate of temperature change in response to load application (r = −0.166) and skin surface hydration and elasticity at baseline (r = −0.195).Conclusion
In controlled experimental conditions increased skin surface hydration increases the rate of temperature change of the skin in response to load application and consequently increases the risk of blister creation.
In daily life, cosmetics can play important roles in facial skin moisturizing, whitening and sun protecting. Unfortunately, the aged skin stratum corneum (SC) often impedes the penetration for cosmetics. Regular removal of the extra aged horny cells can facilitate the penetration for cosmetics and improve the performance of the skin. However, no study has assessed the detailed effects of exfoliating facial cleanser on the friction properties of human skin and the degree of aged SC removal. In this paper, the effects of three kinds of scrub facial cleanser with different sizes, amounts and hardness scrub particles on the tribological properties of human skin have been investigated in vivo using a UMT-II tribometer under the simulated face washing conditions. The hardness of the scrub particles were measured by using a Nano-Hardness/Scratch Tester. The results showed that the aged SC has all been removed by the three kinds of scrub cleanser under the reciprocating sliding wear mode, which resulted in decrease of skin surface roughness and increase of skin conductance and hydration. Thus, the adhesion force and friction coefficient between the hydrated skin and a probe increased due to the increased contact area and skin hydration. Compared with the other two cleansers, the cleanser with two kinds of size and moderate hardness scrub particles made the skin to deform more elastically and removed more aged SC, which led to greater decrease in skin surface roughness and greater increase in skin conductance, hydration and adhesion. Hence the skin friction coefficient and penetration were higher and the moisturizing persistence lasted longer time after the same moisturizer was used. This indicated that the properties of scrub particles in cleanser played important roles in skin tribological behavior and penetration. The results may be instrumental in developing and testing skin cosmetics.
Background
The frictional characteristics of skin‐object interactions are important when handling objects, in the assessment of perception and comfort of products and materials and in the origins and prevention of skin injuries. In this study, based on statistical methods, a quantitative model is developed that describes the friction behaviour of human skin as a function of the subject characteristics, contact conditions, the properties of the counter material as well as environmental conditions.
Aims
Although the frictional behaviour of human skin is a multivariable problem, in literature the variables that are associated with skin friction have been studied using univariable methods. In this work, multivariable models for the static and dynamic coefficients of friction as well as for the hydration of the skin are presented.
Materials & Methods
A total of 634 skin‐friction measurements were performed using a recently developed tribometer. Using a statistical analysis, previously defined potential influential variables were linked to the static and dynamic coefficient of friction and to the hydration of the skin, resulting in three predictive quantitative models that descibe the friction behaviour and the hydration of human skin respectively.
Results and Discussion
Increased dynamic coefficients of friction were obtained from older subjects, on the index finger, with materials with a higher surface energy at higher room temperatures, whereas lower dynamic coefficients of friction were obtained at lower skin temperatures, on the temple with rougher contact materials. The static coefficient of friction increased with higher skin hydration, increasing age, on the index finger, with materials with a higher surface energy and at higher ambient temperatures. The hydration of the skin was associated with the skin temperature, anatomical location, presence of hair on the skin and the relative air humidity.
Conclusion
Predictive models have been derived for the static and dynamic coefficient of friction using a multivariable approach. These two coefficients of friction show a strong correlation. Consequently the two multivariable models resemble, with the static coefficient of friction being on average 18% lower than the dynamic coefficient of friction. The multivariable models in this study can be used to describe the data set that was the basis for this study. Care should be taken when generalising these results.
Some nonserious skin infections can be treated by hydration and antibacterial control. Microcapsules containing aloe-chitin are often used to treat this kind of problem. Microcapsules were applied to cotton fabrics by padding and sleeves were prepared. A hypoallergenic test was applied to the microcapsule emulsion and hydration of the epidermis was evaluated by capacitance methods. The fabric was sterilized by electron beam treatment to satisfy the antibacterial requisite. The results showed that the aloe is transferred from the fabric to the skin, increasing the level of skin hydration. The electron beam method was also shown to be effective for bacteria and fungi and had no effect on the microcapsule properties. It can, therefore, be confirmed that electron beam sterilization has no harmful effects on the type of microcapsule used in this study. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
A thorough examination of the skin is essential for accurate disease diagnostics, evaluation of the effectiveness of topically applied drugs and the assessment of the results of dermatologic surgeries such as skin grafts. Knowledge of skin parameters is also important in the cosmetics industry, where the effects of skin care products are evaluated. Due to significant progress in the electronics and computer industries, sophisticated analytic devices are increasingly available for day-to-day diagnostics. The aim of this article is to review several advanced methods for in vivo skin analysis in humans: magnetic resonance imaging, electron paramagnetic resonance, laser Doppler flowmetry and time domain reflectometry. The molecular bases of these techniques are presented, and several interesting applications in the field are discussed. Methods for in vivo assessment of the biomechanical properties of human skin are also reviewed.
In order to visualize the effects of aqueous surfactant-humectant systems on the skin barrier, an in vitro two-photon fluorescence microscopy (TPM) study, including dual-channel visualization, was carried out. TPM is a non-invasive imaging technique based on two-photon induced nonlinear excitations of fluorophores, with the capability for deep-tissue imaging (up to several hundred micrometers). The following aqueous solutions of surfactants, a humectant, and a surfactant+humectant mixture that contacted pig full-thickness skin (p-FTS) were studied: (i) a harsh surfactant solution-sodium dodecyl sulfate (SDS) (1 wt%); (ii) a harsh surfactant+humectant solution-SDS (1 wt%) + glycerol (10 wt%); (iii) a mild surfactant solution-sodium cocoyl isethionate (SCI) (1 wt%); (iv) a control solution-phosphate-buffered saline (PBS); and (v) a humectant solution-glycerol (10 wt%). Sulforhodamine B (SRB), a hydrophilic fluorescent probe, was used to visualize the effects of aqueous contacting solutions i-v on the skin barrier morphology. The results of the TPM visualization study revealed that SDS induces corneocyte damage by denaturing keratins and creating intracorneocyte penetration pathways. On the other hand, SDS+glycerol did not significantly induce corneocyte damage. The dual-channel TPM images corresponding to aqueous contacting solutions iii-v showed low SRB penetration into the corneocytes, as well as localization of the SRB probe within the lipid bilayers surrounding the corneocytes of the SC. Through a quantification of the amount of SRB that penetrated into the skin as a function of skin depth, we found that adding glycerol to an SDS aqueous contacting solution can significantly reduce the SDS-induced penetration depth of SRB, which provides evidence of the ability of glycerol to mitigate SDS-induced skin barrier perturbation. The distribution of SRB in the p-FTS samples was analyzed using a theoretical model that quantified changes in the skin aqueous pore characteristics induced by aqueous contacting solutions i, ii, iii, and v, relative to aqueous contacting solution iv, the control. The results of the theoretical model indicate the following ranking order in the extent of perturbation to the skin aqueous pores (from the highest to the lowest): i > ii > iii > iv > v. The development of such an in vitro visual ranking methodology, including quantification using TPM, can potentially reduce many costly in vivo screening procedures, thereby significantly reducing the cost and time-to-market of new cosmetic formulations containing surfactants and humectants.
Two studies were performed to evaluate the influence of glycerol on the recovery of damaged stratum corneum barrier function. Measurements of transepidermal water loss and capacitance were conducted in a 3-day follow-up after tape stripping (study 1) and a 7-day follow-up after a barrier damage due to a repeated washing with sodium lauryl sulphate. In study 1 a faster barrier repair (transepidermal water loss) was monitored in glycerol-treated sites. Significant differences between glycerol open vs. untreated and glycerol occluded vs. untreated were observed at day 3. Stratum corneum hydration showed significantly higher values in the sites treated with glycerol+occlusion, compared with all other sites. In study 2 a faster barrier repair was seen in glycerol-treated sites, with significant differences against untreated and base-treated sites 7 days after the end of the treatment. Stratum corneum hydration showed highest values in the glycerol treated sites after 3 days of treatment. Glycerol creates a stimulus for barrier repair and improves the stratum corneum hydration; stratum corneum hydration is not strictly related to barrier homeostasis and can be optimized by different mechanisms and pathways. The observed effects were based on the modulation of barrier repair and were not biased by the humectant effect of glycerol. As the glycerol-induced recovery of barrier function and stratum corneum hydration were observed even 7 days after the end of treatment, glycerol can be regarded as a barrier stabilizing and moisturizing compound.
Background/aims: The Cutometer equipped with a 2-mm diameter suction probe is a device suitable for assessment of epidermal mechanics. The objectives of this study were to determine the sensitivity of Cutometer parameters to epidermal hydration, to evaluate the correlation between skin mechanical parameters and skin capacitance, and to study the role of pretension of the skin.
Methods: In the first study, skin capacitance (Corneometer) and 10 mechanical parameters were determined before and 60 min after application of five different moisturizers on the volar forearm. In the second study, measurements of epidermal mechanics were made without and with 0.1 s presuction of the skin, before and 120 min after application of petrolatum and glycerin.
Results: Hydration of the skin significantly increased the values of capacitance and all rheological parameters. Delayed distension (Uv) and viscoelastic-to-elastic ratio (Uv/Ue) were the most sensitive Cutometer parameters. Significant correlations between skin capacitance and mechanical parameters were not found. Pretension of the skin did not significantly influence the values of skin mechanical parameters.
Conclusions: The non-invasive measurements of skin elasticity are appropriate for an objective and quantitative evaluation of the complex effect of different dermatological and cosmetic products on skin mechanics and hydration.
The stratum corneum (SC) serves as the skin barrier between the body and the environment. When the skin is contacted with an aqueous solution of the surfactant sodium dodecyl sulfate (SDS), a well-known model skin irritant, SDS penetrates into the skin and disrupts this barrier. It is well established, both in vitro and in vivo, that the SDS skin penetration is dose-dependent, and that it increases with an increase in the total SDS concentration above the critical micelle concentration (CMC) of SDS. However, when we added the humectant glycerol at a concentration of 10 wt% to the aqueous SDS contacting solution, we observed, through in vitro quantitative skin radioactivity assays using (14)C-radiolabeled SDS, that the dose dependence in SDS skin penetration is almost completely eliminated. To rationalize this important observation, which may also be related to the well-known beneficial effects of glycerol on skin barrier perturbation in vivo, we hypothesize that the addition of 10 wt% glycerol may hinder the ability of the SDS micelles to penetrate into the skin barrier through aqueous pores that exist in the SC. To test this hypothesis, we conducted mannitol skin permeability as well as average skin electrical resistivity measurements in vitro upon exposure of the skin to an aqueous SDS contacting solution and to an aqueous SDS + 10 wt% glycerol contacting solution in the context of a hindered-transport aqueous porous pathway model of the SC. Our in vitro studies demonstrated that the addition of 10 wt% glycerol: (i) reduces the average aqueous pore radius resulting from exposure of the skin to the aqueous SDS contacting solution from 33 +/- 5 Angstrom to 20 +/- 5 Angstrom, such that a SDS micelle of radius 18.5 +/- 1 Angstrom (as determined using dynamic light-scattering measurements) experiences significant steric hindrance and cannot penetrate into the SC, and (ii) reduces the number density of aqueous pores in the SC by more than 50%, thereby further reducing the ability of the SDS micelles to penetrate into the SC and perturb the skin barrier.
The efficacy of cosmetics on human skin measured under normal mild laboratory environment might be discounted by exterior environment factors such as wind, UV exposure, etc. Few studies have focused on the 'genuine' efficacy of cosmetics on human skin during exposure to external rigorous environment. The aim of this study was to develop a model for the evaluation of the efficacy of cosmetics on human skin under simulated rigorous environment.
We measured skin water content and transepidermal water loss (TEWL) before and after products application under simulated windy and sub-erythema UV exposure treatment in a constant temperature and humidity laboratory.
The results showed that the products had higher water content and lower TEWL at 2, 4 and 8 h of products application, and ameliorated the skin moisturization situation after a 3-week continuous use of the products. In addition, the products might protect the skin to maintain the normal water content and TEWL under the simulated windy or sub-erythema UV exposure treatment in our laboratory when compared with untreated area.
Our data indicate that this model may provide a more accurate evaluation for the genuine moisturizing effect of cosmetics under external natural climate.
We propose that skin electrical current measurements can be used in vitro to effectively rank aqueous solutions containing surfactants and humectants (the enhancer) contacting the skin, relative to a PBS aqueous solution (the control) contacting the skin, based on their ability to perturb the skin aqueous pores. Specifically, we develop an in vitro ranking metric using the increase in the skin electrical current induced by an enhancer relative to the control. Aqueous contacting solutions containing (i) surfactants [SDS (sodium dodecyl sulfate)] and C(12)E(6) [dodecyl hexa (ethylene oxide)], (ii) humectants (glycerol and propylene glycol), and (iii) a control (PBS) were studied. Utilizing the new in vitro ranking metric, these aqueous contacting solutions were ranked as follows (from the mildest to the harshest): glycerol < propylene glycol < PBS < C(12)E(6) < SDS. In order to further develop this ranking methodology, which can potentially lead to the reduction, or elimination, of costly and time-consuming procedures, such as human and animal testing and trial-and-error screening in vivo, it was important to correlate the findings of the in vitro ranking metric with direct in vivo skin barrier measurements. For this purpose, in vivo soap chamber measurements, including transepidermal water loss, visual skin dryness, and chromameter erythema measurements, were carried out on human volunteers using the aqueous surfactant-humectant solutions described above. The results of these in vivo measurements were found to be consistent with the ranking results obtained using the in vitro ranking metric. To further explore the validity of our model and to verify the skin barrier mitigating effect of glycerol, in vivo soap chamber measurements were carried out for aqueous SDS solutions containing 10 wt% added glycerol. These in vivo measurements support our recent in vitro finding that glycerol reduces the average radius and the pore number density of the skin aqueous pores, such that SDS micelles are hindered from penetrating into the skin and inducing skin barrier perturbation.
Synopsis
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 × 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.
The human skin barrier which serves to maintain the physiological water homeostasis of the body system is presently at focus of interest to dermatologists and pharmacologists in the light of transepidermal drug delivery. In this paper current models for the human skin barrier are reviewed in relation to present day status of lipid structure research. It is demonstrated that the barrier function as well as the partial break down of the barrier by penetration enhancers can be explained from the fact that a substantial part of the barrier lipids are in a crystalline state as opposed to the liquid crystalline state of common cell membranes.
Many skin diseases are associated with the symptom of dry skin. This effect may be due to a decreased water content in the horny layer and/or a reduced capacity to bind water. Among the natural moisturizing factors, urea has proved one of the most effective substances in the topical therapy of dry skin and to enhance both the hygroscopicity and the waterbinding capacity of the horny layer. We studied the influence of urea in various vehicles on this mechanism. Corresponding to the differences concerning the penetration of urea depending on the vehicle used, we observed differences with regard to its therapeutic effect, i.e., the increase of both hydration and waterbinding capacity of the horny layer.
Within two experimental groups of 11 and 12 people, respectively, a number of dermatological basis ointments were applied to the skin; the transepidermal water loss was monitored over the time. The readings after 5 min. allow the assumption that the applied w/o-emulsions (wool wax alcohol ointment DAB 10 with 15% and 50% water, respectively) released water onto the skin and are instable. No remarkable water liberation was found, however, out of the tested o/w-emulsion with the low water content (hydrophilic ointment DAB 10 with 50% water). This system seems to be stable on the skin. An amphiphilic-emulsion (Basic Cream DAC 1986) shows a similar performance to the w/o-emulsions tested. As expected, a distinct water release was found for a liquid o/w-emulsion with high water content, a Multilayer-system with a watery outer phase, and - to a lower extent - a Cold Cream with low water content. During the course of the measurements it became obvious that Vaselinum album DAB 10 in no way blocks the transepidermal water loss completely, but reduces it significantly. The occlusivity of the other preparations was significantly lower, with the exception of the low-water w/o-emulsion.
The influence of a monotherapy with glycerol and urea, respectively, on the stratum corneum hydration against exsiccation by a tenside solution and on the skin-smoothing effect was investigated in comparison with a combination therapy with glycerol and urea. Here, an increase of 5% in the dose of urea in an oil-in-water-emulsion did not produce significant advantages with regard to the stratum corneum hydration and the protective effect against the dehydration by tenside solutions. In contrast to this an increase in the dose of glycerol of over 5% in an oil-in-water-emulsion proved to be efficient under both criteria. With regard to the stratum corneum hydration and the protective effect against exsiccation by tendides, the combination of 5% glycerin and 5% urea was superior to a monotherapy, with exception of the oil-in-water-emulsion containing 10% glycerin. With regard to the smoothing effect only the combination of 5% urea and 5% glycerin produced a significant advantage.
Friction, electrical impedance and profilometry studies were undertaken to assess the effects of water, glycerol, mineral oil, shaving foams and talc on skin. The coefficient of dynamic friction for dry skin against a steel probe was 0.2. The effect of water alone was to increase it to 0.7 for several minutes, whereas glycerol alone, and in aqueous solutions, caused an increase to 0.7 for several hours. Mineral oil by itself gave a small, persistent increase, while water-in-oil emulsions increased the friction for about one hour. Shaving foams gave a value of about 0.5 which is consistent with the notion of a 'lubricated water' effect. Talc reduced friction on moist skin to a value close to that of dry skin. A good correlation between friction, phase delay and profilometry was found. All three measuring systems showed that water treatment lasted less than ten minutes, whereas glycerol treatments lasted many hours. None registered a large effect for mineral oil.
A comparison between two commercially available electrical methods for measurement of skin hydration, the Skicon 100® and the Corneometer CM 420®, was performed. Increased or decreased hydration state of stratum corneum was induced by patch testing with different irritants (sodium laurylsulphate and nonanoic acid) and measurement of hydration state was performed on 140 patch test reactions. It is concluded that the Skicon 100® is most sensitive for grading the hydration state of wet eczema, while the Corneometer CM 420® is most sensitive for grading the hydration state of dry eczema. The methods are complementary to one another and both methods are helpful for measuring the hydration state of the superficial epidermis.
Background/aims: The hydrating properties of three moisturising preparations, commonly recommended for the treatment of dry skin, were compared by utilising non-invasive measuring methods.
Methods: The preparations were Decubal®/Abitima® cream, Dumex Ltd; pH5-Eucerin® ointment, Beiersdorf; and Essex® cream, Schering Plough. Skicon-200® and a Corneometer CM 420® were used for assessment of skin hydration. Readings of the transepidermal water loss (TEWL) and skin temperature were also taken. The study was conducted in 2 parts, each with 12 women. The preparations were applied to a designated area on the forearms 2× a day for 7 days; the 4th, untreated, area served as control. Readings were taken before the start of treatment and every morning during the treatment period and the following week.
Results: Both electrical measuring methods showed that hydration of the stratum corneum increased after a few days of treatment, especially after the application of Decubal®/Abitima®. TEWL was not affected by any of the treatments.
Conclusions: The two electrical methods ranked the products consistently, i.e. Decubal®/Abitima® >pH5-Eucerin® >Essex®. Conductance (Skicon-200) was more discriminative than capacitance (Corneometer CM420). However, these methods are not water specific. TEWL was not affected by the treatments.
Background/aims: The cutometer is an instrument that measures mechanical properties of skin. The NOVA dermal phase meter (DPM) measures the stratum corneum (SC) hydration level. The objectives of this study were to determine which parameters of the cutometer data curves were most sensitive to changes in SC hydration level, and to determine if lowering the skin stress applied by the cutometer would increase the instrument's sensitivity to SC hydration.
Methods: In two studies, the volar forearms of ten and six subjects, respectively, were hydrated with wet paper towels for ten min. Measurements were made with the cutometer at various vacuum levels, and with the DPM. In another study, leg skin of nine subjects was hydrated by applying moisturizing lotions for 2 weeks. Measurements were made with the cutometer and DPM.
Results/conclusion: Significant changes in DPM and cutometer measurements were found after hydrating skin in each study. However, only three correlations were found between cutometer data and DPM data. The lack of correlation was perhaps due to the differences in the depth into the skin which the two instruments measure. It is not clear which cutometer data parameters are generally most sensitive to hydration level, since different parameters were found to be most sensitive in each of the three studies. Finally, lowering the cutometer vacuum level generally did not increase the sensitivity of the measurements to changes in hydration levels.
The Dermal Torque Meter® (DTM) and the Cutometer® are instruments that measure mechanical properties of skin. The NOVA(tm) Dermal Phase Meter® (DPM) measures the stratum corneum (SC) hydration level. The objectives of this study were to determine which parameters of the DTM data curves were most sensitive to changes in SC hydration level, which of the two instruments (Cutometer or DTM) was most sensitive, and what correlations existed between the Cutometer and DTM data.
Dry leg skin was created on nine subjects by washing with soap and using no moisturizers for one week. The skin was then treated with moisturizing lotions for two weeks. Measurements were made with the Cutometer, DTM, and DPM pre- and post-treatment.
Significant changes in DPM, DTM, and Cutometer measurements were found after the moisturizer treatment. However, correlations were not found between mechanical property data and DPM data. The DTM had the two parameters with the highest sensitivity of all of the DTM and Cutometer parameters. Finally, correlations between the two instruments existed for only three of the ten parameters investigated.
While measurements with all three instruments significantly changed in response to skin hydration, neither the DTM nor Cutometer data tended to correlate with DPM data, perhaps due to the differences in the depths into the skin which each instrument measures. Furthermore, the mechanical properties measured by the two instruments do not correlate well between the instruments. Finally, the DTM was found to have the most sensitive parameters.
Synopsis
Topically applied water, occlusion and topically applied glycerol were used to investigate and characterize some of the changes which occur in the hydrated stratum corneum. The effects of these treatments were monitored using non‐invasive techniques under controlled conditions.
The Servomed Evaporimeter was used to determine natural water flux from the skin surface before and after treatment. The performance of the Evaporimeter in this type of study had previously been improved by attaching a paper baffle to the detector. This eliminated the variance in output caused by atmospheric movement. Experiments were carried out at temperatures below the threshold of thermal sweating and emotional sweating was minimized.
Skin surface topography was characterized by means of a new type of profilometer. The instrument's design allowed a diamond stylus to traverse the living skin surface without significantly altering its structure. Changes in skin surface roughness were further elucidated using scanning electron microscopy and macrophotography.
In vivo penetration of glycerol was assessed by chemical analysis of stratum corneum layers of treated skin. Samples were obtained by sequential stripping of the stratum corneum using adhesive tape.
Topically applied water produced only a transient benefit because of rapid evaporation. More prolonged hydration was achieved by suppressing transepidermal water loss with polyethylene film. This occlusive hyperhydration was characterized by a significant reduction in profile roughness and by a smoother macroscopic appearance.
Glycerol achieved the same effects by reducing the magnitude of the natural water flux from the skin surface and by reducing the rate of evaporation of water from applied aqueous glycerol solution or cosmetic product. Both effects were seen as the result of lowered water activity in the proximity of glycerol.
Smoothing effects of glycerol on the skin surface, and improved appearance, persisted for at least 24 h. This persistence was explained by evidence for diffusion of glycerol into the stratum corneum where it formed a reservoir.
Hydration of the skin is known to affect its barrier function and thereby exert a profound effect on penetration of both lipophilic and hydrophilic molecules. Clinically, this effect may be achieved using liberal applications of occlusive petroleum jelly and ointments. The results presented in this paper suggest that the use of humectants could achieve useful hydration using cosmetically acceptable materials.
The biophysical properties of non-eczematous skin at three locations in atopics and non-atopics were characterized using non-invasive physical methods. Skin friction was measured with a newly developed sliding friction instrument, the degree of hydration with a capacitance meter (Corneometer CM 820), and the transepidermal water loss (TEWL) was determined using an Evaporimeter EP1. The areas examined (dorsum of the hand, volar forearm and lower back) showed lower values of friction and capacitance in the atopic patients than did corresponding sites in the normal controls. In most areas a significant correlation between friction and capacitance was found. The TEWL was increased in atopic skin, but TEWL seems to correlate neither to friction nor to capacitance.
The possible relationship between skin capacitance and the mechanical properties of the skin was studied using non-invasive techniques. Skin hydration was changed by soaking skin with tap water. Hydration of the skin increased the capacitance significantly (p less than 0.01) and hysteresis (creeping phenomenon) (p less than 0.01). The elasticity of the skin was reduced by hydration (p less than 0.01). Capacitance was found to be a poor predictor of the mechanical properties of untreated skin; while increases in hysteresis (creeping phenomenon) and decreases in elasticity were significantly (p less than 0.0001) related to changes in the capacitance of hydrated skin.
Appropriate monitoring of skin hydration during clinical and/or experimental trials needs devices with acceptable reproducibility and sensitivity under conditions ranging from increased, and normal to low hydration. The aim of this study was to compare the variation of electrometric data generated by 4 different instruments (Skicon Hygrometer, 2 CM420 and a CM820 corneometer) in normal and experimentally damaged skin displaying surface roughness. Rough skin sites were observed during the healing process after repeated tape stripping of stratum corneum in humans (e.g. 10-14 days after insult). They displayed lower conductance and or capacitance levels as compared to normal skin sites of the same subjects. The Skicon hygrometer showed higher variability as compared to the corneometers and was less sensitive, in relative terms, in the rough skin sites. This device also showed a moderate zero drift and re-zeroing was repeatedly utilized during the experiment. When the corneometer data were plotted against the hygrometer data, the slope of the regression line generated by the CM420a was different from CM420b and from CM820; the two latter were not significantly different from each other. Hence, comparison of absolute data obtained under comparable conditions (in this case CM420a and CM420b) in a single laboratory should not be made without prior calibration. Standards for evaluating interinstrumental variation are currently unavailable. This aspect of the measurement of electrical properties of the skin has not been investigated in great detail and has often been neglected in the past. Our findings also indicate that a constant control over the performances of a particular device should further improve the reliability of the data.
Differences in the dynamic skin friction coefficients (mu) were investigated with respect to age, sex, and anatomical region. A total of 29 volunteers consisting of seven young females, seven old females, seven young males, and eight old males participated in the study. Measurements were obtained from II anatomical regions, namely, the forehead, upper arm, volar and dorsal forearm, postauricular, palm, abdomen, upper and lower back, thigh, and ankle. The friction data were compared with stratum corneum hydration and transepidermal water loss (TEWL). The dynamic friction coefficient did not vary significantly between age and sex groups but varied considerably among the anatomical regions of the body. The forehead and postauricular had the highest mu (0.34 +/- 0.02) while the abdomen had the lowest (0.12 +/- 0.01); the remaining regions had an average mu value of 0.21 +/- 0.01. Similarly, no sex differences were observed for TEWL and stratum corneum hydration. Capacitance was only significantly lower on the palms of the elderly. Regional differences showed a higher state of hydration on the forehead and postauricular as well as the upper arm, upper and lower back when compared with the volar forearm. TEWL was generally lower in the elderly on all anatomical regions except the postauricular and palm. A significant correlation was established between mu and capacitance for most regions. Between mu and TEWL significant correlation was observed only on the palm and thigh. These findings suggest that frictional properties of skin are dependent on more than water content or non-apparent sweating and the role of sebum secretion is suggested as one possible factor.
The dynamic friction coefficient between skin and a Teflon probe and its correlation with age, body weight, height, transepidermal water loss and skin capacitance was studied in vulvar and forearm skin of 44 healthy female volunteers. The friction coefficient of vulvar skin was 0.66 +/- 0.03 (mean +/- SEM) compared to that of forearm skin of 0.48 +/- 0.01. The difference was highly significant (p less than 0.001). Multiple-regression analysis showed that the vulvar skin friction coefficient was significantly correlated with capacitance as an indicator of stratum corneum hydration (p less than 0.01) but not with age, weight, height or transepidermal water loss. It is concluded that the high friction coefficient of vulvar skin may be due to the increased hydration of vulvar skin. Age-related differences seem to exist for transepidermal water loss and friction coefficient in forearm but not in vulvar skin.
Experiments on skin moisture, i.e. the hydration state of the outer epidermis, were undertaken using three different types of equipment, i.e. the Skicon-100 and Corneometer CM 420 hydrometers and the Servo Med EPI evaporimeter. The studies included 10 healthy volunteers. Water was applied to test sites on the forearm and the palm of the hand, and effects monitored by the three methods. Parallel increases in conductance, capacitance and transepidermal water loss were registered for a duration of about 5 min. The Skicon-100 was more sensitive for measurement of increased hydration, while the Corneometer CM 420 might be more sensitive for measurement of decreased hydration. Inter- and intra-individual variations were minor with all instruments. According to reproducibility studies, the Corneometer CM 420 was more accurate than the Skicon-100. Technical experiments indicated that the Corneometer CM 420 depicts changes of hydration down to a depth of 0.1 mm, while the Skicon-100 measures very superficially. In conclusion, both hydrometers were deemed relevant and valid for assessment of skin moisture. The methods are complementary, and their combined use is recommended.
The basis of urea effects on human skin is its penetration into different skin layers. A strong vehicle dependence can be proved. On the basis of different penetration kinetics of urea from O/W and W/O emulsions, various efficiencies can be deduced with regard to the penetration promotion of drugs or the increase of the water-binding capacity of the horny layer. The significance of these findings for the use of urea in external therapy for stabilization and construction of a normal functional structure of the horny layer is discussed. By altering the functional structure of the horny layer and considerable increase of drug liberation from ointment bases urea is one of the most effective penetration promoters. An increased penetration rat of some corticosteroids and dithranol from urea containing ointment could be demonstrated in human skin. The resulting penetration promotes two possible applications in topical therapy: an increased therapeutic effect for a given concentration of the active constituent: a given therapeutic effect could be obtained with a reduced concentration for the active ingredient.
Based on the evidence from previous studies that the hydration state of the skin surface can be evaluated quickly and quantitatively in terms of conductance to the high frequency electric current of 3.5 MHz, a simple in vivo function test has been established that furnishes information on the hygroscopic property and water-holding capacity of the stratum corneum in a few minutes. The test procedure consists of electromeasurements before and after application of a droplet of water on the skin for 10 seconds to obtain data on the hygroscopic property of the skin surface and later serial measurements at an interval of 30 seconds for 2 minutes to evaluate the water-holding capacity. Under usual ambient conditions normal skin surface showed a high rise in conductance just after application of water, which was followed by a rapid fall-off within 30 seconds, thereafter by gradual return to the pregydration levels by 2 min.
By this method we have demonstrated that (i) the superficial horny layer of normal skin is much less hygroscopic and less capable of holding water than te corresponding deeper portions and that (ii) scaly skin shows functional defects in both hygroscopicity and water-holding capacity, between which the former normalizes much faster than the latter.
Moisturizers are known to have occlusive, emollient and humectant properties, all of which help to alleviate the symptoms of skin xerosis. Although the biological mode of action of moisturizers is poorly understood, the recent observation that skin xerosis is associated with incomplete desmosome digestion suggests that moisturizers improve the desquamation process in such conditions. To examine the possibility that certain moisturizers act by facilitating desmosomal digestion, we investigated the ability of glycerol, a common humectant, to influence this process in stratum corneum in vitro. Examining desmosome morphology in isolated stratum corneum by electron microscopy, it was observed that the desmosomes were in more advanced stages of degradation in glycerol-treated tissue compared with control tissue. This enhanced desmosomal degradation in glycerol-treated tissue was confirmed by significant decreases in the levels of immunoreactive desmoglein 1, a marker of desmosome integrity. Desmosomal degradation was also shown to be a humidity-dependent event, being significantly reduced at low relative humidity. The effect of glycerol on desmosome digestion was emphasized further in two in vitro model systems. Firstly, glycerol increased the rate of corneocyte loss from the superficial surface of human skin biopsies in a simple desquamation assay. Secondly, measurement of the mechanical strength of sheets of stratum corneum, using an extensiometer, indicated a dramatic reduction in the intercorneocyte forces following glycerol treatment. These studies demonstrated the ability of glycerol to facilitate desmosome digestion in vitro. Extrapolating from these results, we believe that one of the major actions of moisturizers in vivo is to aid the digestion of desmosomes which are abnormally retained in the superficial layers of xerotic stratum corneum.
Two commercially available electrical instruments which evaluate the hydration state of the skin surface were compared in in vitro and in vivo experiments. The skin surface hygrometer (Skicon-200) employs high-frequency conductance, whereas the corneometer (CM 420, CM 820) uses electrical capacitance to determine the level of hydration. In a simulation model of in vivo stratum corneum (SC), the high frequency conductance device showed a much closer correlation with the hydration state of the surface SC (r = 0.99) than the capacitance device (r = 0.79), suggesting that the former can accurately assess the hydration dynamics of SC, particularly that due to the accumulation of easily releasable secondary bound water and free water. Both devices were insensitive to changes of hydration taking place in deeper viable skin tissues, e.g. the accumulated tissue fluids in suction blisters. Although the capacitance device correlated poorly with the hydration dynamics in normal SC, its sensitivity to changes occurring in extremely dry skin, such as scaly psoriatic lesions, suggests its measurements characteristics at an extremely low state of hydration, consisting of mostly bound water, such as noted in pathologic SC.
Moisturizers and emollients do not only smooth the skin but also make it more supple. To clarify this effect, the short-term influence of tap water, paraffin oil, ethanol and glycerin on skin mechanics was studied. These substances are all common ingredients in moisturizers and emollients. Significant changes were seen already after 10 min of application. The distensibility and hysteresis (creep phenomenon) showed the most pronounced changes. Water and paraffin oil application caused significant (p < 0.03) increases after 10 min of application. The changes persisted for at least 10 min following paraffin oil application, while they disappeared sooner following water application. Application of ethanol had a negative effect on distensibility (p < 0.03). Glycerin appears to have a slow onset of action, but with the changes continuing even after application was stopped. The changes induced by glycerin appear to be similar to those induced by water and paraffin oil. The study shows that some of the most common ingredients in moisturizers and emollients are capable of inducing significant changes in the mechanical properties of human skin in vivo even after a 10-min application, suggesting that the outermost layers of the epidermis play an important role in skin mechanics.
Bioengineering of the skin: methods and instrumentation
- F Distante
- E Berardesca
- Hydration Berardesca E
- Wilhelm P Kp Elsner
- Maibach
- Hi
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The effect of 3 moisturisers on skin surface hydration, electrical conductance (Skicon-200), capacitance (Corneometer CM 420), and transepidermal water loss (TEWL)
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