Prediction and measurement of surfactant action upon human skin under realistic conditions

The lysosomal enzyme acid phosphatase has been characterized and quantified in tapestrip biopsies of human stratum corneum by means of a sensitive spectrofluorometric procedure. When the stratum corneum of panellists was exposed to dilute solutions of various surfactants under realistic exposure conditions, the changes observed in stratum corneum acid phosphatase specific activity have been found to correlate very closely with the visual, macroscopic changes such as dryness and flakiness, that are elicited in skin as a result of surfactants. This method monitors denaturation of stratum corneum proteins, which is an important feature of skin surfactant interactions, and serves as an effective, non-invasive predictive tool for skin irritancy and mildness of surfactants.
Prevention et mesure de l'action des tensio-actifs sur la peau humaine dans des conditions conformes a la réalité     

荞麦精粉中的黄酮及其自由基清除活性

对 5种不同来源的荞麦Astra、Hruszowska、LeHarpe、Lileja及Prego的黄酮物质进行了研究。光谱分析表明Astra、Hruszowska、LeHarpe、Lileja和Prego精粉中总的抗氧化剂含量分别为 14 6、2 1 4、13 8、16 0和 11 4mg/ 10 0 g ;反相高效液相色谱分析说明 ,除了荞麦中最重要的芦丁以外 ,Astra中有白藜芦醇、原儿茶酸和儿茶素 ;Hruszowska中有原儿茶酸和儿茶素 ;LeHarpe中有白藜芦醇、原儿茶酸和儿茶素 ;Lileja中有白藜芦醇和儿茶素 ;Prego中有儿茶素和白藜芦醇。精粉中芦丁的含量按品种名称字母顺序依次为 5 6、3 8,10 1、6 3和 4 9mg/ 10 0 g。进一步的细胞培养实验揭示 ,荞麦精粉醇提物能有效地防止自由基引发的氧化反应 ,Astra和Hruszowska提取物的作用特别明显。     

Control of melanosome transfer by promoting shrinkage or expansion of melanocyte dendrites

Coenzyme Q₁₀ is an endogenous antioxidant found in the skin along with vitamins A, C and E. Coenzyme Q₁₀ is used increasingly in cosmetic products and is advertised as a skin energizer, protector against skin aging, skin repairer and an anti-wrinkling agent. As the outermost layer of skin, the stratum corneum is the interface between the body and the environment and requires antioxidants to protect it and the epidermis and dermis below it. Nutrient levels in the stratum corneum correlate with those in the skin. Two forms of coenzyme Q₁₀ (pure coenzyme Q₁₀ and a yeast-based coenzyme Q₁₀) were investigated in a commercial vehicle. Two groups of subjects were tested aged 21–29 and 51–70, respectively. Coenzyme Q₁₀ absorption in the stratum corneum was determined after a 1-h application and ethanol extraction. Significantly more yeast coenzyme Q₁₀ was absorbed than the pure coenzyme Q₁₀ and the middle-aged subjects absorbed about twice as much coenzyme Q₁₀ as did the younger subjects. Skin antioxidants were significantly increased by yeast coenzyme Q₁₀ but not by pure coenzyme Q₁₀. Peroxides declined in the stratum corneum after twice daily application of coenzyme Q₁₀ with both forms but the decrease was greater with the yeast form. The older subjects had significantly higher baseline levels of lipid peroxides than did the younger group, indicating an increase in skin oxidative damage with age. The yeast coenzyme Q₁₀ is the superior form of coenzyme Q₁₀ for human skin application.     

Synthesis of new antioxidant conjugates and their in vitro hydrolysis with Stratum corneum enzymes

The aim of this study was to synthesize new precursors, combinations of well-known antioxidant molecules: resveratrol, lipoic acid and vitamin E to improve their photo-stability and to modulate their lipophylic character. Active antioxidants are available through a controlled release by the action of skin enzymes upon a topic application. Two conjugates are described, the combinations of resveratrol-lipoic acid (6) and resveratrol-vitamin E (10). Both compounds are new molecules. This work describes their synthesis, characterization, stability study and in vitro biohydrolysis. Stratum corneum enzymes efficiently hydrolysed in vitro precursor 6 and liberate both active molecules, resveratrol and lipoic acid over the period of 72 h. Precursor 10 was hydrolysed in vitro by combination of Stratum corneum enzymes and the cholesterol esterase. A simple technique of preparation of the human Stratum corneum hydrolases is also described.     

Vol. 42, No. 1, pp.16-21, 2008Decrease in the skin transparency induced by protein carbonylation in the stratum corneum

It has been reported in recent years that the carbonyl modification of protein plays a part in various diseases. The existence of the protein carbonylation in the stratum corneum also came to be known in the last few years, but the effect on the properties of the stratum corneum including the skin appearance was not clarified. In this study, we examined the influence of protein carbonylation in the stratum corneum to provide helpful information for skin care products focusing on transparency of the stratum corneum. Firstly, we developed a method to assess the protein carbonylation level numerically by the image analysis of tape-stripped stratum corneum reacted with a fluorescent hydrazide. The level of stratum corneum carbonylation of the sun-exposed site (face) was higher than that of unexposed site (upper arm), and the surface part of the stratum corneum showed a higher level of carbonylation compared with the deeper layer. Stratum corneum carbonylation was induced by in vitro UV irradiation. In addition, it was shown that the skin transparency score was significantly low in the woman with high level of protein carbonylation in the stratum corneum of the cheek. An experimentally carbonylated stratum corneum sheet in vitro became opaque. Among the amino acids investigated, L-lysine was the most effective to prevent carbonylation of the stratum corneum ex vivo . Moreover, L-lysine inhibited the decrease in the skin transparency caused by experimental carbonylation of the stratum corneum in the human skin. These results suggest that preventing the carbonylation of the stratum corneum due to adverse effects from the environment by l-lysine could improve the skin transparency.
Keywords: stratum corneum, protein carbonylation, appearance, skin transparency, l-lysine, amino acids, fluorescent hydrazide, tape-stripping     

Infrared spectroscopy of the skin: influencing the stratum corneum with cosmetic products

The stratum corneum is the outermost layer of the skin and, as such, represents the decisive barrier between the body and the environment. The combination of horny cells and lamellar lipid layers prevents water loss from the body and protects it against penetration by exogenous substances. For selective investigation of the thin outermost stratum corneum layer ATR-FTIR (attenuated total reflection Fourier transform infrared) spectroscopy has proved itself in practice. It provides information about the sebum content, type of fatty substances, water content and degree of order of the lamellar lipid film in the stratum corneum. Different types of skin (dry, normal and greasy) differ mainly in their sebum content but also in the composition of their fats and the degree of order of their lipids. A comparison with model lipid mixtures shows that the stratum corneum lipids are mainly present in a fixed gel form under physiological conditions. In cleansing processes a large part of the sebum is removed from the skin. The skin reacts to the defatting process by the rapid secretion of sebum. After cleansing with a mild face cleansing emulsion the re-achievement of the same fat status takes longer than with a surfactant shower gel. Skin creams cause alterations to the skin moisture and in the degree of order of the stratum corneum lipids. A lamellar cream with a structure similar to that of the stratum corneum lipids increases the degree of order of the alkyl chains of the skin lipid film (biomimetic principle), whereas a conventional w/o cream reduces this degree of order. Skin moisture increases after the use of the creams.     

Assessment of human stratum corneum thickness and its barrier properties by in-vivo confocal Raman spectroscopy

IFSCC Magazine , 12 (2009) (1) 9–15
Measurement of water concentration profiles across living human skin by confocal Raman spectroscopy has developed into a powerful tool for a better understanding of distribution and function of water in the epidermis. From the water profile across the epidermis the border between stratum corneum and stratum granulosum can be estimated. This is due to the steep drop in water concentration from the inner to the outer side of the stratum corneum. Water content drops from approximately 70% at the inner stratum corneum to only 30% at the skin surface. This slope of the curve becomes clearly flatter in the stratum granulosum. A second parameter is usually taken from confocal Raman spectroscopy to define the stratum corneum border. This is the content of natural moisturization factor (NMF), which should be present only in the stratum corneum. Located at the depth at which the NMF content levels off and the slope of the water profile curve changes is the stratum corneum border. The goal of this work was to develop stratum corneum thickness detection into a robust and semi-automated measurement relying only on the water profile. Further, the aim was to base the empirical findings of water distribution in the epidermis on a well established theory, Fick's law of diffusion. A mathematical model was developed to fit the water profile curve for a robust and automated detection of the stratum corneum border. In addition, the new model automatically resulted in an accurately determined slope of the water concentration curve in the stratum corneum. This slope, or more exactly the gradient, is one of two parameters directly related to transepidermal water transport across the stratum corneum.
Keywords:  Barrier function, Fick's law, Raman spectroscopy, stratum corneum, transepidermal water loss     

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.     

Evolution of lipid composition in skin treated with blackcurrant seed oil

This report utilizes a new procedure based on epidermal stripping to analyse unlabelled skin fatty acids. This technique was applied to the study of human dry skin treated with blackcurrant seed oil, an essential fatty acid rich lipid also containing γ linolenic acid.
In human dry skin the usual fatty acids were found in the stratum corneum as in normal skin outer layers. Among the saturated series no significant difference was observed in the C16 chain but a smaller quantity of C18:0 was detected. In the unsaturated series a marked fall of linoleic acid as well as a higher level of C16:1 in the stratum corneum appeared as the major significant events that could characterize dry skin. γ linolenic acid was detectable neither in normal nor in dry skin. α linolenic acid was found but not consistently.
After multiple applications of blackcurrant seed oil in an emulsion preparation, impregnation of the stratum corneum was complete, and essential or other fatty acids contained in the oil (particularly linoleic and linolenic acids) were found in combination with endogenous lipids. Possibly they contribute to enhance the protective effect of the stratum corneum.     

Skin lipid organization,composition and barrier function

Citation: IFSCC Magazine, 10 (2007) (4) 297–307 The primary function of the skin is to act as a barrier against unwanted influences from the environment and to protect the body from water loss. The barrier function of the skin is located in the superficial layer of the skin, the stratum corneum. The stratum corneum consists of dead cells filled with keratin and water, the corneocytes, embedded in lipid regions. As the lipid regions are the only continuous structure in the stratum corneum, they are considered to be very important for the skin barrier function. The main lipid classes are ceramides, cholesterol and free fatty acids. In this paper the lipid organization in human stratum corneum is reviewed. In addition, the role the various lipid classes play in lipid organization is discussed using mixtures prepared from either native human ceramides or synthetic ceramides. Finally, a model is described which allows study of the relation between lipid composition, organization and barrier function. This model is referred to as the stratum corneum substitute. Keywords: ceramides, FTIR, lipid organization, stratum corneum, X‐ray diffraction     

Non-invasive assessment of stratum corneum structure and function

Methods for the study of the stratum corneum in situ are described and their application to clinical problems and cosmetic science are discussed. In vivo measurements of the thickness of skin and the components of skin can be made using high frequency pulsed ultrasound. Improved resolution of the device should allow measurement of epidermal thickness, and even that of the stratum corneum, which may vary with hydration. The protective ability of the stratum corneum can be estimated in a number of ways, the most familiar technique being transepidermal water loss measurements. Mechanical properties of the stratum corneum have been widely investigated in vivo by numerous researchers. A recent technique devised by us to deform the stratum corneum using an extendable metal frame has been used on patients with ichthyotic disorders. The deformation or compliance of the skin surface has been measured using profilometric methods, and compared to normal individuals. The results appear to be in agreement with the loss of flexural ability experienced by ichthyotic patients. Other mechanical methods more usually involve the measurement of the forces generated by skin while undergoing extension. Three techniques are described which have been used to investigate hydrational change with emollient application. Finally, the phenomenon of desquamation is discussed and methods presented for its evaluation. Passive collection of corneocytes using chambers is useful for estimation of the rates of desquamation, but are laborious and inconvenient. Forced desquamation using the desquamator enables rapid controlled harvesting of corneocytes. In addition to this, the dansyl chloride fluorescence technique has been adopted for estimation of stratum corneum kinetics using visual comparison and fluorimetric techniques. These techniques require further refinement and validation, but the tests available now are nonetheless important in understanding the biology and pharmacology of the stratum corneum.     

Water retention of treated stratum corneum measured by a coupling method: thermal desorption-mass spectrometry

A thermal desorption autosampler coupled to a mass spectrometer has been used to measure the in vitro water retention of human stratum corneum as a function of treatment applied. Samples were treated with ingredients possessing good hygroscopic properties which are used in the formulation of moisturizing creams. After being treated, stratum corneum samples were dried and rehydrated and then analysed. The paper describes the method used to quantify their hygroscopic capacity in terms of the percentage of water retained. Ten humectants were examined, of which urea, glycerine, ammonium lactate and a new salt of an α-hydroxy acid were found to have the highest activities. This method can also be used to quantify the water retention capacity of various types of pathological skin such as ichthyosis and psoriasis.     

Trends in stratum corneum research and the management of dry skin conditions

The structure, composition, formation and function of the stratum corneum have been the subject of intense research over the last few decades. As has become apparent, stratum corneum barrier function is not only dependent on one single component but also on its total architecture. Recent developments in understanding lipid composition have led to a new ceramide nomenclature system, a new proposal for a molecular model of the interactions between ceramides, cholesterol and fatty acids, and the demonstration of the presence of crystalline orthorhombic and gel hexagonal lipid phases in the stratum corneum. Linoleate-containing ceramide one, now known as CER EOS, have been shown to be essential for the formation of the 13 nm long periodicity phase (LPP) observed by electron microscopy and X-ray diffraction studies, whereas long-chain fatty acids are important for the formation of the crystalline lipid phases essential for barrier function. The role of the corneocyte envelope, its constituent proteins and its transglutaminase-mediated maturation processes have been shown to be essential for good skin condition. Several proteases may have a role in corneodesmolysis, particularly serine and cathepsin-like enzymes. Novel filaggrin polymorphisms have been identified that may be involved in the expression of a dry skin phenotype. Disturbances in lipid packing states, reduction in ceramide levels (particularly the phytosphingosine-containing ceramides), reductions in the levels of long-chain fatty acids and loss of the LPP largely account for the perturbations in lipid structure that occur in dry skin. The reduced corneodesmolysis that occurs in this xerotic skin disorder is now well accepted and is caused by reductions in the levels and activities of stratum corneum proteases together with elevated levels of corneodesmosomal glycoproteins in the superficial layers of the stratum corneum. Additionally, increased levels of fragile corneocytes are associated with reduced transglutaminase activity and corneocyte envelope cross-linking events. However, in comparison with the advances in our understanding of the textural changes that occur in dry skin, the somatosensory changes are poorly understood and the itching associated with dry skin is still an under-researched area. The unique biosensor role of the stratum corneum essential for a competent natural moisturizing barrier may also have a role to play in the action of anti-ageing technologies by controlling the expression and secretion of epidermal cytokines and growth factors. Technologies to treat the surface textural skin problems, enhance the differentiation process, particularly lipid biosynthesis, and to control the somatosensory problems in dry skin have received much attention in the last decade. This paper will review the state of the art of stratum corneum biology and the trends in the management of dry skin.     

In vitro bio-accessibility and antioxidant activity of grape polyphenols

The bio-accessibility (the release of compounds from solid food matrices) of grape polyphenols using an in vitro model simulating gastro-intestinal conditions has been investigated. In vitro studies are needed to unravel factors affecting the release of antioxidants during digestion. The amount of bio-accessible polyphenols, flavonoids and anthocyanins increases during gastric digestion. The transition in the intestinal environment causes a decrease in all the analyzed classes of polyphenols followed by a renewal in the extraction of polyphenols and flavonoids but not of anthocyanins. The stability under gastro-intestinal conditions of pure phenolic acids, flavonoids and resveratrol has been analysed. Gastric digestion had no effect on any phenolic tested. Phenolic acids and resveratrol were degraded under pancreatic conditions whereas catechin and quercetin were not. Changes in antioxidant activity during digestion were correlated to the changes in polyphenols concentration as well as to the pH. Our results suggest that the gastro-intestinal tract may act as an extractor where polyphenols are progressively released from solid matrix and made available for the absorption or to exert their biological effects in the gastro-intestinal tract.     

A liquid crystal application in skin care cosmetics

Intercellular lipids of the stratum corneum contribute threefold to the maintenance of a healthy skin: by hydration, cell adhesion, and reduction of transepidermal water loss. All of these functions can be attributed to the self-organizing property of the amphiphilic molecules of the stratum corneum lipids. A new type of skin care product called Lamellar Gel was developed, which contains a (synthesized) pseudo-ceramide. Its structure is similar to that of ceramide found among the stratum corneum lipids, which allows it to control intramolecular interactions. Compared to regular emulsions the Lamellar Gel demonstrated better skin care characteristics regarding permeability, skin hydration, and skin occlusion. This was attributed to the fact that it formed the same self-organizing structure as natural stratum corneum lipids, hence showing a high affinity to the skin. A high moisturizing effect was observed as the Lamellar Gel combines the benefits of both O/W and W/O emulsions: it provides the same initial hydration as an O/W emulsion and at the same time the same occlusivity as a W/O emulsion. Transepidermal water loss increases under dry environmental conditions. This especially affects the skin around the eyes, where the skin is very thin, and wrinkles are very easily formed. Treatment with the Lamellar Gel recovered these wrinkles promptly and hydrated the stratum corneum for a long time.     

Predicting skin penetration of actives from complex cosmetic formulations: an evaluation of inter formulation and inter active effects during formulation optimization for transdermal delivery

Twenty products, containing a radiolabelled form of each active in typical cosmetic formulations, were made and applied to female human epidermal membranes mounted in Franz diffusion cells for 48 h under ‘in use’ conditions. The products consisted of combinations of five formulations (a hydro‐alcoholic gel, an oil in water emulsion, a water in oil emulsion, a microemulsion and an oil) with four model drug actives (testosterone, hydrocortisone, 5‐fluorouracil and ketoconazole). Steady‐state flux appeared to be reached by 8 h and maintained for all products, other than for the microemulsions, consistent with the actives being present in the residual formulation on the skin at saturation. The recovery for each active at the end of the 48‐h study (from a series of stratum corneum tape strips, the remaining skin, cumulative amount penetrating into the receptor solution, product washed from the skin and on the donor chamber cap) ranged from 86.5% to 100.6%. The rank order of the fluxes for the actives from the hydro‐alcoholic gel is consistent with the known active molecular size and polarity determinants for maximum epidermal flux. Actives with similar steady‐state (maximum) fluxes from a range of formulations had retention in the stratum corneum and similar transport rate constants through the stratum corneum. The microemulsion formulation significantly enhanced both the stratum corneum steady‐state flux and transport rate constant for 5‐fluorouracil, hydrocortisone and testosterone. The penetration flux of each active could be related to its size and polarity and appeared maximal when the actives in the different cosmetic formulations applied to the skin under ‘in use’ conditions were likely to remain in the residual product on the skin as a saturated solution after solvent evaporation. Enhanced penetration fluxes can be achieved by formulation selection and an appropriate choice/mix of emollients/adjuvants. The principles described here provide a framework for understanding the delivery of cosmetic ingredients from various formulations.     

Electrometric assessment of the effect of a zinc oxide paste in diaper dermatitis

Diaper dermatitis affects nearly 50% of infants as well as some bed-ridden adults particularly in the elderly people. This condition is induced by irritation and maceration, and may be further exacerbated by Candida sp. colonization and infection. A key factor in the pathogenesis is the alteration in both the barrier function and the water-holding capacity of the stratum corneum. The purpose of this study was to assess the effects of an unmedicated zinc oxide–petrolatum paste and to observe for possible shielding and restoring effects on the water-holding capacity of the stratum corneum altered by diaper dermatitis. The paste appeared to load the hollow skin microrelief. It was inferred that this effect was responsible for a reticulated shielding effect. Compared with healthy skin and untreated diaper dermatitis, the application of the anhydrous paste resulted in a trend to normalize electrometric properties of skin reflecting the combination of transepidermal water loss and the water-holding capacity of the stratum corneum.     

The ultraviolet microscopic transmission characteristics of human stratum corneum

This study has evaluated the ultraviolet light transmission characteristics of human stratum corneum at the single cell level using a low light level video microscope to measure the mean percentage transmission of light at different wavelengths and the variation in transmission across the stratum corneum. Stratum corneum was isolated by an enzymic technique and examined on a low light level UV video microscope. Quantitative evaluation of the transmitted monochromatic light for the underside of the layer was measured directly using a Kontron UNIPS image processor or indirectly with a Quantimet 920 image processor after video recording. Transmission distribution histograms were obtained from samples of stratum corneum taken from human breast, scalp, abdomen and leg. Mean transmission values were also derived and compared with diffuse transmission values obtained using the same tissue mounted on an integrating sphere. The UV microscopic transmission characteristics of enzyme separated stratum corneum clearly demonstrated that this structure was not an ideal diffuser. Uniform light intensity on the surface of the stratum corneum led to areas of transmitted intensity in close proximity that differed by factors ofthree to six fold, e.g. between regions of high (>70%) and low (<20%) brightness. However, the average transmission was found to be compatible with published data obtained by diffuse transmission spectrophotometry, taking into account the enhanced transmission arising from stratum corneum immersion in phosphate buffered saline. This was confirmed by the elevated values obtained by diffuse transmission spectrophotometry in this study for samples of stratum corneum prepared for UV microscopy being higher than these found in published data. It is obvious from these findings that viable cells in the epidermis are not exposed to a uniform incident light intensity even when this is true for the surface of skin. Studies of skin response to ultraviolet light at the single cell level must take account of the possibility of preferential exposure of specific sites in any subsequent explanation of cell sensitivity. This is in addition to the already well established cell cycle dependent ultraviolet sensitivity.     

Seasonal influences on stratum corneum ceramide 1 fatty acids and the influence of topical essential fatty acids

Ceramide 1 is the main repository of stratum corneum linoleic acid, and changes in the levels of ceramide 1 linoleate are associated with cutaneous abnormalities: essential fatty acid deficiency, atopic dermatitis and acne. We have previously reported seasonal variation in stratum corneum lipids where lipids, particularly ceramides, are very much reduced in winter which probably influences the appearance of skin xerosis in this season. However, investigations into the seasonal variation in ceramide 1 fatty acid levels and the effects of topical essential fatty acids on the composition of these lipid species have not been conducted in healthy subjects. We determined the composition of stratum corneum ceramide 1 esterified fatty acids in leg skin from Caucasian women in winter and summer and also investigated the effects of topical triglycerides rich in linoleic acid on stratum corneum ceramide 1 fatty acid levels in winter. A dramatic seasonal variation was observed. Whereas decreased levels of linoleic acid and some saturated fatty acids (C-15 and C-24) were observed in the winter months, increased levels of oleic acid were found. Nevertheless, it was possible to normalize the levels of stratum corneum ceramide 1 linoleate following topical application of formulations containing linoleic acid-rich triglycerides for 4 weeks. The reduction in ceramide 1 linoleate may lead to impaired stratum corneum function and increased susceptibility to skin xerosis in winter. However, by using formulations containing linoleic acid esters it is possible to correct these changes and possibly improve barrier resilience.     

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.