Natural Moisturizing Factor Research Articles

Age related depth profiles of human Stratum Corneum barrier-related molecular parameters by confocal Raman microscopy in vivo

In this study, stratum corneum (SC) depth profiles of hydrogen bound water molecule types, intercellular lipid (ICL) ordering, concentration of natural moisturizing factor (NMF) and keratin folding/unfolding properties are investigated in vivo for older (mean 50 years old) and younger (mean 29 years old) human skin using confocal Raman microscopy.The results show that the SC of the older group is modestly thicker (p<0.1), has more hydrogen bound water molecules at the depth 10–30% of the SC thickness (p<0.05), has a higher ordered organization of ICL (p<0.1) and higher concentration of NMF (p<0.05) at the depth 20–40% of the SC thickness compared to the younger group. This study also reveals, that the hydrogen bonding state of water highly correlates with NMF and the lateral structure of ICL but not with keratin’s folding/unfolding properties.The presented results let suggest, that the decreased trans-epidermal water loss (TEWL) with increasing age cannot be sufficiently explained by only the increased SC thickness, but additionally by the increase of ICL ordering, higher NMF concentration and thus larger amount of hydrogen bound water molecules at the depth 20–40% of the SC thickness.

Probing skin physiology through the volatile footprint: Discriminating volatile emissions before and after acute barrier disruption

Volatile organic compounds emitted by human skin were sampled before and after acute barrier disruption of the volar forearm to investigate the significance of this approach to skin physiology research. A small wearable housing integrating a solid-phase micro-extraction fibre permitting rapid enclosed headspace sampling of human skin volatiles is presented, enabling non-invasive sample collection in 15minutes, in a comfortable wearable format. Gas chromatography-mass spectrometry was utilised to separate and identify the volatile metabolites. A total of 37 compounds were identified, with aldehydes (hexanal, nonanal, decanal), acids (nonanoic, decanoic, dodecanoic, tetradecanoic and pentadecanoic acids) and hydrocarbons (squalane, squalene) predominant within the chemical profile. Acute barrier disruption was achieved through tape stripping (TS) of the stratum corneum to determine the impact on the volatile signature. Principle component analysis demonstrated there to be a discriminating volatile signature before and after TS. The dysregulation of significant features was examined. Several compounds derived from sebaceous components and their oxidation products were altered following barrier disruption, including squalane, squalene, octanal and nonanal. The upregulation of glycine was also observed, which may indicate a perturbation to the skin's natural moisturising factor production. TS impacted the hydro-lipid film that functions within the skin barrier, resulting in a differing volatile signature from affected skin. This provides a valuable non-invasive approach for scientific and clinical studies in dermatology, particularly around dermatological disorders associated with compromised barrier function.

Current knowledge on biomarkers for contact sensitization and allergic contact dermatitis.

Contact sensitization is common and affects up to 20% of the general population. The clinical manifestation of contact sensitization is allergic contact dermatitis. This is a clinical expression that is sometimes difficult to distinguish from other types of dermatitis, for example irritant and atopic dermatitis. Several studies have examined the pathogenesis and severity of allergic contact dermatitis by measuring the absence or presence of various biomarkers. In this review, we provide a non-systematic overview of biomarkers that have been studied in allergic contact dermatitis. These include genetic variations and mutations, inflammatory mediators, alarmins, proteases, immunoproteomics, lipids, natural moisturizing factors, tight junctions, and antimicrobial peptides. We conclude that, despite the enormous amount of data, convincing specific biomarkers for allergic contact dermatitis are yet to be described.

Sex differences in amino acids lost via sweating could lead to differential susceptibilities to disturbances in nitrogen balance and collagen turnover

Fluid collected during sweating is enriched with amino acids derived from the skin’s natural moisturising factors and has been termed “faux” sweat. Little is known about sex differences in sweat amino acid composition or whether faux sweat amino acid losses affect nitrogen balance. Faux sweat collected by healthy adults (n = 47) after exercise, and at rest by chronic fatigue patients, was analysed for amino acid composition. Healthy females had higher total amino acid concentrations in sweat (10.5 ± 1.2 mM) compared with healthy males (6.9 ± 0.9 mM). Females had higher levels of 13 amino acids in sweat including serine, alanine and glycine. Higher hydroxyproline and proline levels suggested greater collagen turnover in females. Modelling indicated that with conservative levels of exercise, amino acid losses in females via faux sweat were triple than those predicted for urine, whereas in males they were double. It was concluded that females were more susceptible to key amino acid loss during exercise and/or hot conditions. Females reporting chronic fatigue had higher levels of methionine in faux sweat than healthy females. Males reporting chronic fatigue had higher levels of numerous amino acids in faux sweat compared to healthy males. Higher amino acid loss in faux sweat associated with chronic fatigue could contribute to a hypometabolic state. Depending on activity levels, climatic conditions and gender, amino acid losses in sweat and skin leachate could influence daily protein turnover where periods of continuously high turnover could lead to a negative net nitrogen balance.

New opportunities in the therapy of steroid-specific dermatosis - combination of topical glucocorticosteroid with urinium

External therapy with topical steroids is used for a long time. To date topical glucocorticosteroids (TGCS) are in the leading position in dermatology among all medicines for external therapy. TGCS as a powerful tool of pathogenic action can rapidly reduce or decrease inflammatory changes in the skin and eliminate subjective symptoms of dermatoses (itching, burning). their positive effect lead to the rehabilitation of working ability and daily living activity, positively affect the psychoemotional state and significantly improve the patient’s quality of life. Urea in dermatology has been used for a very long time, as it softens the skin, reduces its dryness and eliminates peeling. In recent decades interest in this compound has intensified after a formation of an idea about natural moisturizing factor (NMF) - a complex of substances (which includes urea) being a part of the intercellular matrix of the epidermis and capable of retaining the water in the epithelial layer of the skin necessary for its normal functioning. The article presents modern literature data on the reasoning of the inclusion of a combination of topical glucocorticosteroids with urea in a complex therapy of steroid-responsive dermatoses.

Effect of allergens and irritants on levels of natural moisturizing factor and corneocyte morphology.

SummaryBackgroundThe irritant sodium lauryl sulfate (SLS) is known to cause a decrease in the stratum corneum level of natural moisturizing factor (NMF), which in itself is associated with changes in corneocyte surface topography.ObjectiveTo explore this phenomenon in allergic contact dermatitis.MethodsPatch testing was performed on patients with previously positive patch test reactions to potassium dichromate (Cr), nickel sulfate (Ni), methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI), or p‐phenylenediamine. Moreover, a control (pet.) patch and an irritant (SLS) patch were applied. After 3 days, the stratum corneum from tested sites was collected, and NMF levels and corneocyte morphology, expressed as the amount of circular nanosize objects, quantified according to the Dermal Texture Index (DTI), were determined.ResultsAmong allergens, only MCI/MI reduced NMF levels significantly, as did SLS. Furthermore, only MCI/MI caused remarkable changes at the microscopic level; the corneocytes were hexagonal‐shaped with pronounced cell borders and a smoother surface. The DTI was increased after SLS exposure but not after allergen exposure.Conclusions MCI/MI significantly decreased NMF levels, similarly to SLS. The altered corneocyte morphology suggests that skin barrier damage plays a role in the pathogenesis of MCI/MI contact allergy. The DTI seems to differentiate reactions to SLS from those to the allergens tested, as SLS was the only agent that caused a DTI increase.

The effectiveness of a skin care program for the prevention of contact dermatitis in health care workers (the Healthy Hands Project): study protocol for a cluster randomized controlled trial

BackgroundHealth care workers (HCW) are at high risk for developing occupational hand dermatitis (HD) due to frequent exposure to ‘wet work’. Amongst HCWs, nurses are at highest risk, with an estimated point prevalence of HD ranging between 12 and 30%. The burden of disease is high with chronicity, sick leave, risk of unemployment and impaired quality of life. Despite evidence from the medical literature on the risk factors and the importance of skin care in the prevention of HD, in practice, compliance to skin care protocols are below 30%. New preventive strategies are obviously needed.Methods/designThis is a cluster randomized controlled trial, focusing on nurses performing wet work. In total, 20 wards are recruited to include 504 participating nurses in the study at baseline. The wards will be randomized to an intervention or a control group and followed up for 18 months.The intervention consists of the facilitation of creams being available at the wards combined with the continuous electronic monitoring of their consumption with regular feedback on skin care performance in teams of HCWs. Both the intervention and the control group receive basic education on skin protection (as ‘care as usual’). Every 6 months, participants of both groups will fill in the questionnaires regarding exposure to wet work and skin protective behavior. Furthermore, skin condition will be assessed and samples of the stratum corneum collected. The effect of the intervention will be measured by comparing the change in Hand Eczema Severity Index (HECSI score) from baseline to 12 months. The Natural Moisturizing Factor (NMF) levels, measured in the stratum corneum as an early biomarker of skin barrier damage, and the total consumption of creams per ward will be assessed as a secondary outcome.DiscussionThis trial will assess the clinical effectiveness of an intervention program to prevent hand dermatitis among health care workersTrial registrationNetherlands Trial Register (NTR), identification number NTR5564. Registered on 2 November 2015.

Lowering relative humidity level increases epidermal protein deimination and drives human filaggrin breakdown

BackgroundDeimination (also known as citrullination), the conversion of arginine in a protein to citrulline, is catalyzed by a family of enzymes called peptidylarginine deiminases (PADs). Three PADs are expressed in the epidermis, one of their targets being filaggrin. Filaggrin plays a central role in atopic dermatitis and is a key protein for the epidermal barrier. It aggregates keratins and is cross-linked to cornified envelopes. Following its deimination, it is totally degraded to release free amino acids, contributing to the natural moisturizing factor (NMF). The mechanisms controlling this multistep catabolism in human are unknown. ObjectiveTo test whether external humidity plays a role, and investigate the molecular mechanisms involved. MethodsSpecimens of reconstructed human epidermis (RHEs) produced in humid or dry conditions (>95% or 30–50% relative humidity) were compared. ResultsRHEs produced in the dry condition presented structural changes, including a thicker stratum corneum and a larger amount of keratohyalin granules. The transepidermal water loss and the stratum corneum pH were decreased whereas the quantity of NMF was greater. This highly suggested that filaggrin proteolysis was up-regulated. The expression/activity of the proteases involved in filaggrin breakdown did not increase while PAD1 expression and the deimination rate of proteins, including filaggrin, were drastically enhanced. Partial inhibition of PADs with Cl-amidine reversed the effect of dryness on filaggrin breakdown. ConclusionThese results demonstrate the importance of external humidity in the control of human filaggrin metabolism, and suggest that deimination plays a major role in this regulation.

Sensitive Skin: Assessment of the Skin Barrier Using Confocal Raman Microspectroscopy

Background/Aims: Sensitive skin (SS), a frequently reported condition in the Western world, has been suggested to be underlined by an impaired skin barrier. The aim of this study was to investigate the skin barrier molecular composition in SS subjects using confocal Raman microspectroscopy (CRS), and to compare it with that of non-SS (NSS) individuals as well as atopic dermatitis (AD) and allergic rhinoconjunctivitis (AR) subjects, who frequently report SS. Methods: Subjects with SS (n = 29), NSS (n = 30), AD (n = 11), and AR (n = 27) were included. Stratum corneum (SC) thickness, water, ceramides/fatty acids, and natural moisturizing factor (NMF) were measured by CRS along with transepidermal water loss and capacitance on the ventral forearm, thenar, and cheek. Sebum levels were additionally measured on the forearm and cheek. Results: No differences between SS and NSS subjects were found regarding SC thickness, water, and NMF content, yet a trend towards lower ceramides/fatty acids was observed in the cheek. Compared to AD subjects, the SS group showed higher ceramides/fatty acid content in the forearm, whereas no differences emerged with AR. The correlation of macroscopic biophysical techniques and CRS was weak, yet CRS confirmed the well-known lower content of NMF and water, and thinner SC in subjects with filaggrin mutations. Conclusion: The skin barrier in SS is not impaired in terms of SC thickness, water, NMF, and ceramides/fatty acid content. The failure of biophysical techniques to follow alterations in the molecular composition of the skin barrier revealed by CRS emphasizes a strong need in sensitive and specific tools for in vivo skin barrier analysis.

Determination of natural moisturizing factors in the skin: Raman microspectroscopy versus HPLC

Background: Natural moisturizing factor (NMF) is used as genotypic and phenotypic biomarker in diagnostics. This study is a side-to-side comparison of two different methods to determine NMF in atopic dermatitis patients: Raman microspectroscopy and stratum corneum tape stripping followed by HPLC.Results: Measured NMF values were significantly correlated (R2 = .61; p < .0001), both methods demonstrated a concentration-depth dependence of NMF and reduced NMF levels in the carriers of filaggrin null mutations. Good agreement between measurements of left and right arms indicated robustness and good reproducibility of both methods.Conclusions: Both methods showed comparable performance, choice of method will rather be influenced by practical consideration.

Direct quantitative analysis of the natural moisturizing factor (NMF) in the stratum corneum by direct analysis in real time mass spectrometry (DART-MS)

Analyzing the natural moisturizing factor (NMF) in the stratum corneum (SC), such as amino acids, pyrrolidone carboxylic acid, and urocanic acid, is important in dermatology research.

Adiponectin Upregulates Filaggrin Expression via SIRT1-Mediated Signaling in Human Normal Keratinocytes.

BackgroundFilaggrin (FLG) is the major component of the epidermal granular layer and binds to and condenses the keratin cytoskeleton. FLG thus contributes to cell compaction and serves as a natural moisturizing factor by promoting unfolding and degradation into hygroscopic amino acids. Loss or downregulation of FLG has been shown to result in a weak stratum corneum, which causes water loss and increases the possibility of skin barrier-related seizure. Adiponectin (Acrp30) contributes to the functional recovery of somatic cells, including human normal epidermal keratinocytes (NHEKs).ObjectiveTo investigate the effect of Acrp30 in FLG expression and identifying its signal transduction mechanism.MethodsNormal human keratinocytes were treated with Acrp30 and the levels of FLG were examined. Silent mating type information regulation 2 homolog (SIRT)-targeting siRNA and aryl hydrocarbon receptor nuclear translocator (ARNT)-targeting siRNA were used to identify the role of various signal transduction pathway components.ResultsAcrp30 upregulated SIRT1 and ARNT expression in NHEKs, resulting in increased FLG expression. Treatment with both SIRT1-targeting siRNA and ARNT-targeting siRNA blocked Acrp30 stimulation and silenced FLG expression.ConclusionAdiponectin upregulates FLG expression through a SIRT1-mediated pathway. Our results suggest that Acrp30 is a promising agent for skin barrier permeability improvement.

Expression of Filaggrin and its Degradation Products in Human Skin Following Erythemal Doses of Ultraviolet B Irradiation.

Epidermal filaggrin level is affected by ultraviolet B irradiation in animal and experimental models. This study examined the effect of ultraviolet B irradiation on epidermal filaggrin and natural moisturizing factors in vivo in healthy adults (n = 22). Participants were irradiated with 2 minimal erythema doses of ultraviolet B on the skin. Biopsies and tape strips were collected from skin irradiated 24 and 72 h earlier and from non-irradiated skin (control). Real-time quantitative PCR on skin biopsies showed significantly reduced profilaggrin mRNA expression 24 h after irradiation (mean relative mRNA expression ± standard deviation: control, 3.86 ± 2.06 vs. 24 h, 1.52 ± 0.640; p = 0.02; n = 8). Immunohistochemistry showed aberrant spatial distribution of filaggrin protein 72 h after irradiation (n = 3). High-pressure liquid chromatography of tape extracts showed no change in mean total natural moisturizing factor levels after irradiation, but mean trans-urocanic acid was significantly reduced, as expected (n = 8). In conclusion, erythemal doses of ultraviolet B exert acute effects on profilaggrin mRNA and filaggrin protein in human skin in vivo.

Sweat Facilitated Amino Acid Losses in Male Athletes during Exercise at 32-34°C.

Sweat contains amino acids and electrolytes derived from plasma and athletes can lose 1-2L of sweat per hour during exercise. Sweat may also contain contributions of amino acids as well as urea, sodium and potassium from the natural moisturizing factors (NMF) produced in the stratum corneum. In preliminary experiments, one participant was tested on three separate occasions to compare sweat composition with surface water washings from the same area of skin to assess contributions from NMF. Two participants performed a 40 minute self-paced cycle session with sweat collected from cleansed skin at regular intervals to assess the contributions to the sweat load from NMF over the period of exercise. The main study investigated sweat amino acid composition collected from nineteen male athletes following standardised endurance exercise regimes at 32–34°C and 20–30% RH. Plasma was also collected from ten of the athletes to compare sweat and plasma composition of amino acids. The amino acid profiles of the skin washings were similar to the sweat, suggesting that the NMF could contribute certain amino acids into sweat. Since the sweat collected from athletes contained some amino acid contributions from the skin, this fluid was subsequently referred to as “faux” sweat. Samples taken over 40 minutes of exercise showed that these contributions diminished over time and were minimal at 35 minutes. In the main study, the faux sweat samples collected from the athletes with minimal NMF contributions, were characterised by relatively high levels of serine, histidine, ornithine, glycine and alanine compared with the corresponding levels measured in the plasma. Aspartic acid was detected in faux sweat but not in the plasma. Glutamine and proline were lower in the faux sweat than plasma in all the athletes. Three phenotypic groups of athletes were defined based on faux sweat volumes and composition profiles of amino acids with varying relative abundances of histidine, serine, glycine and ornithine. It was concluded that for some individuals, faux sweat resulting from exercise at 32–34°C and 20–30% RH posed a potentially significant source of amino acid loss.

Development of stratum corneum chymotrypsin-like protease activity and natural moisturizing factors from birth to 4 weeks of age compared with adults.

From birth, the functional properties of the neonatal epidermal barrier mature whereby the stratum corneum (SC) hydrates and the skin surface acidifies. The identification of a thinner infant SC compared with adults suggests underdeveloped mechanisms underlying differentiation and desquamation. To assess the functional properties of the neonatal SC from birth, in conjunction with the quantification of superficial chymotrypsin-like protease activity [kallikrein-7 (KLK-7)] and filaggrin-derived natural moisturizing factors (NMF). A total of 115 neonates recruited to the Oil in Baby SkincaRE (OBSeRvE) randomized controlled trial underwent a full evaluation of the SC at birth (< 72 h old) and at 4 weeks of age (n = 39, no oil control group) using minimally invasive instrumentation and methodology. A cohort of 20 unrelated adults was recruited for comparison. At birth NMF levels correlated with SC hydration (r = 0·50) and skin-surface pH (r = -0·54). From birth to 4 weeks, transepidermal water loss (TEWL), superficial KLK-7 activity and filaggrin-derived NMF significantly elevated. Impaired epidermal barrier function at birth (> 75th percentile TEWL) was accompanied by significantly elevated chymotrypsin-like protease activity and reduced levels of NMF. The biophysical, biological and functional properties of the developing neonatal SC are transitional from birth to 4 weeks of age and differ significantly from adults. The presence of impaired barrier function with elevated protease activity and reduced NMF at birth suggests why certain infants are predisposed to epidermal barrier breakdown and the development of atopic dermatitis.

Toluene downregulates filaggrin expression via the extracellular signal-regulated kinase and signal transducer and activator of transcription–dependent pathways

Toluene downregulates filaggrin expression via the extracellular signal-regulated kinase and signal transducer and activator of transcription–dependent pathways

Design, synthesis and characterization of linear unnatural amino acids for skin moisturization.

ObjectivesThis work aimed to design, synthesize and characterize replacement natural moisturizing factor (NMF) composed of modified hygroscopic linear amino acids to pre‐empt or repair skin barrier dysfunction.MethodsFollowing synthesis and characterization, thermo‐gravimetric analysis and quantum mechanics molecular modelling quantified and depicted water binding to the new compounds. Deliquescence relative humidity demonstrated the water‐scavenging ability of the compounds, whereas snake skin moisturizing studies showed they increased water uptake into snake skin.ResultsFrom thermal analysis, N‐hydroxyglycine showed greatest water‐holding capacity followed by N‐hydroxyserine, l‐homoserine and α‐hydroxyglycine; coupled with quantum mechanics molecular modelling, between 8 and 12 molecules of water could associate with each molecule of either N‐hydroxyglycine, N‐hydroxyserine or l‐homoserine. All of our modified amino acids were efficacious and induced similar or greater water uptake compared with the established moisturizing compounds hyaluronic acid, glycerine and urea in snake skin. Incorporated at 10% in Oilatum, N‐hydroxyserine induced >200% greater moisture uptake into dry snake skin compared to treatment with water alone, with efficacy related to the molecule structure and ability to bind to 12 water molecules. Oilatum cream spiked with all our unnatural amino acid hydrotropes increased water uptake into snake skin compared with Oilatum alone.The compound series was designed to elucidate some structure – efficacy relationships. Amino acid chirality did not affect the water‐holding capacity but did affect uptake into skin. Compounds with high melting points and bond energies tended to decrease water‐holding capacity. With isosteric replacement, the more electronegative atoms gave greater water‐holding capacities.ConclusionsThis work demonstrates the potential of unnatural amino acid hydrotropes as skin moisturizers and has developed some predictive ‘rules’ for further design and refinement of chemical structures.

A synthetic C16 omega-hydroxyphytoceramide improves skin barrier functions from diversely perturbed epidermal conditions.

Omega-hydroxyceramides (ω-OH-Cer) play a crucial role in maintaining the integrity of skin barrier. ω-OH-Cer are the primary lipid constituents of the corneocyte lipid envelope (CLE) covalently attached to the outer surface of the cornified envelope linked to involucrin to become bound form lipids in stratum corneum (SC). CLE becomes a hydrophobic impermeable layer of matured corneocyte preventing loss of natural moisturizing factor inside the corneocytes. More importantly, CLE may also play an important role in the formation of proper orientation of intercellular lipid lamellar structure by interdigitating with the intercellular lipids in a comb-like fashion. Abnormal barrier conditions associated with atopic dermatitis but also UVB-irradiated skins are known to have lowered level of bound lipids, especially ω-OH-Cer, which indicate that ω-OH-Cer play an important role in maintaining the integrity of skin barrier. In this study, protective effects of a novel synthetic C16 omega-hydroxyphytoceramides (ω-OH-phytoceramide) on skin barrier function were investigated. Epidermal barrier disruption was induced by UVB irradiation, tape-stripping in hairless mouse and human skin. Protective effect of damaged epidermis was evaluated using the measurement of transepidermal water loss and cohesion of SC. Increased keratinocyte differentiation was verified using cultured keratinocyte through western blot. Results clearly demonstrated that a synthetic C16 ω-OH-phytoceramide enhanced the integrity of SC and accelerated the recovery of damaged skin barrier function by stimulating differentiation process. In a conclusion, a synthetic C16 ω-OH-phytoceramide treatment improved epidermal homeostasis in several disrupted conditions.

The Effect of an Emollient Containing Urea, Ceramide NP, and Lactate on Skin Barrier Structure and Function in Older People with Dry Skin

Xerosis affects up to 75% of older people and develops as a result of a skin barrier defect. Emollients are widely used to treat xerosis; however, there is limited understanding of the differences between them and their effects on the skin barrier in older people. This study aimed to compare the effect of a commercially available emollient containing 5% urea, ceramide NP and lactate (test emollient) to an alternative emollient without these additives (control emollient) on the properties of the skin barrier in older people. Two cohorts of 21 volunteers aged >60 years with dry skin were recruited. The first applied the test emollient to one forearm and no treatment to the other for 28 days. The second compared the test emollient to the control emollient observing the same parameters. Effects on the skin barrier were determined by measuring skin barrier function, hydration, skin surface pH and by analysing Fourier transform infrared spectra before and after treatment. A third cohort of 6 young adults was recruited to investigate the effect of a single treatment with the test emollient on the molecular structure of the skin barrier at greater depths by employing the tape-stripping technique. The test emollient hydrated the skin to a significantly greater extent and for a longer period of time compared to the control emollient, an effect associated with a significant elevation of carboxylate groups (a marker of natural moisturizing factor content) within the stratum corneum. Furthermore, the test emollient imparted additional benefits to the structure and function of the skin barrier not exhibited by the control emollient. In conclusion, the test emollient addressed the pathological features of xerotic aged skin, supporting its use as first-line therapy for xerotic skin conditions in this population.

Variation in the activities of late stage filaggrin processing enzymes, calpain-1 and bleomycin hydrolase, together with pyrrolidone carboxylic acid levels, corneocyte phenotypes and plasmin activities in non-sun-exposed and sun-exposed facial stratum corneum of different ethnicities.

Knowledge of the ethnic differences and effects of photodamage on the relative amounts of natural moisturizing factor (NMF) together with filaggrin processing enzymes in facial stratum corneum is limited. Our aim was to characterize the activities of calpain-1 (C-1), bleomycin hydrolase (BH) and the levels of pyrrolidone carboxylic acid (PCA) as a marker for total NMF levels and to relate them to plasmin activities and corneocyte maturation. Enzyme activities, PCA levels and corneocyte maturation were determined from facial tape strippings of photoexposed cheek and photoprotected post-auricular areas (PA) of healthy Caucasian (C), Black African (BA) and albino African (AA) female subjects living in South Africa. PCA concentration levels were of the order AA > BA > C subjects, and the highest activities of BH were present in the AA subjects. BH activities were greater on the photoexposed sites for the BA and C subjects, but they were only numerically elevated in the AA subjects. Photoprotected sites had an increase in C-1 activity in pigmented groups (C and BA), whereas in the AA subjects, the opposite was measured. Plasmin activities were greater on the cheek compared with the PA site for the AA and C subjects, but the activity was low in the BA subjects. In both test sites, the AA, but not the BA and C subjects, had smaller, parakeratotic and less mature corneocytes. Variation in PCA levels has been found for different ethnic groups in this study (AA > BA > C subjects). The values in the AA subjects are surprising as one might expect that the lack of pigmentation, and thereby increased photodamage, might lead to lower levels. Increased BH, but not C-1 activity, was observed in the AA subjects indicating that BH is associated with PCA production to a greater extent. Surprisingly, corneocyte maturation is still impaired with elevated PCA levels in AA subjects. The higher levels of plasmin and BH activities on the cheeks, especially for AA and C subjects, suggest that they can be used as markers for epidermal photodamage.