To read the full-text of this research, you can request a copy directly from the authors.
Objective: To analyze the skin barrier function in different subjective skin types. Methods: Ninety women aged 20-25 years old in Beijing city were recruited and categorized into oily, neutral and dry skin (n=30 in each group), according to their subjective skin types. Non-invasive methods were used to measure the sebum excretion rate (SER), stratum corneum hydration, skin surface pH and transepidermal water loss (TEWL). The stratum corneum integrity was determined by assessing the changes in TEWL values following each tape-stripping. The stratum corneum adhesion and serine protease activity were compared among groups. Results: Neutral skin displayed the best permeability barrier among the three types of skin. TEWL, PH and serine protease activity on the cheeks were higher in both oily and dry skin than in neutral skin. The oily skin was characterized by impaired stratum corneum integrity, while dry skin had poor stratum corneum cohesion. Conclusions: Both oily skin and dry skin exhibit certain extent of permeability barrier abnormality compared with neutral skin. The characteristic differences between oily skin and dry skin are associated with the different mechanisms of their barrier impairment.
This article deals with the tribology of lipid coatings that resemble those found on human skin. In order to simulate the
lipidic surface chemistry of human skin, an artificial sebum formulation that closely resembles human sebum was spray-coated
onto mechanical skin models in physiologically relevant concentrations (5–100μg/cm2). Water contact angles and surface free energies (SFEs) showed that model surfaces with ≤25μg/cm2 lipids appropriately mimic the physico-chemical properties of dry, sebum-poor skin regions. In friction experiments with
a steel ball, lipid-coated model surfaces demonstrated lubrication effects over a wide range of sliding velocities and normal
loads. In friction measurements on model surfaces as a function of lipid-film thickness, a clear minimum in the friction coefficient
(COF) was observed in the case of hydrophilic, high-SFE materials (steel, glass), with the lowest COF (≈0.5) against skin
model surfaces being found at 25μg/cm2 lipids. For hydrophobic, low-SFE polymers, the COF was considerably lower (0.4 for PP, 0.16 for PTFE) and relatively independent
of the lipid amount, indicating that both the mechanical and surface-chemical properties of the sliders strongly influence
the friction behaviour of the skin-model surfaces. Lipid-coated skin models might be a valuable tool not only for tribologists
but also for cosmetic chemists, in that they allow the objective study of friction, adhesion and wetting behaviour of liquids
and emulsions on simulated skin-surface conditions.
Facial skin is usually classified as dry, normal, and oily in the cosmetics field. However, there is no standard objective method for classifying facial skin.
We measured sebum excretion with Sebumeter at four sites on the face. Based on the amount of sebum secretion, we reclassified skin type according to the guidelines provided by the manufacturer. The mean of sebum excretion (mean facial sebum excretion; MFSE) was also calculated.
People secrete varying amounts of sebum at different skin sites. Reclassification of skin type based on sebum secretion revealed that most participants underestimated the amount of facial sebum excretion. When sebum secretion amounts were compared, a statistically significant difference was apparent between the oily and dry skin types. However, there were no statistical differences between oily and normal, and normal and dry skin.
We showed that subjective skin type does not match the amount of sebum secreted. Thus, this simple and subjective classification is of very limited use and it should be re-evaluated by using an objective and standardized measuring tool.
Differences of skin type and pH between subjects with and without acne have not been investigated. In addition, the relationship between sebum secretion and pH in these populations has not been determined. This study assessed the differences in objective and subjective skin types between these two groups. Secondly, this study evaluated the difference in pH on five facial areas (forehead, nose, chin, right and left cheeks) between the two populations. Lastly, the relationship between pH and sebum secretion was analyzed in each population. Sebum casual levels (CL) of the five facial areas in 36 Koreans with acne and 47 Koreans without acne were measured by using a Sebumeter SM 815® and subjects were classified into objective skin types by CL. Subjects reported the type of skin they believed they had, which determined the subjective skin type. The pH levels of the five facial areas were measured by the Skin-pH-Meter PH 905®. Data were assessed with adequate statistical tests depending on data type and distribution. Among the five areas, the nose of the subjects with acne showed a significantly higher CL, compared to the subjects without acne. This difference in CL on the nose resulted in the difference in CL on the T-zone and mean facial sebum excretions (MFSE). Although CL differed, objective skin types did not differ between the two groups (P > 0.05), but the subjective skin types differed significantly (P = 0.001). In addition, the objective skin types were significantly different than the subjective skin types in subjects with acne (P = 0.001), whereas the two skin types did not differ in subjects without acne. Subjects with acne actually overestimated their skin types and stated their skin types were “oilier” than they were. In respect to pH, none of the five areas differed significantly between the two groups. Among the five sites in subjects with acne, CL showed a significant negative correlation with pH on the left (r
2 = 0.12) and right (r
2 = 0.15) cheeks, which resulted in a significant negative correlation on the U-zone (r
2 = 0.14). In contrast, in subjects without acne, there was a significant negative correlation between CL and pH on the forehead (r
2 = 0.10) and chin (r
2 = 0.16), which led to a significant negative correlation on the T-zone (r
2 = 0.14).
Sebaceous glands are intriguing glands that are found throughout the human body except on the palms of the hands and soles of the feet. The true function of these glands has yet to be determined, but there are several theories, including antioxidant effects, antibacterial effects, and transport of pheromones. Sebaceous glands produce lipids that are involved in the pathogenesis of one of the most prevalent diseases of adolescence, acne. Although the majority of lipids produced by the sebaceous gland are also produced in other areas of the body, there are two that are characteristic of the sebaceous gland, wax esters and squalene. This review seeks to present an update on the physiology of the sebaceous glands, with particular emphasis on the production of sebaceous lipids.
This preliminary study investigated both the impact of oily skin on quality of life (QoL) and the agreement between subjective oily skin self-assessment and objective skin surface sebum measurement in young to middle-aged Chinese women in Beijing.
A 18-item Chinese version of the Oily Skin Self-Image Questionnaire (OSSIQ) was used to assess the impact of oily skin on QoL in 300 healthy female subjects (age groups: 20-25; 26-30; 31-35,). The subjects were divided equally into the oily skin group and the non-oily skin group based on their self-perception of skin oiliness. The level of skin surface lipids (SSL) was measured on the middle of the forehead, and both cheeks using the Sebumeter(®). In order to assess the agreement between self-perceived skin oiliness and measured SSL, we tentatively used the SSL median value as a dividing point to regroup all subjects.
The results indicate that the Chinese version of the OSSIQ distinguished the oily skin group from the non-oily skin group. Subjects in the oily skin group had significant higher emotional status score and behavior score when compared with subjects in the non-oily skin group. Subjects in the oily skin group had higher SSL when compared with subjects in the non-oily skin group, especially in younger age groups. The agreement between self-perceived skin oiliness and measured SSL was moderately strong in younger age groups, and declined with age.
These results strongly suggest that having oily skin can cause a significant negative impact on QoL among Chinese women. The Chinese version of the OSSIQ is a reliable and valid tool for assessing the impact of oily skin on QoL. The accuracy of oily skin self-assessment declines with age.
This paper reviews the role of stratum corneum (SC) proteases and their inhibitors in normal and xerotic skin conditions. The importance of the corneodesmosome for SC integrity is also discussed, and the effect of proteases on its disassembly. The relevance of each enzyme class is outlined, as well as their potential inhibitors. It is becoming much clearer, however, that the LEKTI family of inhibitors are critical for SC enzyme control. Delayed desquamation is the accumulation of corneocytes on the surface of the SC that leads ultimately to the cosmetic condition commonly termed as "dry skin". The reductions of serine protease activity are a consistent theme in dry skin, and non-eczematous atopic dermatitis otherwise known as atopic xerosis leading to retention hyperkeratosis. Flaky skin is normally seen on the body whereas a rough skin is observed on the face. Increased protease activity occurs in most, if not all, inflammatory dermatoses, ranging from the genetic disorders, psoriasis and eczematous atopic dermatitis to sub-clinical barrier abnormalities induced by surfactants or by environmental influences as a result of premature desquamation. In some of these conditions a thinner SC is apparent, e.g., eczematous atopic skin or on photodamaged facial skin. A better understanding of the proteolytic events and of the regulatory mechanisms involved in desquamation should enable the design of new treatments for skin disorders associated with faulty desquamation. This new knowledge will be an important basis for new developments in 'corneotherapy' and 'corneocare'.
Background/aims: Understanding structural and functional differences between facial areas is necessary for the formulation of cosmetics and dermatological preparations well tailored to the skin's biophysical characteristics. The objective of the present study was to compare biophysical parameters on malar and frontal facial areas of healthy women classified according to self-reported cosmetic skin types.
Methods: The study population comprised 253 women aged from 20 to 50 years who did not display any signs of dermatological disease. Women declared spontaneously their cosmetic skin type. Skin capacitance, sebum casual level, skin temperature, transepidermal water loss (TEWL), skin colour and relief were assessed on cheeks and forehead in a controlled environment.
Results: All biophysical parameters showed statistically significant differences between the two zones. Mean a* chromametric values and TEWL values were significantly higher on cheeks. In contrast, mean b* chromametric values and sebum casual levels showed the highest values on the forehead. Moreover, skin capacitance, temperature, roughness and L.* chromametric value showed minor, while statistically significant, differences between the two zones. With marginal exceptions, the differences between the facial zones for each biophysical parameter remained statistically significant, irrespective of self-reported skin type.
Conclusion: Biophysical parameter mean values differ between frontal and malar zones regardless of self-reported skin type. Except for the elevated sebum casual levels in “greasy” and “combined” skin, no single or combined biophysical characteristics could be linked to any of the self-reported skin types. Furthermore our data confirm that in contrast to the common belief that “dry” skin is associated with reduced sebum production, sebum levels in women declaring to have “dry” skin and those declaring to have “normal” skin were not found to be different.
Dry skin is characterized by a decreased lipid content and a delayed reconstitution of the epidermal barrier after skin irritation. These are problems of high relevance in the aged population, especially in the development of irritant contact dermatitis. Asteatotic and perineal irritant dermatitis are the most important subtypes of irritant contact dermatitis in the elderly. This contribution presents a compressed survey on these subtypes and elucidates their relation to an impaired barrier function. Typical irritants affecting aged individuals are explained and compared with irritants that seem to be more significant in younger people. Results of biophysical investigations, such as measurement of transepidermal water loss, are discussed regarding their age-dependence. Transepidermal water loss decreases with age, which was formerly interpreted as an indication of a decreased sensitivity. Today, we know that reconstitution of the epidermal barrier after irritation is delayed once it has been impaired. Reasons are decreased activities of enzymes involved in lipid synthesis and processing, a changed cytokine profile, a reduced acidification of aged skin, and alterations in the function of epidermal stem cells. Owing to these new insights, a reevaluation of the sensitivity of aged skin has to be initiated, especially with regard to occupational dermatology.
The correlation between the degrees of integrity and cohesion in healthy human Stratum corneum (SC) and the properties of the SC lipid matrix could be examined non-invasively in vivo using ATR-FTIR spectroscopy and measurements of pH, conductance, and transepidermal water loss (TEWL) taken in the course of tape-stripping. The change of TEWL following the removal of a SC layer with a predefined thickness served as a measure for the SC integrity, and the amount of protein removed by predefined number of tapes - as a measure for the SC cohesion. The extent of lipids organized in orthorhombic lattices and the pH in the inner SC emerged as the main factors that determine the degree of integrity. The amounts and molecular organization of the SC lipids did not correlate with the degree of cohesion, while the pH and the hydration of SC correlated well with the degree of cohesion in the superficial but not in the inner SC layers. This study evidenced the variability of SC integrity and cohesion existing in healthy human skin, demonstrated the importance of the lipid molecular organization for the SC integrity, and illustrated the limitations in the determination the degree of corneodesmolysis in SC based only on the protein content of tape-strips.
Sebaceous gland activity has four distinct components which are sebum production (a secretion rate function), storage (a volume function), surface output (a delivery rate function) and stratum corneum permeation (an influx rate function). The oily appearance of skin results from an excess of sebum excretion and spreading over the body surface and its interaction with the skin surface. A multi-pronged approach is often useful to assess skin greasiness with precision. The clinical evaluation of skin greasiness and its shiny appearance should be further complemented by quantifying the large pores, follicular plugs and comedones. The sebum amount present at the skin surface can be measured non-invasively using one of several methods based on solvent extraction, cigarette paper pads, photometric assessment, bentonite clay and lipid-sensitive tapes. Quantitative parameters include the sebum casual level, the sebum excretion rate, the sebum replacement time, the instant sebum delivery, the follicular excretion rate, the density in sebum-enriched reservoirs and the sustainable rate of sebum excretion. A series of environmental and biological features influence the data. Hence rigorous methodological designs are mandatory to support claims. As a rule, accuracy of the methods is adversely affected by skin temperature, degree of hydration and surface roughness. An additional confounding factor is the inherent difficulty of collecting the surface lipids without a contribution from the follicular reservoir. A better understanding of factors that alter the sebum amount at the skin surface may well assist in the development of sebosuppressive agents to help the reduction of the skin greasiness and improve acne.
Both exposure of stratum corneum to neutral pH buffers and blockade of acidification mechanisms disturb cutaneous permeability barrier homeostasis and stratum corneum integrity/cohesion, but these approaches all introduce potentially confounding variables. To study the consequences of stratum corneum neutralization, independent of hydration, we applied two chemically unrelated superbases, 1,1,3,3-tetramethylguanidine or 1,8-diazabicyclo [5,4,0] undec-7-ene, in propylene glycol:ethanol (7:3) to hairless mouse skin and assessed whether discrete pH changes alone regulate cutaneous permeability barrier function and stratum corneum integrity/cohesion, as well as the responsible mechanisms. Both 1,1,3,3-tetramethylguanidine and 1,8-diazabicyclo [5,4,0] undec-7-ene applications increased skin surface pH in parallel with abnormalities in both barrier homeostasis and stratum corneum integrity/cohesion. The latter was attributable to rapid activation (<20 min) of serine proteases, assessed by in situ zymography, followed by serine-protease-mediated degradation of corneodesmosomes. Western blotting revealed degradation of desmoglein 1, a key corneodesmosome structural protein, in parallel with loss of corneodesmosomes. Coapplication of serine protease inhibitors with the superbase normalized stratum corneum integrity/cohesion. The superbases also delayed permeability barrier recovery, attributable to decreased beta-glucocerebrosidase activity, assessed zymographically, resulting in a lipid-processing defect on electron microscopy. These studies demonstrate unequivocally that stratum corneum neutralization alone provokes stratum corneum functional abnormalities, including aberrant permeability barrier homeostasis and decreased stratum corneum integrity/cohesion, as well as the mechanisms responsible for these abnormalities.