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

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

混合植物油与白油对皮肤的综合作用比较

通过让受试者分别在前臂内侧皮肤（6h短效试验组）和面部皮肤（30d长效试验组）上使用含混合植物油和白油的膏霜样品,考察了混合植物油和白油对皮肤水分含量、经表皮失水率（TEWL）、摩擦力、弹性的短期和长期影响以及对皮肤皱纹的长期影响。结果显示,混合植物油在短期和长期内均能有效提高皮肤水分含量和降低水分流失,长期使用能有效提高皮肤弹性和降低皮肤皱纹面积、皱纹长度、皱纹深度;白油在短期和长期内也能一定程度提高皮肤水分含量和减少水分流失,长期使用对皮肤皱纹深度有降低作用,效果均不及植物油。涂抹后6小时,植物油能降低皮肤摩擦力,白油能提高皮肤摩擦力,长期使用两种油脂均能提高皮肤摩擦力。     

化妆品保湿功效评价研究

通过测定不同质量分数保湿剂的皮肤水分含量（MMV）值和经表皮水分散失（TEWL）值,研究了保湿功效评价方法。研究得到了不同质量分数的保湿剂在化妆品配方中的保湿效果存在显著性差异,啫哩配方中的基质成分主要是水,能够准确地测定出添加保湿剂的保湿功效;而乳液配方中的基质含有保湿成分,测定保湿剂与基质复合的保湿功效。结果表明,通过测定MMV和TEWL评定化妆品保湿性具有准确度高和灵敏度好且易操作等特点,能够全面综合地评价化妆品保湿功效,是保湿化妆品功效评价的有效方法。     

Reduced barrier efficiency in axillary stratum corneum

The skin of the axilla is cosmetically important with millions of consumers daily applying antiperspirant/deodorant products. Despite this, we know virtually nothing about axillary skin or how antiperspirant (AP) use impacts upon it. To characterize the axillary stratum corneum and determine whether this is a unique skin type, we have looked at stratum corneum composition and function, particularly its barrier properties, and compared it with other body sites. Transepidermal water loss (TEWL) and corneosurfametry (CSM) revealed a reduced barrier function in the axilla. HPTLC analysis of the stratum corneum lipids demonstrated statistically elevated levels of fatty acids, ceramides, and particularly cholesterol in the axilla. Both ceramide and cholesterol did not appear to change with depth, indicating that they were predominantly of stratum corneum origin. On the other hand, at least some of the fatty acid had a sebaceous origin. We hypothesized that the reduced barrier function might be owing to the changes in the crucial ceramide : cholesterol ratio. To address this, we used a combination of attenuated total reflectance-Fourier-transformed infrared spectroscopy (ATR-FTIR) with cyanoacrylate sampling. These results demonstrated more ordered lipid-lamellae phase behaviour in the axilla, suggesting that the elevated cholesterol might form crystal microdomains within the lipid lamellae, allowing an increase in water flux. Since an exaggerated application of antiperspirant had no effect upon the axilla barrier properties, it is concluded that this region of skin physiologically has a reduced barrier function.     

丝素共混膜在化妆品保湿效果评价中的应用初探

利用皮肤水分含量测试仪和水分散失测定仪,对添加不同质量分数甘油的保湿化妆品作用前后丝素共混膜的水分含量值（MMV）和经表皮水分散失值（TEWL）进行测定,以人体试验为参比,创造性地探索丝素共混膜在化妆品保湿效果评价中的应用价值,并对保湿类化妆品中保湿剂的最佳添加量做出指导。结果发现,丝素共混膜模拟体系的试验结果和人体试验具有相似的趋势,以其作为化妆品保湿效果评价的人体替代试验具有一定的可能性。     

In vivo barrier challenge and long‐term recovery in human facial skin

Recently, we developed a biophysical approach to characterize in vivo facial cheek skin as a function of stratum corneum (SC) depth, barrier function and during a 24‐h recovery period. The current study extends this work and characterizes the human facial cheek after barrier challenge and, for the first time, facial SC barrier recovery over a 4‐week period. Changes in the corneocyte size over the 4‐week recovery period, and correlations with changes in Trans‐Epidermal Water Loss (TEWL) were monitored. This approach allows complete characterization of SC barrier function after a full biological regeneration of the SC barrier following tape stripping. The structural and compositional changes in facial cheek were investigated using Attenuated Total Reflectance‐Fourier Transform Infra Red (ATR‐FTIR) spectroscopy, tape stripping, TEWL measurements and image analysis combined with optical microscopy to characterize the SC depth profile during the tape stripping stress and over 4‐week recovery period. TEWL increased significantly from baseline after sequential tape stripping. Corneocyte size decreased with successive tape stripping. An inverse direct correlation was determined between TEWL and corneocyte surface area. After 4 weeks, the corneocyte size and TEWL for the facial cheek recovered 100% from the tape stripping procedure. The in vivo ATR‐FTIR data demonstrated that lipid and sebum components on the surface of the facial cheek SC recovered within 24 h post tape stripping, whereas protein (Amide II) and water components recovered after 1 week.     

皮肤刺激的仪器评价

在志愿者皮肤斑贴受试物或物理性损伤皮肤后,比较了TEML仪（Tewamter TM210)与其他几种仪器如Minlta色差仪,电导仪（Skicom200)和电容仪（Corneometer CM820)在检测肤损伤的敏感性。结果表明,TEWL仪在检测低皮肤刺激性上优于其他的仪器检测,TEML的增加能敏感地反映由于皮肤屏障破坏而造成的皮肤刺激作用。     

Hydration of the stratum corneum

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.