Biophysical parameters of skin: map of human face, regional, and age-related differences

The face showed anatomical variation on reaction to chemicals, which could be related to differences in biophysical specificities of the skin. The aim of this study was to establish a map of the face for 6 biophysical parameters.10 young human volunteers (24-34 years) and 10 old volunteers (66-83 years) were studied to prepare a map of the human face based on regional variations and age-related differences by measuring various biophysical parameters. 7 locations on the face, neck, and forearm were investigated. Skin blood flow, transepidermal water loss (TEWL), stratum corneum hydration (capacitance), temperature, pH, and sebum content of the skin surface were measured. In both groups, skin blood flow in the nose showed the highest value. Perioral and nasolabial areas showed the highest TEWL values. The neck showed the highest capacitance value. The highest skin temperature was detected in the neck in the young group and in the nasolabial area in the old group. The chin showed the most alkaline pH in both groups. Nasolabial area showed the highest sebum content in the young group, as did the chin in the old group. These baseline values provide a framework to build on for ascertaining disease and intervention-related effects.     

我国正常人皮肤表面皮脂和水分含量的研究

目的：了解我国不同年龄、不同性别正常人皮肤角质层含水量、皮肤表面皮脂含量及皮肤皮脂的分泌速度。方法：利用皮肤表面皮脂测量仪和皮肤水分含量测量仪对我国北方325名正常人的前额及前臂屈侧皮肤皮脂量和皮肤含水量进行测量。结果：12岁以前,男女前额皮脂量无差异;13岁以后,男性前额的皮脂量明显高于女性。除36～50岁年龄组外,女性前额的皮脂分泌快于男性。男女前臂的皮脂量无差异。除男性13～35岁组的前额皮肤含水量高于女性外,其他各年龄组各部位男、女皮肤含水量无显著差别。13～35岁组男、女性前额的含水量均高于前臂。其他各年龄组前额和前臂皮肤含水量无明显部位差异。13-35岁组男性前额皮肤含水量最高。结论：正常人皮肤表面含水量和皮脂含量因性别、年龄和部位的不同而有差异。     

Skin barrier function in healthy volunteers as assessed by transepidermal water loss and vascular response to hexyl nicotinate: intra- and inter-individual variability

This study assesses the variability of two non-invasive methods of measuring stratum corneum barrier function in vivo . Transepidermal water loss (TEWL), and the vascular response to hexyl nicotinate (HN) penetration as determined by laser-Doppler flowmetry, were measured in a group of 21 healthy volunteers. Each time profile of the vascular response to HN penetration was analysed using the following parameters: the baseline cutaneous blood flow, the lag-time between application and initial response (to), the time between application and maximum response (t_max.), the maximum response, and the slope of the curve. TEWL measured on the left volar forearm showed a normal range of 3.9–7.6 g/m²h and a small inter-individual variability [coefficient of variation (CV) 19–4%]. TEWL values at three other forearm sites did not show differences of clinical importance compared with the left volar forearm. The parameters of the vascular response to HN penetration spanned a wider normal range than the TEWL values (CV between 33 and 52%). Repeat measurements after a 1–2 month interval showed highly reproducible individual TEWL values. The mean difference between first and second measurements was only 0.03 g/m²h: the relative difference 0.6%. The intra-individual reproducibility of t_o and t_max for HN penetration was also high (relative differences of 2.8 and 3.1%, respectively). The other vascular response parameters were less reproducible (relative differences of 6.9–18.6%). We conclude that TEWL and selected parameters of HN penetration, as non-invasive tests of the stratum corneum barrier function, yield reproducible results and are hence useful for investigations assessing the skin barrier function in various disorders.     

Frictional properties of human skin: relation to age, sex and anatomical region, stratum corneum hydration and transepidermal water loss

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.     

Barrier function parameters in various keratinization disorders: transepidermal water loss and vascular response to hexyl nicotinate

In this study, we characterized the stratum corneum barrier function in 39 patients with various keratinization disorders (autosomal dominant ichthyosis vulgaris [ADI] [n=7]. X-linked recessive ichthyosis [XRI] [n=6], autosomal recessive congenital ichthyosis [C1] [N=10]. dyskeratosis follicularis [Darier's disease: DD] [n=8], erythrokeratoderma variabilis [EKV] [n=8]). and 21 healthy volunteers, using two non-invasive methods: transepidermal water loss (TEWL) measuring outward transport of water through the skin by evaporimetry. and the vascular response to hexyl nicotinate (HN) penetration into the skin as determined by laser-Doppler flowmetry. Significantly increased TEWL values were found on the volar forearm in all three forms of ichthyosis, compared with the healthy control group, with the highest TEWL values in the CI group. The penetration of HN on the volar forearm was accelerated in patients with ADI. XRI and CI, as indicated by a shorter lag time (to) between HN application and initial vascular response. However, differentiation between CI and the other ichthyoses was not possible by this method. When using both methods in DD and EKV. no differences compared with the healthy controls could be detected on the volar forearm, where the skin was principally unaffected: only the measurements from the affected skin on alternative sites demonstrated significantly increased TEWL values. In ADI and CI. however, normal-appearing skin also showed impaired values. We conclude that both TEWL and the vascular response to penetration of HN are suitable methods to monitor the skin barrier function in keratinization disorders, and are helpful in discriminating between these disorders.     

Image analysis of the distribution of turnover rate in the stratum corneum

Background/aims: A common method to evaluate turnover rate in the stratum corneum is to measure the change in fluorescence intensity with time after dyeing the stratum corneum with fluorescent pigments. If these changes in fluorescence over time are carefully observed, the rate of decline in fluorescence intensity differs among different small areas on the skin surface. A possible relationship between these differences and dry skin has been reported. The purpose of this research was to develop a method for analyzing turnover rate in the stratum corneum in each small area on the surface of the skin as well as to investigate the variations in the inconsistencies of turnover rate. Methods: The stratum corneum at six body regions (forehead, cheek, forearm, opisthenar, back and lower leg) was dyed with dansyl chloride (DC), and the change in fluorescence intensity over time was imaged with a highly sensitive television camera through special filters. Then, the fluorescent distribution in the images was analyzed to measure the change in fluorescence intensity with time among the small areas. Also, the decline in fluorescence intensity observed was categorized using specific characteristics into six different types. Results: By attaching a filter to an ultraviolet (UV) light source in order to transmit light at the excitation wavelength and a filter to the camera lens to transmit light at the wavelength of DC fluorescence, we could image the low intensity fluorescent light from the DC without interference from the UV light exciting the DC. The characteristics of the variation in the decline in fluorescence intensity were categorized into six patterns. Type I: pattern showing a uniform decline in fluorescence intensity. Type II: pattern showing sporadic areas where fluorescence intensity declines quickly. Type III: pattern showing relatively large areas where fluorescence intensity declines slowly. Type IV: pattern showing sporadic areas of fluorescence intensity, matched with locations of keratotic plugs. Type V: pattern showing sporadic fluorescent areas, not matched with locations of keratotic plugs. Type VI: pattern showing a partial, drastic decline in fluorescence intensity occurring on inflamed skin after sunburn. Conclusions: By analyzing the image generated from a highly sensitive television camera equipped with special filters, we could measure turnover rate of the stratum corneum at any small area. The variations in Types IV and V were believed to be derived from keratotic plugs and closed comedo. Except for Type VI, observed on significant skin inflammation, Type II and Type III were believed to be the patterns that reflected variations in turnover rate in stratum corneum itself.     

Functions of the stratum corneum in systemic sclerosis as distinct from hypertrophic scar and keloid functions

Both transepidermal water loss (TEWL) and skin surface high-frequency conductance are functions of the skin barrier. Systemic sclerosis (SSc) and hypertrophic scar (HS)/keloid are characterized by abnormal fibrotic changes in the dermis. Since the close interrelationship between the epidermis and the dermis has been well established, we analyzed the stratum corneum functions of forearm skin in 39 SSc patients after assessing the degree of the skin thickening and compared those functions with 10 age-matched normal controls. We also analyzed the stratum corneum functions of HS or keloid lesions in seven patients using the same methods, and compared those functions to adjacent or contralateral normal skin in identical patients. Neither the TEWL, nor high-frequency conductance of forearm skin in SSc patients were significantly different from those in normal controls. There was no correlation between the levels of TEWL or high-frequency conductance and the degree of skin thickening in SSc. In HS or keloid conditions, high-frequency conductance was significantly elevated (42.5+/-8.9 vs. 26.4+/-5.7, P<0.001). Although TEWL was elevated, there was no statistical significance (48.6+/-39.7 vs. 25.1+/-10.1). Our results revealed that stratum corneum functions are distinct between SSc and HS or keloid. This may reflect the various natures of dermal changes, which in turn differentiate the functions of the stratum corneum in the diseases.     

昆明地区成年女性面部皮肤屏障功能检测

目的 了解昆明地区成年女性皮肤屏障功能在年龄及部位上的差异.方法 将150名昆明地区（18 ～70）岁的女性志愿者分为3个不同年龄组,分别为：青年组（18～ 34岁）、中年组（35 ～ 49岁）及老年组（50～70岁）,每组50人.采用无创性皮肤检测仪对志愿者的左侧面颊部及额中部进行水分、油脂及TEWL的检测.结果 青年组面颊部水分（38.46±5.70）、油脂（60.70±35.78）及额中部水分（39.57±5.08）、油脂（104.56±45.40）含量最高,老年组面颊部水分（31.00±6.09）、油脂（26.87±16.71）及额中部水分（32.54±5.84）、油脂（39.67±24.44）含量最低.而面颊部TEWL（10.76±3.95）及额中部TEWL（10.13±3.76）均在青年组检测值最低.各年龄组女性额中部的油脂明显高于面颊部,差异均有统计学意义（P＜0.05）,每个年龄组面颊部水分与额中部水分比较,面颊部TEWL与额中部TEWL比较均无明显差异（P＞0.05）.结论 昆明地区成年女性面颊部及额中部水分、油脂随年龄增长而逐渐减少,而TEWL值随年龄增长逐渐增大.     

Kinetics of blood flow after topical application of benzyl nicotinate on different anatomic sites

Cutaneous characteristics, e.g., thickness of the SC and density of follicles, affect the penetration of topically applied substances. In the present study, the penetration of benzyl nicotinate, causing a vasodilation, was studied on three anatomic sites (forearm, forehead and calf) differing in their skin characteristics. Therefore, the blood flow of the superficial dermal plexus and that of the larger capillaries in the deeper skin layers was simultaneously measured using a laser Doppler flowmeter. In addition, the cutaneous temperature and redness were determined as a function of time. These four biological reactions were measured in turn on a skin area treated with a gel containing benzyl nicotinate and on an untreated control area. The highest basal levels were observed on the forehead. Topical application of benzyl nicotinate resulted in an increase in each biological response. Compared to the other sites, the maximal values were reached earliest on the forehead, which also showed the fastest decrease. No significant differences were obtained comparing the kinetic data of the calf with that of the forearm. The results indicate an additional contribution by the numerous vellus hair follicles of the forehead to the penetration and exposure of the drug.     

2-kDa hyaluronan ameliorates human facial wrinkles through increased dermal collagen density related to promotion of collagen remodeling

Background/Aims

Hyaluronan (HA) oligosaccharides are involved in several biological processes, primarily collagen remodeling and wound healing. Collagen remodeling is retarded in aging skin and causes wrinkles. The aim of this study was to evaluate the effect of 2-kDa HA oligosaccharides (HA2k) on wrinkles by permeation through the stratum corneum and promotion of collagen remodeling.

Methods

A 3D skin model and excised human skin were used to evaluate the permeation of fluorescein-labeled HA2k. The effect of HA2k on collagen metabolism was evaluated by measuring the protein level of type 1 pro-collagen (COL1A1) and matrix metalloproteinase-1 (MMP-1) in the 3D skin model. 0.1% HA2k solution and vehicle control was applied to the human forearm for 8 weeks to evaluate dermal collagen density. To evaluate the effect of HA2k on depth of facial wrinkles, a randomized controlled trial was conducted with 0.1% HA2k lotion and vehicle lotion for 8 weeks.

Results

HA2k was confirmed to permeate through the stratum corneum by fluorescent microscopy. Both COL1A1 and MMP-1 were upregulated by HA2k application in a 3D skin model culture. The collagen density was higher for the HA2k-treated forearm than for the vehicle control-treated forearm after 4 weeks. The maximum wrinkle depths in the nasolabial fold and crow's feet area were significantly shallower in the HA2k lotion group than in the control group.

Conclusion

HA2k permeated the stratum corneum, activated collagen synthesis and degradation simultaneously, and ameliorated wrinkles.     

Physiological analysis of the facial skin by corneocyte morphology and stratum corneum turnover

In order to clarify the properties of facial skin, we measured corneocyte size and stratum corneum turnover rate on the face of healthy female volunteers in relation to age and compared the data with those from the flexor surface of the forearm. The corneocyte size on the face was found to be significantly smaller and the percentage of nucleated corneocytes was distinctly higher than those on the forearm. Stratum corneum turnover rate on the face was also approximately two times faster than on the forearm. The corneocyte size increased with aging on the forearm, but not on the face. Additionally, turnover rate decreased with aging on the forearm, but not on the face. These findings suggest that the facial skin is apparently influenced by some exogenous or endogenous factors which seem to overcome the influence of intrinsic aging effects.     

Functional analyses of the superficial stratum corneum in atopic xerosis

Dermatologists universally recognize that the unaffected skin of patients with atopic dermatitis tends to be dry and slightly scaly. To characterize the functional properties of the superficial stratum corneum in atopic xerosis, we studied the forearms of 28 patients with atopic dermatitis, aged 14 to 30 years, and 18 age-matched controls, with the use of mainly noninvasive methods. Patients with atopic xerosis showed markedly higher transepidermal water loss and markedly lower skin surface hydration levels than did the controls. The corneocytes in atopic xerosis tended to desquamate in clumps of cell aggregates instead of as individual cells. They contained a substantially lower amount of water-soluble amino acids, which play a role in the water-retaining capacity of stratum corneum, than did those of controls. Although the number of stratum corneum cell layers in atopic xerosis (21 +/- 4) was substantially larger than that in controls (15 +/- 1), its turnover time (7 +/- 2 days) was appreciably shorter than that for controls (14 +/- 2 days). Like those noted in the skin with increased epidermal proliferation, the size of superficial corneocytes in patients with atopic xerosis was substantially smaller than in controls. Histopathologic examination revealed acanthotic epidermis, mild perivascular mononuclear cell infiltrate, and pigment incontinence. Atopic xerosis, the dry skin of patients with atopic dermatitis, shows various stratum corneum functional impairments, probably reflecting increased epidermal proliferation due to a low-level ongoing dermatitis.     

Decreased level of ceramides in stratum corneum of atopic dermatitis: an etiologic factor in atopic dry skin?

Stratum corneum lipids are an important determinant for both water-retention function and permeability-barrier function in the stratum corneum. However, their major constituent, ceramides, have not been analyzed in detail in skin diseases such as atopic dermatitis that show defective water-retention and permeability-barrier function. In an attempt to assess the quantity of ceramides per unit mass of the stratum corneum in atopic dermatitis, stratum corneum sheet was removed from the forearm skin by stripping with cyanoacrylate resin and placed in hexane/ethanol extraction to yield stratum corneum lipids. The stratum corneum was dispersed by solubilization of cyanoacrylate resin with dimethylformamide, and after membrane filtration, the weight of the stratum corneum mass was measured. The ceramides were quantified by thin-layer chromatography and evaluated as microgram/mg stratum corneum. In the forearm skin of healthy individuals (n = 65), the total ceramide content significantly declined with increasing age. In atopic dermatitis (n = 32-35), there was a marked reduction in the amount of ceramides in the lesional forearm skin compared with those of healthy individuals of the same age. Interestingly, the non-lesional skin also exhibited a similar and significant decrease of ceramides. Among six ceramide fractions, ceramide 1 was most significantly reduced in both lesional and non-lesional skin. These findings suggest that an insufficiency of ceramides in the stratum corneum is an etiologic factor in atopic dry skin.     

Histochemical applications of skin surface biopsy

SUMMARY.— The method of skin surface biopsy in which a cyanoacrylate adhesive is used to remove a coherent strip of stratum corneum, has been used to investigate aspects of epidermal function. The Sudan dyes were employed to demonstrate sebum in the hair follicle openings. Although increased quantities of Sudanophilic material were detected with increasing time intervals before sampling, it proved impractical to measure sebum secretion quantitatively by this method. Hydrolase activity in and around hair follicle orifices of the back, forehead and forearm were demonstrated, using enzyme histochemical methods for non-specific esterase, acid phosphatase, leucine aminopeptidase and β-glucuronidase activities. Specimens from the forehead and back were found to have stronger activities than those from the forearm. Apart from the vicinity of the follicular openings, non-specific esterase activity was not normally found in the superficial stratum corneum, although scattered areas of activity were present in the deeper parts of the horny layer. Strong, non-specific esterase activity was detected in skin surface biopsies from lesions of pityriasis lichenoides and, to a lesser extent, those of psoriasis. Mitochondrial enzyme activities were retained in parakeratotic scale from patients with psoriasis, pityriasis rubra pilaris and areas made parakeratotic after repeated removal of the stratum corneum, although not from the lesions of pityriasis lichenoides. The method also proved suitable for the demonstration of melanin granules, blood pigment and sweat gland activity.     

Frictional properties of human forearm and vulvar skin: influence of age and correlation with transepidermal water loss and capacitance

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.     

Effect of regular sauna on epidermal barrier function and stratum corneum water-holding capacity in vivo in humans: a controlled study

During the last few years, sauna has become the epitome of wellness. Besides studies in general medicine evaluating the health benefit of sauna, e.g. on the cardiovascular system, no systematic study regarding skin physiology has been published. The present exploratory study was intended to analyse the effect of regular Finnish sauna on skin physiology. The effect of regular sauna bathing was assessed with non-invasive instruments: stratum corneum water-holding capacity, skin redness, transepidermal water loss and surface skin pH were analysed in 41 healthy volunteers, aged 20-49 years, in a group with regular sauna exposure compared to a control group with no regular sauna exposure. A more stable epidermal barrier function, an increase in stratum corneum hydration, a faster recovery of both elevated water loss and skin pH after exposure to 2 x 15 min sauna at 80 degrees C could be demonstrated in volunteers with regular sauna. Heart beat rate and ionic concentration in sweat as well as epidermal blood perfusion showed a training effect under regular sauna. A decrease in casual skin sebum content on the skin surface of the forehead was observed in these volunteers. The present data suggest a protective effect of regular sauna on skin physiology, especially surface pH and stratum corneum water-holding capacity.     

大连汉族414名正常人皮肤摩擦系数检测

目的 探讨大连汉族正常人皮肤摩擦系数是否与性别和年龄有关.方法 414名汉族志愿者参加本项研究,年龄2个月至79岁,男187例,女227例;平均年龄(35.80±1.33)岁.根据生长发育期将其分为3组:0～12岁为青春期前组;20～40岁为青壮年组;60～80岁为老年组.利用Courage-Khazaka多功能皮肤生理仪Frictiometer(R) FR 770 and Corneometer(R) CM 825探头分别测量不同部位皮肤摩擦系数和角质层的含水量(电容).结果 在男性,除老年组前额部位皮肤摩擦系数明显低于手背部位外(P＜0.05),在其他各年龄组中,各部位之间皮肤摩擦系数差异无统计学意义;而在女性,除青壮年组前额部位的皮肤摩擦系数明显低于手背和眼外眦部位外(P＜0.001),在其他各年龄组中,各部位之间皮肤摩擦系数差异也无统计学意义.在男性,同一部位各年龄组之间皮肤摩擦系数差异无统计学意义;然而在女性的前额部位,老年的皮肤摩擦系数明显大于青春期前和青壮年(P值均＜0.01);在女性的眼外眦和手背部位,青壮年的皮肤摩擦系数明显大于青春期前和老年(P值均＜0.01).除青壮年女性手背和眼外眦部位的皮肤摩擦系数明显大于男性外(P分别＜0.05和0.001),在其他各年龄组和各部位中,男女间皮肤摩擦系数差异无统计学意义.在青壮年男性,各部位皮肤摩擦系数与角质层的含水量呈正相关性(前额r=0.6342,P＜0.0001;眼外眦r=0.4501,P＜0.001;手背r=0.3627,P＜0.01);而在女性,仅老年前额和眼外眦的皮肤摩擦系数与角质层含水量呈正相关性(前额r=0.2797,P＜0.05;眼外眦r=0.486,P＜0.001).结论 汉族正常人皮肤摩擦系数与性别、年龄、部位及角质层含水量有关.

Abstract：

Objective To determine whether skin friction coefficient (SFC) is associated with gender and age in a normal Chinese Han population. Methods A total of 414 Chinese Han subjects including 187males and 227 females, who were aged from 0.15 to 79 years (mean age: 35.80 ± 1.33 years), were enrolled in this study. According to human development stages, subjects were divided into pre-puberty group (aged 0 - 12years), young group (aged 20 - 40 years) and old group (aged 60 - 80 years). SFC and stratum corneum capacitance were measured with A Frictiometer(R) FR 770 and Corneometer(R) CM 825 (C&K MPA 5), respectively,on the dorsal hand, forehead, as well as canthus. Results SFC was higher on the dorsal hand than on the forehead in old males (P ＜ 0.05 ), and higher on the dorsal hand and canthus than on the forehead in young females (both P ＜ 0.001 ), while no significant difference was observed between the three measured sites in other groups of females or males (all P ＞ 0.05 ). In males, SFC on each measured site was similar among the three groups. In contrast, SFC was significantly higher on the forehead of females in aged than in young and pre-puberty groups (both P ＜ 0.01 ), and on the canthus and dorsal hand of females in young than in pre-puberty and aged groups (all P ＜ 0.01 ). The SFC on the canthus and dorsal hands of young females was higher than that of age-matched males (P ＜ 0.0001 and 0.05, respectively). A positive correlation was found between SFC and stratum corneum hydration in young males (foreahead: r = 0.6342, P ＜ 0.0001; canthus: r = 0.4501, P ＜0.001; dorsal hands: r = 0.3627, P ＜ 0.01 ). Moreover, SFC on the forehead (r = 0.2797, P ＜ 0.05) and canthus (r = 0.486, P ＜ 0.001 ) was also positively correlated with stratum corneum hydration in old females.Conclusion Skin friction coefficient varies with age, gender, body sites and stratum comeum hydration in normal Han populations.     

Influence of sportive activity on skin barrier function: a quantitative evaluation of 60 athletes

While sports‐related diseases are well documented in the literature, no study regarding the physiology of athlete's skin has been published yet. However, some evidence is given for impairment of the skin barrier due to sportive activity accompanied by an increase in sweating. In this explorative study, we investigated the effect of sportive activity on skin physiology, namely stratum corneum hydration, skin surface pH, and sebum content. A total of 60 healthy Caucasian volunteers (35 females, 25 males; mean 27.35 ± 4.09) were enrolled in this study. Measurements were done before and after 45 minutes of endurance cardio training at forehead, chest, forearm, and armpits. Hydration level, sebum secretion, and pH value of hydrolipid acid film were measured with worldwide‐acknowledged biophysical measuring methods. Stratum corneum hydration significantly increased after sportive activity. The increase was about 51.9% at the forearm and 31.9% at the chest. Sebum content at the forehead significantly decreased during exercising, from 87.36 μg/cm² to 62.41 μg/cm². At all investigated body sites, measured values for skin surface pH increased after sportive activity. Highest pH value was measured in armpits (pH 5.64–5.98) and lowest at forearm (pH 4.75–4.93). Sportive activity is accompanied by significant changes of skin physiology that could stress the barrier function of the skin. Higher skin surface pH and hyperhydration of the stratum corneum as well as increased lipid content on the skin surface are probably caused by an increased sweat production. The impaired skin barrier may also be the reason for some reported sports‐related dermatoses.     

Moisturizing effects of topical nicotinamide on atopic dry skin

BACKGROUND: Certain moisturizers can improve skin barrier function in atopic dermatitis. The effect of topical nicotinamide on atopic dry skin is unknown. We examined the effect of topical nicotinamide on atopic dry skin and compared the results with the effect of white petrolatum in a left-right comparison study. METHODS: Twenty-eight patients with atopic dermatitis, with symmetrical lesions of dry skin on both forearms, were enrolled, and were instructed to apply nicotinamide cream containing 2% nicotinamide on the left forearm and white petrolatum on the right forearm, twice daily over a 4- or 8-week treatment period. Transepidermal water loss and stratum corneum hydration were measured by instrumental devices. The amount of the stratum corneum exfoliated by tape stripping (desquamation index) was determined by an image analyzer. RESULTS: Nicotinamide significantly decreased transepidermal water loss, but white petrolatum did not show any significant effect. Both nicotinamide and white petrolatum increased stratum corneum hydration, but nicotinamide was significantly more effective than white petrolatum. The desquamation index was positively correlated with stratum corneum hydration at baseline and gradually increased in the nicotinamide group, but not in the white petrolatum group. CONCLUSIONS: Nicotinamide cream is a more effective moisturizer than white petrolatum on atopic dry skin, and may be used as a treatment adjunct in atopic dermatitis.     

Depth profiling of stratum corneum biophysical and molecular properties

Background The barrier function of the skin may be characterized by a number of biophysical and molecular methods. Variation in the barrier properties as a function of depth has not been explored in detail. Objectives To characterize changes in corneocyte surface area, corneocyte maturity, selected protease activities and transepidermal water loss (TEWL) in the ventral forearm with increasing depth. Methods The left mid‐ventral forearm of 22 healthy volunteers was selected as the study site. After tape stripping, corneocyte maturity and surface area were assessed. The protease activity of the desquamatory kallikrein proteases, KLK5 and KLK7, and inflammatory tryptase was measured using a fluorogenic probe assay. Protein content and TEWL were also recorded. Results Corneocyte maturity and surface area decreased with increasing number of tape strippings, i.e. depth into the skin. More mature corneocytes were typically larger than less mature corneocytes. The protease activities of both the desquamatory and inflammatory enzymes together with the protein content were highest in the outer layers of the stratum corneum and decreased with depth. As expected, TEWL increased as more stratum corneum layers were removed. There were no statistical differences between men and women or caucasian and black subjects for all of the parameters studied. Conclusions The techniques used in this study provide rapid noninvasive measures of the spatial distribution of corneocyte maturity and surface area as well as protease activity and protein content within different levels of the stratum corneum layers. The methods used will allow mechanistic insight into the effects of formulation excipients and active ingredients on epidermal turnover and skin barrier function.