Using a recently developed noninvasive, in vivo suction device for measuring skin elasticity, we evaluated age, sex, and regional differences in the viscoelastic properties of skin. A total of 33 volunteers participated in the study consisting of (a) 8 young females, (b) 9 old females, (c) 8 young males and (d) 8 old males. Measurements were performed on 11 anatomical regions; three different loads were applied: 100, 200, and 500 mbar. The parameters used were: immediate distension (Ue); delayed distension (Uv); immediate retraction (Ur); and, final deformation (Uf). To compare between subjects and anatomical regions, relative parameters independent of skin thickness were calculated: Uv/Ue, the ratio between the viscoelastic properties of skin and immediate distension, and Ur/Uf, which measures the ability of the skin to regain its initial position after deformation. Generally, Uv/Ue increased while Ur/Uf decreased with aging. Responses were variable with respect to load applied. Variability within anatomical regions was also noted. However, differences between the sexes were not statistically significant for most regions. These findings are in congruence with earlier studies suggesting the differences are mainly attributable to alterations in the elastic fiber network. This procedure provides a simple, quantitative assessment of elastic properties of the skin. Its application may help in future investigations of other connective tissue disorders.

This report reviews individual-related variables (age, sex, race, anatomical site, skin surface properties), intra-and interindividual variation (temporal, physical and mental activity, orthostatic effect, menstrual cycle/menopause), environment-related variables (light conditions, temperature) and various instrument-related variables that influence skin colour. CIE colorimetry (Minolta Chroma Meter) and spectrophotometric measurement (DermaSpectrometer) are considered. The guidelines give recommendations for measuring conditions and procedures.

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Differences in the dynamic skin friction coefficients (ji) 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 /J (O 34 ± o 02) while the abdomen had the lowest (012 ± o 01); the remaining regions had an average fi value of 021 ±001. 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 ^ and capacitance for most regions. Between n 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.One basic physical function of the skin is the friction necessary for grasping, gripping, and locomotion. Awareness of the importance of the frictional properties of skin has arisen from Correspondence: Professor H.I.Maibach,

To investigate differences in response to irritation according to age and site seven young-adult and eight elderly females were exposed to 0.25% sodium lauryl sulphate (SLS) under patch-test occlusion for 24 h. Ten anatomical regions were tested: forehead, upper arm, volar and dorsal forearm, postauricular, palm, abdomen, upper back, thigh, and ankle. The skin responses were evaluated 24 h post-patch removal by visual scoring and by transepidermal water loss measurements (TEWL). Non-treated symmetrical anatomical regions served as controls. SLS induced a mild erythematous reaction on most anatomical regions except the palm and TEWL was significantly increased as compared with controls. The elderly group demonstrated significantly less susceptibility to SLS-induced irritation for most regions of the body as indicated by visual scores and TEWL measurements. In addition, evaluation of the stratum corneum water content following SLS irritation demonstrated lower responses in the old age group for most regions. The thigh had the highest reactivity and the palm the lowest, in both age groups. These data suggest that young adult skin is more sensitive to SLS than old skin and that SLS irritation varies considerably with respect to region. Moreover, objective TEWL measurements seem to be a better indicator of irritant susceptibility, especially in the elderly, than clinical evaluation by visual scoring.

The ageing process is noticeable within all organs of the body and manifests itself visibly in the skin. Skin ageing is influenced by several factors including genetics, environmental exposure, hormonal changes and metabolic processes. Together these factors lead to cumulative alterations of skin structure, function and appearance. The functioning of the central nervous, immune, endocrine and cardiovascular systems, as well as the skin is also impaired with age. Chronologically, aged skin is thin, relatively flattened, dry and unblemished, with some loss of elasticity and age-related loss of architectural regularity. General atrophy of the extracellular matrix is reflected by a decrease in the number of fibroblasts. Reduced levels of collagen and elastin, with impaired organization are primarily because of decreased protein synthesis affecting types I and III collagen in the dermis, with an increased breakdown of extracellular matrix proteins. Oxidative stress is considered of primary importance in driving the ageing process. The original free radical theory of ageing purported that the molecular basis of ageing was derived from a lifetime accumulation of oxidative damage to cells resulting from excess reactive oxygen species (ROS) produced as a consequence of aerobic metabolism. Although the skin possesses extremely efficient anti-oxidant activities, during ageing, ROS levels rise and anti-oxidant activities decline. The ROS are necessary in multiple MAP kinase pathways and the induction of AP-1, in turn, up-regulates expression of matrix-metalloproteinases providing a plausible mechanism for the increased collagen degradation in aged human skin. Ré suméLe processus de vieillissement est perceptible sur tous les organes du corps et se manifeste clairement au niveau de la peau. Le vieillissement de la peau est influencée par plusieurs facteurs comme la génétique, l'exposition environnementale, les variations hormonales, les mécanismes métaboli-ques. Ensemble, ces différents facteurs conduisent à des altérations cumulatives de la structure de la peau, de sa fonction et de son apparence. Le fonctionnement du système nerveux central, immunitaire, endocrinien et cardio-vasculaire est, comme la peau, touché par l'âge. La peau âgée est fine, relativement relâchée, sèche et sans défaut avec

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Despite its heterogeneity, stratum corneum (SC) has been described as a homogeneous membrane for water diffusion. We measured water flux across the SC, transepidermal water loss (TEWL), in six women, in vivo. At four anatomical sites--back, abdomen, forearm, and thigh--we took measurements during sequential tape stripping. The inverse of TEWL (1/TEWL) and removed SC thickness yielded a highly linear correlation (Pearson's r ranging between 0.88 and 0.99). Applying Fick's law of diffusion, we calculated SC thickness (H), and SC water diffusion coefficient (D). Comparing the results, SC of all women was significantly thicker (p < 0.05) at the extremities (12.7 +/- 4.2 microm, mean +/- SD, n = 12) than the abdomen (7.7 +/- 1.8 microm, n = 6). The calculated diffusion coefficient approximated 2.16 +/- 1.14x10(-9) cm2/s. Compared with the diffusion constant found for SC depleted of lipids, our value was 100-fold lower. In agreement with previous findings that intercellular lipids are a rate determining component of the SC barrier, we suggest that water diffuses mainly through the intercellular space. The calculation of H and/or D, however, is based on several variables: SC density, the water concentration difference, and the partition coefficient of water between viable epidermis and SC. The literature values vary widely. It is desirable to determine these parameters more precisely, especially if discrete differences, such as between anatomical sites, are to be revealed.