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.     

Instrumental and clinical studies of the facial skin tone and pigmentation of Shanghaiese women. Changes induced by age and a cosmetic whitening product

The pigmentation patterns of facial skin of 354 healthy Chinese women aged 18–80 years were investigated clinically and instrumentally. Chromasphere^® was used to acquire pictures from the cheeks of subjects. Facial skin tone was described by L* parameter from the L,a,b system as well as Individual Typology Angle (ITA). Results show that skin tone becomes significantly darker along the life span. Both size of hyper‐pigmented spots and their contrast with surrounding skin were found increased with age. As additional study, 40 women from these 354 subjects were asked to apply daily a whitening cosmetic product for a 2‐month period. Such application led to a significantly lighter skin tone, although this study was not vehicle controlled and we cannot exclude that the increase in L* observed was in some part because of cumulative effects of previously used whitening products, there was an association with lighter skin tone as assessed through both instrumental measurements and self‐perception by most subjects.     

Short‐term in vivo digestibility assessment of a highly oxidized and polymerized sunflower oil

The aim of this study was to test the in vivo digestibility of a highly polymerized sunflower oil. The true digestibility of both the unheated oil and of an oil heated at frying temperature (180 °C) for 50 h in the presence of air was determined by using a 4 h in vivo test after applying the oil by an oesophageal probe to Wistar rats followed by high‐performance exclusion chromatography analysis of the luminal remaining fat. The true digestibility coefficient of the heated oil did not change significantly with respect to the unheated oil, although it tended to decrease (p < 0.1; 38%). The true digestibility of polymers, dimers, and total oligomers was 30%, 59%, and 38% respectively, whereas those of the unheated oil was much higher (95%, 90%, and 91% respectively). True digestibility did not change for the triacylglycerol monomers. The plasma concentration of triacylglycerol tended to decrease (9.7%; p > 0.05) in the rats receiving the heated oil, suggesting some delay in the absorption mechanism. Data show that thermoxidized compounds from abused oil are poorly but actively hydrolysed and absorbed in vivo. Copyright © 2003 Society of Chemical Industry     

Facial skin mapping: from single point bio‐instrumental evaluation to continuous visualization of skin hydration,barrier function,skin surface pH,and sebum in different ethnic skin types

Dry skin is one of the most important concerns of consumers worldwide. Despite huge efforts over several decades, the personal care industry still does not offer a perfect solution to satisfy the unmet needs of consumers for moisturising treatments in different ethnic groups. The paucity of data for the underlying cellular and biochemical problems in, and the effects of moisturisers on photodamaged facial skin may partly explain this. Mainly, single point measurements are used to understand the effects of products on skin physiology even on surrogate skin sites such as the non‐photodamaged volar forearm. Some groups have developed discontinuous facial maps of skin biophysical properties, however, in 2014 a continuous facial analysis of bio‐instrumental evaluations was developed using a heat map approach. These maps enabled a continuous visualization of features that not only revealed an unexpected complexity of facial skin but also indicated that use of surrogate skin sites for facial skin is inappropriate. We have demonstrated that remarkable gradients of skin hydration, TEWL, skin surface pH and sebum exist within short distances across the face and the gradients are distinctive among different ethnic groups. In addition, these studies have demonstrated that darkly‐pigmented individuals do not necessarily have a better skin barrier function than their less‐pigmented counterparts and that Caucasians have a lower facial skin surface pH compared with more pigmented subjects. Overall, there are no correlations between capacitance, TEWL and skin surface pH including individual topology angle values. Novel 3D camera approaches have also been used to facilitate a more precise assignment of measurement sites and visualisation. The 3D facial colour mappings illustrated precisely the local moisturising effects of a moisturising cream. There were subtle ethnic differences in efficacy that may be related to underlying skin biochemistry and/or ethnic differences in product application. A placebo‐controlled study using conductance measurements in Chinese subjects is also reported. Finally, a new whole face statistical approach has been taken to prove differences in skin parameters but also of moisturiser treatment that adds further to our understanding of the ethnic differences in skin physiology and product application. This paper reviews the background of the development and application of this methodology.