Comprehensive mapping of human body skin hydration: A pilot study

Age-related variations in stratum corneum hydration in the foot

OBJECTIVE

The aims of the study are to identify which region of the foot has lower hydration according to age, measure the variation in the level of stratum corneum hydration of the foot across the a wide age range, and examine hydration differences of the foot according to gender.

STUDY DESIGN

A descriptive observational study was conducted to assess stratum corneum hydration of the foot among 504 participants recruited between November 2023 and March 2024.

MAIN OUTCOMES MEASURES

Stratum corneum hydration assessment was conducted using a Corneometer 825® probe at 10 specific points on the foot. Data on sociodemographic variables, medical history, foot care habits, and hydration-related factors were collected. Statistical analyses were performed using SPSS v. 24.0.

RESULTS

Stratum corneum hydration of the foot varied significantly across regions, with higher hydration in the digital zone and lower hydration in the heel. An inverse correlation was found between age and hydration, with younger participants exhibiting higher hydration levels. Women showed higher hydration than men. Differences in hydration were observed between the right and left feet.

CONCLUSION

This study highlights the importance of localized assessment of foot skin dehydration. Aging significantly affects stratum corneum hydration of the foot. Gender differences in hydration suggest the importance of personalized approaches to skin care. Differential hydration between feet underscores the influence of mechanical load.

A comprehensive comparison of facial skin hydration based on capacitance and conductance measurements in Chinese women

OBJECTIVES

The aim of this study was to compare the data of conductance and capacitance measurements of facial skin hydration and to evaluate and discuss the advantages and disadvantages of the different approaches.

METHODS

We measured skin capacitance (Corneometer® CM 825) and skin conductance (Skicon-200EX®) on 30 pre-defined facial sites of 125 Chinese women, resulting in 3750 readings per device. The data were analysed and compared, and continuous colour maps were generated on a 3D avatar for capacitance, conductance, relative difference (Δ%) and correlation (R-value) by interpolating between the individual readings and converting the values to colours. This visualization allows a better interpretation of the results.

RESULTS

The complexity of facial skin hydration is revealed by this approach. The similarities and discrepancies in the facial hydration maps are clearly apparent. Due to the superiority of the Skicon in measuring high hydration levels, differences in skin hydration were evident on the forehead compared with the Corneometer maps, which may be related to the more superficial measurement of the Skicon within the stratum corneum. Conversely, a greater understanding of the complexity of facial skin hydration in the nasolabial fold was obvious when using the Corneometer. The best congruence between the instruments was found at two specific but separated facial areas, one around the inner eye region and the other one on a line between the nasolabial sulcus and the oblique, lateral jaw. Interestingly, the data were not normally distributed for both instruments and they had opposite skews. All facial clusters were statistically different from each other (p < 0.001), except the cheek and jaw for the Skicon. Larger than expected percentage coefficients of variance were found for the Corneometer on some facial sites that might be explainable by differences in stratum corneum physiology and biochemistry. Corneometer values of 48 AU and Skicon values of 132 μS were taken as the cutoff for normally hydrated facial skin.

CONCLUSIONS

Both devices have their advantages and disadvantages suggesting that bio-instrumental measurement of skin hydration is actually more complicated than commonly thought and that the different facial zones and the use of multiple instrumentation have not been adequately considered.

In Vivo Assessment of Water Content, Trans-Epidermial Water Loss and Thickness in Human Facial Skin

Mapping facial skin in terms of its biophysical properties plays a fundamental role in many practical applications, including, among others, forensics, medical and beauty treatments, and cosmetic and restorative surgery. In this paper we present an in vivo evaluation of the water content, trans-epidermial water loss and skin thickness in six areas of the human face: cheeks, chin, forehead, lips, neck and nose. The experiments were performed on a population of healthy subjects through innovative sensing devices which enable fast yet accurate evaluations of the above parameters. A statistical analysis was carried out to determine significant differences between the facial areas investigated and clusters of statistically-indistinguishable areas. We found that water content was higher in the cheeks and neck and lower in the lips, whereas trans-epidermal water loss had higher values for the lips and lower ones for the neck. In terms of thickness the dermis exhibited three clusters, which, from thickest to thinnest were: chin and nose, cheek and forehead and lips and neck. The epidermis showed the same three clusters too, but with a different ordering in term of thickness. Finally, the stratum corneum presented two clusters: the thickest, formed by lips and neck, and the thinnest, formed by all the remaining areas. The results of this investigation can provide valuable guidelines for the evaluation of skin moisturisers and other cosmetic products, and can help guide choices in re-constructive/cosmetic surgery.

Measurement of skin hydration with a portable device (SkinUp® Beauty Device) and comparison with the Corneometer®

BACKGROUND

Epidermis hydration measurement is an important tool to assess its health. SkinUp^® is a portable device that measures moisture and oil levels of skin through impedance method, it is cheap and has small dimensions, but this equipment has not yet been cited in the scientific literature. Thus, the objective of this work was to validate SkinUp^® equipment by comparing its results with Corneometer^® CM825.

MATERIALS AND METHODS

Twenty subjects had skin hydration measurement on forearm, cheeks, and forehead. Measurements obtained with the two instruments were correlated by calculating the Pearson correlation coefficient and the P-value significance. The sensitivity of the equipment to different regions and treatments and their accuracy were also evaluated.

RESULTS

Positive correlations between equipment were found for skin hydration, with P ≤ .001. Both instruments presented high sensitivity to the different treatments (P < .001). When sensitivity to different regions was evaluated, both showed greater hydration in the cheek and forehead when compared to the forearm (P < .005). The measurements between the cheek and forehead showed no significant difference when compared to each other. In addition, the two devices have good repeatability in the measurements.

CONCLUSION

These results indicate that SkinUp^® can be used in the future for skin analysis in in vivo assays.

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.