In Vivo Assessment of Skin Hydration and Moisturisation Using a Multi-Wavelength Optical Sensing Wearable.

Skin hydration is pivotal determinant of skin barrier functionality, influencing its aesthetic, functional, and overall structural integrity. Clinically, skin hydration assessment is vital for the detection, prevention and management of a spectrum of conditions, from dryness and inflammation to eczema and atopic dermatitis. This research employs an innovative multi-wavelength optical sensing device that has been developed to enhance our comprehension of optical-based skin hydration measurement capabilities. By probing the absorption spectra of human skin, this technology extends beyond the surface, enabling a deeper analysis transcending the epidermis. Of particular note are the characteristic absorption peaks associated with water content in skin cells, notably at 970 nm and 1450 nm. Previous ex vivo experiments have been carried out, in which robust correlations were found during desorption tests on porcine skin using the optical sensor alongside reference techniques. This preliminary study employs a small-scale research protocol assigned to participants, involving the moisturisation of a forearm over a 7-day period, while the other forearm served as an untreated control. The research findings highlight the heightened sensitivity and accuracy of the developed optical device in determining moisture levels and water presence variations at the specified wavelengths. Differential gradients revealed an over 50 times larger incremental response for the moisturised forearm over the control forearm. Corroborating linear regression analysis against the Corneometer was confirmed with moderately strong inverse correlations (R= -0.391, -0.607, -0.741, -0.438), enhancing the validity and measurement accuracy of the developed optical device. This research advances our knowledge of skin health and paves the way for refined skin diagnostics and targeted development of therapeutic interventions.