Studies always highlight that the hydration is the most sensitive claim for the consumers. Since the superficial layers of the epidermis, investigators gradually go through the different skin layers analysing the overall skin hydration. Skin hydration, as a gold claim, is often evaluated for a large range of product functionalities such as aging, soothing, mechanical properties, pollution, radiance and complexion…

The best-known measurement principle uses the skin electrical properties to assess the moisturizing effect of the Stratum Corneum, the epidermis and the dermis. The test indirectly measures either the capacitance, the impedance or the permittivity with specific characteristics to study the several layers of the skin. The measure is easy, fast, reproducible and well established and can be carried out in contrasting climate and various ethnicities:

• Stratum Corneum: Corneometer® (C+K), Dermalab, Epsilon (Biox), MoistureMeter SC, Skicon-200, DPM 9003,
• Epidermis: MoistureMeterEpiD
• Dermis: MoistureMeterD

Quantitative and qualitative alternatives measures have emerged with different levels of technology:

• Micro-topography analyse: MoistureMap® (C+K), Epsilon (Biox),
• Infra-red Spectroscopy: Dermo,
• TEWL for Trans Epidermal Water Loss, indirect method: Tewameter® TM 300 and Nano (C+K), Aquaflux (Biox), Dermalab, Evaporimeter, Vapometer…
• The cutaneous surface visualisation: Visioscan (C+K), Dermalab, Hirox, and all other camera systems.
• The scoring by technician experts and dermatologists represent a valuable approach giving, with specific scales, many information through visual and tactile objectivation.

Hydration can be objectivated using very high-tech and non-invasive methods through various ways:

• The skin structure visualization: MPT Flex Optical Multiphoton Tomography, Scanner, Vivascope and Vivosight and Laser Confocal microscopy,
• The skin molecular water content with Confocal microscopy LBRAM 800 and Raman spectroscopy gen2-SCA.
• The latest technology developed is LC-OCT 3D microscopy enables both quantitative and visual results.

Sensory analysis by trained panels or naïve subjects give scientific objectivation can be combined with face emotional analysis. Then consumer testing under normal conditions contribute also to this assessment.

The skin studies include scalp ones. For the haircare different methods have been developed to substantiate this claim through combing, friction, traction, structure or gravimetry analysis. We advise you to take time with the CRO’s to design each protocol and define precisely, the inclusion criteria, the time measurements, treatment conditions, the optimal device… You never waste time briefing these essential elements.

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