Table 1.

Commercial Hydration Devices.

Device	Company	Technique	Description of Measurement Process
Corneometer (CM825)	Courage and Khazaka	Conductance	Measures dielectric constant changes caused by skin surface hydration changing the capacitance of a precision capacitor. Correlation of 0.99 between analogue and digital versions [30]
MoistureMeterSC	Delfin Technologies	Capacitance	Applies an electromagnetic field to measure the skin’s dielectric constant. It is not affected by formulation electrolytes [31]
Skicon-200EX		Conductance	Measures the conductance of a single high-frequency current. Correlations of r = 0.98 with analogue Corneometer and r = 0.97 with digital Corneometer [32]
Nova Dermal Phase Meter (Novameter)	NOVA Technology Corp.	Impedance	Measures skin impedance to provide a non-invasive and objective measurement method to quantify the relative hydration of the skin [35].
SkinChip	L’Oreal	Capacitance	Based on an active capacitive pixel-sensing technology where the effective feedback capacitance is modulated by skin–sensor contact. Correlations of r = 0.69 versus Corneometer [40]
MoistureMap	Courage and Khazaka	Capacitance	Its sensor is based on capacitive-touch imaging technology to give graphical information on the skin hydration distribution and topography [50]
Surface Characterizing Impedance Monitor (SCIM)	U.S. Pat. No. 5353802	Impedance	Integrates readings taken at different frequencies of the applied alternating current to generate impedance-based values [51]
Tewameter	Courage and Khazaka	Open-Chamber Transepidermal Water Loss (TEWL)	Measures TEWL based on the diffusion principle in an open chamber to measure moisture at two sites. Correlation with gravimetric measurements, r = 0.7666 [52]
DermaLab	Cortex Technology ApS	Open-Chamber TEWL	Uses relative humidity and temperature sensors in an open chamber for a continuous readout of TEWL. ICC = 0.81 and r = 0.93 versus Tewameter [53]
Evaporimeter	ServoMed	Open-Chamber TEWL	Measures TEWL by estimating the vapour pressure gradient of water adjacent to the skin surface. Correlation of r = 0.97 versus Tewameter [54]
Vapometer	Delfin Technologies	Closed-Chamber TEWL	Monitors the increase in relative humidity inside the chamber to automatically calculate the evaporation rate. Correlation with gravimetric measurements, r = 0.763 [55]
Biox Aquaflux	Biox Systems	Condensed-Chamber TEWL	Measures TEWL using a condenser that continuously removes water vapour by conversion to ice [56]
Dermal Torque Meter (DTM)	Dia-Stron	Skin Elasticity	Induces a given amount of stress using a rotating disc on the skin, and then measuring the angular displacement of the skin deformation. Correlations of r = 0.54 with Cutometer for elastic deformation [57]
Twistometer	Dia-Stron	Skin Elasticity	Involves the induction of a given amount of stress using a rotating disc adhered to the skin, and then measuring the angular displacement of the resulting skin deformation [12]
Cutometer	Courage and Khazaka	Skin Elasticity	Uses a suction-based measurement principle using negative pressure and an optical measuring system. Correlations of r = 0.54 with DTM for elastic deformation [58]
Dermaflex	Cortex Technology	Skin Elasticity	Uses a suction-based measurement principle with a proportional strain method rather than the disproportional superficial system [59]
Raman Skin Analyser 3510	RiverD International B.V.	Confocal Raman Microscopy	A sample is illuminated for Raman scattering to occur, where the energy of the light is transferred to a molecule, exciting its vibrational modes to give a direct spectrum [60]