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This paper describes a method for the comparison of the cooling capability of over-the-counter devices for skin tags removal. The comparison is performed by measuring the heat flux produced by the gas identified assessing the temperature difference across an element with a known thermal resistance; the temperature reached at the interface between the device and the heat-flux meter is also analyzed, although it is different from that of the skin during the treatment. The measurement accuracy has been experimentally evaluated and, with a confidence interval of 95%, is better than 6% for heat-flux measurements and lower than 0.3 °C for temperature measurements. The instrument allowed comparing the thermal efficiency of 19 dimethyl ether and propane devices of different types (dispenser, spray, and foam). Results are by far more reliable than those obtained with tests performed on subjects, where the intrinsic skin thermal properties variability prevents from assessing differences smaller than 30%. [ABSTRACT FROM PUBLISHER]

The skin–contact thermal resistance is a parameter that allows evaluating, in steady condition, the heat flow at the interface between the skin and a rigid surface at a known temperature. At the current state of the art, it is evaluated with empirical equations and is known to be dependent on the contact pressure, on the surface characteristics, and on the skin conductivity. The need to measure skin and contact thermal resistance with low uncertainty led to the realization of the device described in this paper. The instrument—based on the principle of the thermoflowmeter—has been designed with the goal of minimizing the measurement uncertainty with contact temperatures ranging between 12 ^\circ\C and 27 ^\circ\C and contact areas from 50 to 314 \mm^2. The device allows varying and controlling the interface pressure and temperature that, according to existing literature studies, are likely to influence the skin thermal properties. The different temperatures needed for the evaluation of the thermal resistance are measured with individually calibrated thermocouples. The metrological characterization of the flowmeter was performed under vacuum, and the effect of convective heat exchanges in normal operation was modeled and compensated. Measurement repeatability and reproducibility were assessed by measuring the thermal resistance of plastic materials in operational conditions. Preliminary tests showed that the skin–contact thermal resistances measured in different conditions are compatible with the theoretically evaluated ones, with improvement in uncertainty due to direct measurement. [ABSTRACT FROM PUBLISHER]