The temperature of uncovered skin does not provide useful information about the blood temperature and blood flow. The information obtained from the same measurement for thermally insulated skin is more significant. In order to measure the temperature of thermally insulated skin, a teflon cylinder, covered by polyethylene layers, was applied on the skin of the hand. The polyethylene layers permit partial transmission of the infrared radiation through it. Preliminary results show that underskin temperature can be obtained from measurements of radiation transmitted through the thermal insulation which was applied to the skin, and that underskin temperature is related to tissue blood flow more than uncovered skin temperature.
"Underskin temperature measurement by infrared radiometry", Proc. SPIE 2084, Biomedical Optoelectronic Devices and Systems, (1 February 1994); doi: 10.1117/12.167306; https://doi.org/10.1117/12.167306