The palms of the hands serve as effective thermoregulatory surfaces for the human body, allowing holding cold objects to lower body temperature and reduce sweating and blushing.
"The palms of your hand are thermoregulators for your body. Anybody who's ever held warm coffee or tea on a cold morning has felt themselves warm up. I will always hold something cold before I speak and it helps cool me down. I blush and perspire less." (said at 2:20:05)
The biological basis of the claim is partially accurate: the palms of the hands (glabrous skin) contain arteriovenous anastomoses (AVAs) that allow for substantial heat exchange, and specialized palmar cooling devices can attenuate the rate of core body temperature rise during exercise or heat strain. However, the claim is overstated: simply holding cold objects often induces local vasoconstriction, preventing effective heat extraction. Furthermore, studies of simple palmar cooling have found no significant reduction in core body temperature or sweat rate, and there is no robust scientific evidence showing that holding cold objects reduces emotional or autonomic blushing.
- supports: A method to reduce heat strain while clad in encapsulating outerwear. (Journal of occupational and environmental hygiene 2018)
"The glabrous skin regions of the hands, face, and feet are portals for direct heat transfer between the body core and the external environment." (abstract, passage verified)
pubmedfull study (doi) - supports: Bioheat Transfer Basis of Human Thermoregulation: Principles and Applications. (Journal of heat transfer 2022)
"Humans have evolved a particular vascular structure in glabrous (hairless) skin that is especially well suited for heat exchange. These vessels are called arteriovenous anastomoses (AVAs) and can vasodilate to large diameters and accommodate high flow rates." (abstract, passage verified)
pubmedfull study (doi) - contradicts: Effects of palm cooling on thermoregulatory-related and subjective indicators during exerc… (Journal of thermal biology 2024)
"Palm cooling at 12°C and 0°C improved thermal sensation and thermal comfort during exercise in a hot environment, although there was no effect on core body temperature, sweating, and cardiorespiratory function." (abstract)
pubmedfull study (doi)