paradoxical cold and heat

The sensation of "paradoxical cold and heat" refers to a phenomenon where cold receptors can be activated by high temperatures, leading to a sensation of cold when touching a hot object. This occurs because certain transient receptor potential (TRP) channels, specifically TRPM and TRPA, are known to respond to cold, while TRPV channels respond to warmth and heat.123

When skin temperatures exceed 45°C (113°F), cold-sensitive nerve fibers can be paradoxically activated, causing a brief sensation of cold. This is distinct from the sharp pain caused by extreme cold due to ice crystal formation or the burning sensation from the "thermal grill illusion," where alternating warm and cool stimuli can trick the brain into perceiving a burning sensation. Thermoreceptors are crucial for animals to detect thermal changes and adjust their internal environment, enabling survival in varying temperatures.14