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Why can hot objects sometimes cause a brief sensation of cold?

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thermoreception in polar bears — Thermoreception Warm-blooded animals, such as polar bears, maintain stable body temperatures and adapt to substantial geographic and seasonal temperature fluctuations. Thermal adaptation is supported by the function of sensory structures called thermoreceptors.

When a hot object causes a brief sensation of cold, it is known as paradoxical cold. This phenomenon occurs because certain sensory spots in the skin are selectively sensitive to cold, and these receptors can be triggered by very high temperatures—specifically, skin temperatures exceeding 45 °C (113 °F)—in addition to their normal response to cooling.123

While thermoreceptors are generally specialized to respond to specific temperature ranges, this "paradoxical" activation happens when a warm stimulus provides an inappropriate or inadequate, yet effective, stimulation of cold receptors. The resulting sensation is a brief, illusory feeling of cold despite the presence of a hot object. This is distinct from other tactile illusions, such as the thermal grill illusion, which involves a more complex central neural interaction between warm and cold receptors that can produce a burning sensation.123