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How did scientists discover warm spots and cold spots in human skin?

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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.

Scientists discovered warm and cold spots in human skin through studies of sensory physiology, which revealed that thermal sensations are associated with the stimulation of localized sensory areas. This discovery, reported in 1882, established that specific, discrete points in the skin are selectively sensitive to either warm or cool stimuli.12

These findings were part of early investigations into human sensory physiology that identified the existence of these spotlike receptive fields. While early research relied on these observations of localized sensitivity, later advancements in electrophysiological methods—introduced in 1936—allowed scientists to record electrical impulses from single thermosensitive nerve fibers. By using microelectrodes to study these fibers, researchers were able to characterize the properties of thermoreceptors and confirm their role in detecting temperature variations.132

Modern research has further refined this understanding by identifying the molecular mechanisms, such as transient receptor potential (TRP) channels, that allow these receptors to respond to thermal changes.12