tingling

「チクチク感」 (in translation: "tingling"), perceived as recurring numb-like stimulation, belongs to oral touch and chemesthesis and is distinct from taste in the narrow sense. An account of spilanthol lists it among somatosensory experiences including prickling, buzzing, and numbness. This is a literature-review classification, however, not a direct measurement in humans.

In a human sensory evaluation of huajiao, tingling was one of the measured sensations and was reported to be stronger in more intense samples. A separate experiment with solutions of hydroxy-α-sanshool compounds, which contribute to huajiao stimulation, found that at low concentration tingling characteristically began at the tongue tip and ended at the lips. At intermediate concentration, tingling, astringency, vibration, and numbness spread over time from the tongue tip to the sides of the tongue, lips, palate, oral mucosa, and tongue surface.

Another experiment reported that huajiao-induced tingling on human lips matched a mechanical vibration at the fingertips of approximately 50.0 Hz. This frequency is described as overlapping the response range of RA1, a type of nerve fiber for skin touch, but the estimate is the mean from a frequency-matching experiment with 8 participants. After prolonged mechanical vibration had adapted this tactile fiber, the perceived frequency of huajiao tingling fell, just as that of mechanical vibration itself fell. Separately, sustained mechanical pressure was reported to reduce tingling intensity to a mean 24.7% of baseline.

Human experiments confirmed that the tingling induced by sanshool was not weakened even after pretreatment desensitizing TRP channels responsive to capsaicin and mustard oil. The phenomenon itself was observed, but other sources disagree about which receptor mechanism produces the tingling.