numbing

Numbness is a sensory category in which oral touch is reduced or altered, distinct from bitterness and pungency. A literature account says spilanthol, found in toothache plant and other sources, and structurally related unsaturated fatty-acid amides evoke several somatosensory qualities: pungency, tingling, buzzing, numbness, salivation, and cooling. Numbness is one of these. The account is a literature summary in an introduction; the study itself used mouse cells and did not measure human time-intensity responses.

In a time-intensity and temporal-dominance evaluation by a trained human panel of Chinese huajiao (Zanthoxylum bungeanum), numbness was also among the measured sensations, and samples with higher Scoville values have been reported to have longer-lasting numbness. This was checked only at the abstract level; per-sample values could not be confirmed from the abstract.

For the fruit of makhwaen used in northern Thailand, a government extension article describes a strong aroma and mild heat (รสเผ็ดร้อนเล็กน้อย), as well as a mixed pungent-and-numbing quality called 『เผ็ดชา』 (in translation: "numbing-spicy"). It says using the fruit in cooking makes the tongue tingle and feel numb, a sensation called 『เด้าลิ้น』 (in translation: "tongue bounce or rebound") in northern Thai speech. This is an explanatory extension article, not a sensory-panel measurement, and this source does not analyze whether specific chemicals such as sanshools cause the sensation.