Differences in the chemesthetic subqualities of capsaicin, ibuprofen, and olive oil.

Chemesthetic sensations elicited by ibuprofen, extra-virgin olive oil, and capsaicin were compared to quantify perceptual differences between known agonists of TRPA1 and TRPV1. Extra virgin olive oil contains a phenolic compound, oleocanthal, which is thought to share unique chemesthetic qualities with the nonsteroidal anti-inflammatory drug, ibuprofen. Pilot work suggested participants had difficulty distinguishing between multiple chemesthetic subqualities (e.g., burn, sting, itch, tickle, etc.) in a multiattribute rating task. Here, we assessed overall irritation via direct scaling, and a check all that apply task was used to collect information about chemesthetic subqualities over time. Replicated ratings were collected at discrete intervals using the generalized labeled magnitude scale to generate time-intensity curves; maximum intensity (Imax) and area under the curve were extracted for each participant. Intensity responses varied substantially across participants, and within a participant, the relationship was strongest between ibuprofen and olive oil. However, there were also positive, albeit weaker, correlations between capsaicin and ibuprofen and capsaicin and olive oil. The correlation found between olive oil and capsaicin may suggest the presence of unknown TRPV1 agonists in olive oil. This view was also supported by the qualitative data: capsaicin was described most often as burning and warm/hot, whereas ibuprofen was numbing and tickling. Olive oil shared characteristics with both capsaicin (warm/hot) and ibuprofen (tickle).