Capsaicin, a chemical found in chili peppers, creates a burning sensation once ingested, which can last for several hours after ingestion.
Irritants are typically thought of as chemical agents (for example phenol and capsaicin) but mechanical, thermal (heat), and radiative stimuli (for example ultraviolet light or ionising radiations) can also be irritants.
The oxidized metabolic products of linoleic acid, such as 9-hydroxyoctadecanoic acid and 13-hydroxyoctadecanoic acid, have also been shown to activate TRPV1, the capsaicin receptor, and through this might play a major role in hyperalgesia and allodynia.
Some patients with rhinitis find nasal sprays including plant-derived chemical complexes such as Ginger, capsaicin and tea-tree oil useful.
Capsaicin (derived from Cayenne, Capsicum minimum) "incites irritation without rubefaction"
A number of vanilloids, most notably capsaicin, bind to the transient receptor potential vanilloid type 1 (TRPV1) receptor, an ion channel which naturally responds to noxious stimuli such as high temperatures and acidic pH.