Oral chemical irritation: psychophysical properties

Concentration series of four oral chemical irritants derived from spices (capsicum oleoresin, vanillyl nonamide, piperine and ginger oleoresin) were evaluated for perceived intensity and perceived areas of sensation over time. Growth of sensation with concentration was described by power function relationships and decrements in sensation over time were described by exponential decay. Peak sensation intensity was correlated with stimulated salivary flow rate. The number of oral areas reported as irritated increased with concentration and decreased over time. While some differences were observed among compounds in the areas of stimulation, the dorsal tongue surface and tongue edges were highly responsive to all compounds. A sequential desensitization was observed, in which stimuli were perceived as less strong when following a stronger irritant than when following a weaker one.