The effect of disgust on oral immune function.

Disgust motivates avoidance of pathogen sources, but whether its role in disease avoidance extends into activating the immune system is unexplored. This was tested here by comparing oral immune markers before and after a disgust induction, relative to neutral and negative induction control groups. The disgust group, but not controls, revealed an oral inflammatory response, with increased salivary tumor necrotizing factor alpha and albumin, as well as a down-regulation of immunoglobulin A (SIgA) secretion. It has been hypothesized that disgust evolved in animals to clear toxins from the oral cavity by gaping and increased salivary flow. Our data suggest down-regulated SIgA secretion may be a vestige of this response so as to conserve protein, while the inflammatory reaction may reflect an adaptive response to disease threat, selectively triggered by disgust. The broader implications of these data for a discrete neuro-gut-immune axis are examined.