Bruderer, T.; Greco, A.; Ripszam, M.; Callara, A. L.; Gargano, A.; Reale, S.; Vivaldi, F. M.; Biagini, D.; perchiazzi, M.; Lomonaco, T.; Scilingo, E. P.; Di Francesco, F.

Whether humans communicate fear through volatile chemical cues has remained unresolved, despite decades of behavioural and neuroimaging evidence. Here, we identify a reproducible molecular signature of acute human fear, bridging the gap between functional evidence and chemical mechanism. Using a low-background sampling approach combined with multiscale chemical analysis and hierarchical modelling, we link high-dimensional axillary volatilomes to a continuous physiological fear index during immersive virtual-reality fear induction. We uncover a coherent chemical fingerprint in which short- and medium-chain fatty acids (acetic acid, butyric acid, caproic acid, and caprylic acid), the caprylic acid precursor octanal, and acetone increase with fear, while skin-derived volatiles (sulcatone, decanal, geranylacetone) and citraconic anhydride decrease. This coordinated shift reveals a fear-associated reorganisation of axillary emissions consistent with sympathetic metabolic mobilisation, involving altered fatty-acid handling, increased ketone-related processes, and suppression of the resident skin volatilome.