Not only is there a smell of fear, but this also renders fear “contagious”: People who smelled armpit fear became physiologically aroused (increased galvanic skin response)

A Path to Identifying the Smell of Fear. Shiri Karagach et al. Chemical Senses, 2020, Vol 45, 699–804, The Eighteenth International Symposium on Olfaction and Taste (ISOT XVIII) and the Fifty-First Association for Chemoreception Sciences Annual Meeting (AChemS LI), Aug 2020, doi:10.1093/chemse/bjaa061

Rolf Degen's take: https://twitter.com/DegenRolf/status/1326592651186085889

Abstract: Several studies found that body odor collected from human participants in a state of fear has pronounced behavioral and physiological effects on conspecifics. Body-odor can arise from sweat emitted primarily from two types of glands: eccrine and apocrine. The relative contribution of these sources to human social chemosignaling remains unclear. The importance of understanding this is not only the basic building blocks of social chemosignaling behavior, but it is a critical methodological step towards the holy grail of social chemosignaling research, namely identifying the molecules at play. To identify social chemosignals, from where should we collect emissions? From eccrine or apocrine regions? To address these questions, we collected eccrine (lower back)and apocrine (armpit) sweat from ~750 individuals in two states: Fear - first-time military parachuting, and Control - physical exercise. We then exposed ~25 experimental participants to these sources. We found that relative to control, fear sweat was perceived as more intense, less pleasant and rated as more fearful. Measurement of the galvanic skin response (GSR), a robust measure of autonomic arousal, implied pronounced GSR responses to armpit but not lower-back fearsweat. In other words, not only is there a smell of fear, but this also renders fear “contagious”: People who smelled armpit fear became physiologically aroused. Given that armpit sweat is a potential meaningful source for chemosignaling, further chemical analysis was facilitated with gas-chromatography mass-spectrometry (GC-MS). Principal-component analysis (PCA) uncovered clear separation between armpit fear and control sweat. This allowed us to identify a limited bouquet of chemicals evident in fear but not control sweat.