This is what’s known as a human emotional chemosignal: a subtle chemical cue that lives in sweat that carries information about an individual’s emotional state. According to a foundational 2020 study published in Philosophical Transactions of the Royal Society B, fear can actually change the chemical composition of sweat, and in measurable ways, at that.

— Read more in A Biologist Explains How The Human Brain Evolved To ‘Smell Fear’ at Forbes.