Sweat it. Sniff it. We might be communicating positive or negative emotions through the smell of our sweat. A study revealed that whenever we experience a particular emotion, we are producing chemical compounds or chemosignals and we release them through our sweat. Thus, others unknowingly receive these chemosignals and interestingly, experience similar emotions whenever they smell our sweat.
Previous research has already determined that people can communicate negative emotions related to fear and disgust through detectable regularities in the chemical composition of sweat. A team of researchers spearheaded by Gün Semin, psychological scientist at Utrecht University in the Netherlands, examined whether this same phenomenon is true for positive emotions, specifically by determining whether sweat taken from people in a happy state would influence the behaviour, perception, and emotional state of exposed people.
The researchers conducted a two-part experiment. The first part centred on collection of sweat samples while the second part centred on exposing selected participants to the collected samples. In addition, the study was double-blind, such that neither the researcher nor the participant knew which sweat sample the participant would be exposed to at the time of the experiment.
In the first part, the researchers recruited 12 Caucasian males who subsequently provided sweat samples for the study. These participants did not smoke, drink alcohol, or take any medications, and had no diagnosed psychological disorders. They were also barred from sexual activity, consumption of smelly food, and excessive exercise during the study.
Three phases characterised the entire process of collecting sweat samples. For each phase, participants were asked to watch a video clip intended to stir a particular emotional state—fear, happiness, and neutral—while wearing absorbent pads in their armpits. They also completed a measure of implicit emotion, in which they were asked to view Chinese symbols and rate how pleasant or unpleasant each one was.
In the second part, the researchers also recruited 36 Caucasian females with no respiratory illness, psychological disorders, or other health conditions. These participants were the receiver of the provided sweat samples. Accordingly, the researchers based this gender preference from the fact that women generally have better sense of smell and a greater sensitivity to emotional signals than men.
While seated in a chair and fixed on a chin rest, in addition to an ongoing video recording for facial expression data collection, each female participant was exposed to each type of sweat sample. There was a five minute break in between sample exposures.
Analyses of the facial expression data revealed that the female participants who were exposed to “fear sweat” registered greater activity in the medial frontalis muscle. This activity is observable in fear expression. Moreover, exposure to “happy sweat” registered more facial activity commonly observed in happiness expressions.
Further data revealed that female participants exposed to “happy sweat” demonstrated a more global focus in perceptual processing tasks, in line with previous research showing that participants induced to experience positive mood tended to demonstrate more global processing styles.
Nonetheless, the results of the study ultimately suggest that there is a behavioural synchronisation between the sender and receiver. While preliminary, these results also suggest that we communicate positive and negative emotional states through distinct chemosignals. The smell of our sweat serves as a medium for affecting similar emotions. In other words, fear or happiness may be communicated chemically. These results could have broader implications, especially commercial applications.
Further details of the study are in the article “A Sniff of Happiness” published in the journal Psychological Science. Coauthors include Jasper H.B. de Groot of Utrecht University; Monique A.M. Smeets of Utrecht University and Unilever Research and Development; and Matt J. Rowson, Patricia Bulsin, Cor G. Blonk, and Joy E. Wilkinson of Unilever Research and Development. Unilever Research and Development provided funding from the study.