If you're happy and you know it, sweat it out.
When you experience joy, you produce chemical compounds that others pick up on when they smell your sweat, according to a small study just published in the journal Psychological Science. Those chemicals create a contagion effect, so that your happy sweat can make others feel happier, too.
"In a way, happiness sweat is somewhat like smiling -- it is infectious," said senior study researcher Gün Semin, a psychological scientist at Utrecht University in the Netherlands, in a statement.
To study the phenomenon, researchers had 12 men watch three videos, each clip designed to incite a fearful, happy or neutral emotional state. They gathered underarm sweat samples from the men after each video, and also had them complete a survey which measured their emotional states. The study leaders then distributed the samples to a group made up exclusively of women, because according to the study's authors, women have a greater sensitivity to smell and emotional cues than men do.
Each of the 36 "sniffers" was exposed to one each of the fearful, happy and neutral sweat samples, with a five-minute break between each vial. Neither the researchers nor the participant knew during the sniff test which sweat sample they were exposed to at the time.
When the women smelled samples of "happy sweat," they showed more facial activity related to smiling compared to when they smelled the other types of sweat, the study found. The researchers noted that when the women were exposed to the happy samples, they also showed "a more global focus in perceptual processing tasks." That means they were able to see the bigger picture of a situation, which aligns with other research that claims positive mood can influence global processing style.
The contagion effect did have its limits -- women who smelled "happy sweat" didn't score as high for happiness on an emotion survey as the sweat donors did, for example. Still, the ability to communicate positive emotions in this way may have served an important evolutionary purpose, the researchers hypothesize.
"If chemosignals of fear may have served to warn [fellow humans], chemosignals produced during positive states such as happiness may have served to facilitate bonding," another of the study's authors, Utrecht psychologist Dr. Jasper Groot, told The Huffington Post.
Here's how it works: Armpit sweat glands have receptors for adrenaline, a hormone produced by the body in response to stress or excitement. Adrenaline is released not only due to negative arousal like fear and stress, but also during experiences of positive arousal, like intense happiness. Though both activate adrenaline, hormone levels may also be different in these two states, explained Groot.
"Eventually these odors could have become associated with happiness-related or fear-related information in the environment -- such as facial expressions or sounds -- co-present during odor release," Groot continued. "The odors could have become signals through learning."
But if the whole concept of getting up close and personal with a happy stranger's perspiration has you feeling squeamish, don't worry: The finding is relatively preliminary, so we may not have a market for Eau de Perspiration quite yet.