There are three kinds of sweat: sweat from heat, sweat from exercise and sweat from stress. Of the three, stress sweat is the hardest to control and gives off the foulest stench. If you have trouble keeping your cool in stressful situations, it’s not just bad luck—you’re biologically programmed to stink under pressure.
Under normal circumstances, perspiration is meant to cool you down so you don’t overheat. When it’s hot or you’re exerting yourself physically, your temperature gradually rises. Your body’s internal thermostat, located in the hypothalamus, eventually recognizes that it better do something to chill you out and triggers the release of neurotransmitters that instruct millions of eccrine (sweat) glands all over your body to produce sweat. As the sweat evaporates, it carries heat away from you, cooling you off. Voilà.
It’s a whole different story when you are about to give a speech, stuck in traffic on the way to the airport, or waiting for your blind date to show. Nervous excitement causes adrenaline and cortisol to rush into the bloodstream, raising your heartbeat and unleashing an instantaneous torrent of sweat from your eccrine glands and other glands called apocrine glands, located in your armpits and pubic region. (Apocrine glands are also found in a third location, the ear canal, where they help keep ear wax waxy.)
There’s no warm-up period. You go from zero to sweaty in seconds flat. Suddenly you’re drenched—and that stresses you out even more. “If you’re standing out in 100-degree weather, it’s a gradual increase, and anyone else is going to sweat. You expect it,” says Susan Biehle-Hulette, Ph.D., a biochemist at Procter & Gamble. “Conversely, if all of a sudden you have to give a presentation and you’re put on the spot, you are then the only one sweating.”
And stinking. Any sweat can cause body odor, but the smell of stress sweat comes on real strong, real fast. When you sweat, you feed the bacteria that live naturally on your skin. Their digestion produces an unpleasant aroma that we all know as B.O. How bad the B.O. is depends in part on what and how much you feed them. While eccrine secretions are 99 percent water with some electrolytes tossed in, apocrine sweat is 20 percent fats and proteins. If you were to put it in a glass it would look like coffee creamer. Bacteria go nuts for the stuff. They feast on it, and you’re left wafting the pungent aftermath.
Research into the function of the apocrine glands suggests an evolutionary role in the fight or flight response. “When a lion is chasing you, you want to smell bad so they don’t eat you,” Biehle-Hulette explains. Studies also show that people can subconsciously recognize the difference between fear sweat and regular sweat, suggesting that it can act as a peer-to-peer danger alert system.
In our largely lion-free world, however, the protective value of stank is nil, while the social consequences are high. When Biehle-Hulette led the research team that developed Secret’s Clinical Strength antiperspirant deodorant, the top concern they heard from women in their focus groups was the smell of stress sweat. So they designed the product to address the problem at a chemical level, not just mask the funk with fragrance. Secret’s secret is a patented donut-shaped molecule that physically traps odor molecules, like Febreze for pits.