A trip to the gym can leave some people’s shirts unusually soaked. For others, shaking hands with the boss can be a physically stressful moment.

The reasons some people sweat a lot while others stay dry aren’t completely understood. Still, one expert, Harmik J. Soukiasian, chief of thoracic surgery at Cedars-Sinai Medical Center, in Los Angeles, has some wisdom on the matter. Dr. Soukiasian also heads Cedars-Sinai’s clinical team for hyperhidrosis, or excessive sweating.

To Sweat Is Human

Sweating is a natural process. “If it’s too hot, you sweat, and as the water evaporates, you cool down,” he says. Perspiring serves other functions, too. It helps keep the skin hydrated. And it helps maintain the body’s balance of fluids, though in doing so it removes electrolytes and salts. “You need to replenish them with something beyond water if you are exercising or sweating heavily,” he says.

Studies have shown that less-fit people tend to sweat more than gym rats because their bodies require more work to cool down, Dr. Soukiasian says. However, fit people start sweating earlier during equivalent exercises. That is likely because people who are accustomed to exercise have bodies that run efficiently. They start to cool down as soon as their core temperature rises, he says.

Nervousness can tip the body into survival mode, which can trigger the release of adrenaline, boost a person’s heart rate and send sweat glands into overdrive. “Emotional sweating is part of the ‘fight-or-flight’ response and is normal,” Dr. Soukiasian says. But “sweating while sitting on your couch and listening to classical music is not the norm.”

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