What Is Sweat?
On one hand, we all know it when we feel it. Sweating (also called perspiration) is that damp feeling on our skin when it’s hot outside, or when we have been working hard. We’ve all felt it many times.
On the other hand, there’s a lot about sweating you probably don’t know yet. Did you know everyone has between 2 million and 4 million sweat glands? Do you know why waiting for a job interview makes your palms slick? Did you know that even when you’re unaware of it, your body is sweating just a little?
In this article, learn some of the many causes of sweating, from hot flashes to falling in love. You’ll also discover a condition known as hyperhidrosis—excessive sweating—along with health tips for treating it. So find a cool, well-ventilated place and read on for more on the steamy causes of perspiration.
Probably the best-known cause of sweating is heat. Any time the thermometer soars you know you’ll be battling huge temperatures, and your first line of defense against heat is sweat. Sweat’s entire purpose is to keep our warm-blooded bodies from overheating. The scientific term for this is “thermoregulation.”
The key to sweat’s cooling power is evaporation. Evaporation is what happens when a liquid becomes a gas. In this case, the sweat from your skin evaporates into the air around you. Sweat needs some of the heat from your body in order to change from a liquid to a gas. That’s called heat transfer. And that’s basically why you cool down when you sweat—the sweat carries off some of your body temperature as it evaporates.
That also helps explain why sweating doesn’t work as well when the air around us is humid. On humid days, the air is already full of moisture. That means your perspiration has more difficulty escaping your skin. And that’s why more humid weather feels hotter to us, even if the overall temperature is cooler than in drier weather.
Under normal circumstances, you can sweat out a maximum of 1.5 liters every hour—a little over six cups. But in very hot, humid places like jungles, that changes. You can adapt after a few weeks in such conditions to sweat out as much as 3.5 liters per hour—almost a gallon!
It should be fairly clear why it’s so important to your health to drink water when you’re sweating that intensely. Not only do you need water for all kinds of other purposes, but running out of perspiration when you need it can be hazardous to your health. You only need to lose about 2 percent of your body fluid before signs of heat exhaustion set in. And if your core temperature rises above 103 degrees, that can be fatal.