Could you run out of sweat?

Asked by: Derrick Rhodes, Ramsgate

Sweat doesn’t sit in a separate reservoir or fuel tank that can be temporarily drained dry. The eccrine glands in your skin take fluid directly from the plasma in your blood; in effect sweat glands are a kind of modified, leaky capillary. At maximum levels of production, the human body can sweat as much as three litres per hour. That’s equivalent to your entire blood volume in just an hour and forty minutes. But if you didn’t drink you would die from hypovolemic shock or heart failure due to electrolyte imbalance before then.

Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.