Why Do We Sweat?

Quick Answer

Sweating cools the body through evaporative heat loss when internal temperature rises above its set point.

The Full Story

Humans are among the most efficient sweaters in the animal kingdom, with 2 to 4 million eccrine sweat glands distributed across the skin. When the hypothalamus detects a core temperature rise — from exercise, heat, or fever — it signals these glands to secrete a dilute saltwater solution onto the skin surface. As each gram of sweat evaporates, it absorbs about 2,430 joules of heat from the skin, cooling the body. This system allowed early humans to hunt by persistence running in the African savanna, outlasting prey that could only cool down by panting.

Key Facts

1.An average person produces about 0.5 to 1 litre of sweat per day, but during intense exercise this can exceed 2 litres per hour.

2.Sweat itself is nearly odourless; body odour comes from bacteria breaking down sweat components on the skin.

3.Humans have the highest density of sweat glands of any primate.

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