In humans, roughly 1.6 to 5 million sweat glands are found in the skin, and the amount varies between individuals as well as anatomic sites. The region with the greatest sweat gland density is the palms and soles of the feet, which contain 600–700 sweat glands/cm2. The primary function of sweat glands is to keep the core body temperature at approximately 37 °C by releasing sweat in a hot environment or during physical activity.
Sweat glands are innervated by neurons, so the process of sweating is controlled by the central nervous system. Thermosensitive neurons in the brain can detect the internal body temperature and external skin temperature, instructing sweat glands to respond accordingly to maintain a constant core body temperature. When an increase in temperature is detected, sweat is induced to cool the skin, and internal body temperature decreases when the sweat evaporates from the surface of the skin. Therefore, sweat glands are essential in keeping the body temperature constant.
A core body temperature higher than 40 °C can result in protein denaturation and apoptosis. Physically, it can lead to hyperthermia, commonly known as heat exhaustion or heat stroke, which can be fatal.