People sweat from the day of birth onward. Generally, the amount of perspiration is small, just enough to keep the body cool in a process called “thermoregulation,” whereby skin is cooled as perspiration evaporates. When the ambient temperature exceeds resting body temperature or during exercise when muscle activity increases the body’s core temperature, perspiration increases.
Hormones
Humans have two types of sweat gland, eccrine sweat glands and apocrine sweat glands. Eccrine sweat glands function from birth, while apocrine glands only become functional at puberty when the body begins to produce higher levels of androgens, the so-called “male” hormones.
A hybrid of the two types of sweat gland, called apoeccrine glands, develops at puberty. These glands are mostly located in the axillae (underarm region) and produce approximately 10 times the amount of perspiration that eccrine glands produce, according to the American Academy of Dermatology.
When a person’s hormone levels change, such as at puberty or–in women–during menopause, increases in perspiration can occur. The American Academy of Family Physicians relates that in the case of “hot flashes” in menopausal women, fluctuating concentrations of endogenous estrogen, the “female” sex hormone produced as part of the menstruation cycle, may be the underlying cause of increased sweating.
Heat
Resting body temperature in humans has a small range. When sensors in the body alert the brain that either core body temperature is increasing, as from exercise or fever, or that ambient temperatures are increasing, the body begins a process that rids itself of heat. Nikos Drakos of the University of Leeds explains that individual cells release heat into the interstitial fluid, the fluid that surrounds them. The heat is then transferred to the blood stream. Blood vessels in the subcutaneous portion of skin dilate to increase the amount of heat near the skin’s surface and sweat glands increase output to carry the heat out of the body. The heat is then transferred from skin to the environment during evaporation.
Emotions
Called palmar/plantar sweating, emotional sweating mostly occurs on the palms of the hands and the soles of the feet. In times of high emotion, the body goes into “fight or flight” mode, to prepare itself for physical action. When this happens, the heart beats faster, respiration increases, the liver releases glucose to supply energy to the muscles, pupils dilate and perspiration increases. In their book, “Neonatal Skin: Structure and Function,” authors Steven Hoath and Howard Maibach call this response a “vestigial” response in humans and hypothesize that, as in other mammals, the moisture increases friction with the ground to allow for a quicker getaway.
