Sweating

Sweating, or perspiration, is the secretion of sweat from sweat glands in the skin. In humans, sweating serves primarily to regulate body temperature through evaporative cooling, but it also helps remove certain waste products and maintain skin hydration. The amount of sweating varies with environmental conditions, activity, and individual physiology.

Sweat is produced by eccrine glands, which are distributed over most of the body, especially on the palms, soles, and forehead. Apocrine glands, found mainly in the armpits and groin, secrete a thicker fluid that is initially odorless but can develop odor when exposed to skin bacteria. The secretion from eccrine glands is the principal source of thermoregulatory sweat.

Human sweat is about 99% water and contains electrolytes such as sodium and chloride, as well as small amounts of urea, lactate, ammonia, potassium, and enzymes. The pH typically ranges from slightly acidic to neutral. Odor arises mainly from bacterial breakdown of sweat components, especially in apocrine-rich areas.

Sweating is controlled by the sympathetic nervous system via cholinergic nerves that stimulate eccrine glands. It increases with heat exposure, physical exertion, fever, anxiety, and certain medications. Age, fitness, hydration status, and acclimatization influence sweating patterns.

Abnormal sweating includes hyperhidrosis (excessive sweating) and anhidrosis (reduced or absent sweating). Treatments include topical aluminum-based antiperspirants, oral anticholinergic medications, botulinum toxin injections, iontophoresis, and in severe cases surgical sympathectomy or miraDry. Adequate hydration and electrolyte balance are important during prolonged sweating.