perspiration

Perspiration, or sweating, is the production and excretion of fluid by sweat glands in the skin. The primary purpose is to help regulate body temperature through evaporative cooling. Sweat is mainly water but contains electrolytes such as sodium and chloride, along with small amounts of potassium, urea, lactate, and other compounds.

Two main types of sweat glands contribute to perspiration: eccrine glands, which are widely distributed and produce a dilute, odorless sweat; and apocrine glands, located in the armpits and groin, which produce a thicker secretion that is initially odorless but can develop odor as skin bacteria break down proteins and lipids.

Sweating is controlled by the sympathetic nervous system, predominantly via cholinergic fibers stimulating eccrine glands, with hormonal and other influences on apocrine glands. Thermal stimuli such as heat or exercise trigger increased sweat production, while emotional stimuli can also activate sweating, especially in the palms, soles, and armpits.

Abnormal sweating includes hyperhidrosis, which is excessive sweating beyond what is needed for temperature regulation, often occurring in focal areas such as the underarms or palms or as a generalized condition. Hypohidrosis or anhidrosis refers to reduced or absent sweating. Causes include genetic factors, thyroid disease, diabetes, infections, medications, and nerve or skin disorders. Dehydration and electrolyte imbalance can accompany extensive sweating, particularly in hot environments or during intense activity.

Odor associated with perspiration is largely due to bacterial decomposition of secretions from apocrine glands, especially in the underarms. Understanding sweating involves its role in thermoregulation, its distinct glandular sources, and its potential clinical implications.