Sweat glands are found in the greatest concentration on the palms and soles because the glands keep these surfaces moist, enabling them to provide the most tactile sensation. If the palms and soles are not properly hydrated, the top layer of skin may harden or flake, subsequently reducing sensitivity.
Two types of sweat glands exist: eccrine and apocrine. Eccrine sweat glands are the most numerous, distributed across the entire body, including the palms and soles. These sweat glands are primarily responsible for cooling body temperature by secreting a mixture of water and electrolytes.
Apocrine sweat glands are generally limited to the armpits, nipples, eyelids, ear canals, nostrils and anal/genital regions of primates. In other animals, apocrine sweat glands are more uniformly distributed. These sweat glands secrete a mixture of proteins, lipids and steroids that bacteria feed on, producing a scent.