skin on fingers

The wrinkles that occur in skin after prolonged exposure to water are sometimes referred to as pruney fingers or water aging. This is a temporary skin condition where the skin on the palms of the hand or feet becomes wrinkly.

In recent past the common explanation was based on water absorption in the keratin-laden epithelial skin when immersed in water,^[8] causing the skin to expand and resulting in a larger surface area, forcing it to wrinkle. Usually the tips of the fingers and toes are the first to wrinkle because of a thicker layer of keratin and an absence of hairs which secrete the protective oil called sebum.

In 1935, Lewis and Pickering already found that the skin in the median nerve distribution failed to wrinkle in patients with median nerve palsy. This suggested a mechanism other than simple water absorption. Recent research shows that wrinkling is related to vasoconstriction.^[9][10] Water probably initiates the wrinkling process by altering epidermal electrolyte homeostasis as it diffuses into the porous skin of the hands and soles via their many sweat ducts. Altered epidermal electrolyte homeostasis would lead to a change in membrane stability of the surrounding dense network of nerve fibers and trigger increased vasomotor firing with subsequent vasoconstriction. Vasoconstriction, through loss of volume, leads to negative digit pulp pressure resulting in a downward pull on the overlying skin, which wrinkles as it is distorted.^[11][jargon]

This insight resulted in bedside tests for nerve damage and vasoconstriction. Wrinkling is often scored with immersion of the hands for 30 minutes in water or EMLA cream with measurements steps of 5 minutes, and counting the number of visible wrinkles in time. Not all healthy persons have finger wrinkling after immersion, so it would be safe to say that sympathetic function is preserved if finger wrinkling after immersion in water is observed, but if the fingers emerge smooth it cannot be assumed that there is a lesion to the autonomic supply or to the peripheral nerves of the hand.