Why do your fingers wrinkle in water?
The Real Answer
Your fingertips wrinkle in water mainly because your autonomic nervous system triggers constriction of small blood vessels in the fingers. That reduces tissue volume beneath the skin and helps pull the surface into folds. The response depends on intact sympathetic nerves, which is why water-immersion wrinkling has been used clinically as a test of nerve function.
Your fingers spend their entire lives staying dry and prepared for work, and then you put them in water for five minutes and they immediately surrender and give up. They literally wave the white flag. Your hands are like soldiers with the worst morale — one splash and they're like 'I'm out, I'm becoming a raisin.'
The Dunce Dynamics Institute Examines Why People Ask This
Wrinkled fingertips look so much like waterlogged skin that simple swelling feels like the obvious explanation. The surprise is that the response depends on working sympathetic nerves, so your nervous system is actively involved.