Why do our fingers get wrinkly in the bath?
For grown-ups: the science
Wet fingertips wrinkle because nerves tell tiny blood vessels underneath to get narrower, pulling the skin into ridges.
Finger wrinkling after immersion is an active nervous-system response. Wet skin triggers sympathetic nerve activity that constricts blood vessels beneath the fingertips, changing the tissue volume and pulling the surface into wrinkles. The leading hypothesis is that these wrinkles can improve handling of wet objects, though the exact evolutionary benefit remains under study.
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Transcript
Your fingers splash in warm bath water. After a little while, why do little lines appear on them?
When your fingertips stay wet, nerves in your skin notice. They send a message to tiny blood vessels underneath.
The tiny blood vessels get narrower. That gently pulls the fingertip skin down into little ridges and dips.
The ridges may help you hold wet things, like tire treads help tires grip wet roads. Scientists are still studying this idea.
So, wrinkly fingertips are something your body makes when they have been wet for a while.